My CIS is a complete mess and I need help!
 

Ok, there is a long painful back story here. It starts with this thread that I posted on 4/28/2024). https://forums.pelicanparts.com/porsche-911-technical-forum/1160979-its-time-air-box-replacement.html#post12240127

So I had a backfire that separated my air box back in April when I was first bringing the car out of storage. (there was no pop-off valve in the air box) In the thread above I contemplated replacing it myself but I just about to start a new job that would have big time demands so I decided to take it to a local and reputable shop, one that has been around for decades. I had the car flat bedded there on May 3rd along with a bunch of parts including:

* 911 110 904 00 - airbox
* 930 110 197 12 - intake manifold gaskets (6)
* 930 110 885 00 - intake sleeves (6)
* 999 701 423 40 M213 - injector O-ring (6)
* 911 110 886 03 OEM - insert sleeve for fuel injector (6)
* 999 701 446 40 M17 - injector sleeve O-ring (6)
* 999 701 210 4A - cold start injector O-ring (1)
* 999 701 395 50 - cold start injector spacer O-ring (1)
* 999 701 124 40 M17 - throttle body O-ring (1)
* 911 110 394 02 M30 - coffin gasket for sensor plate housing to airbox
and a pop-off valve

I asked them to let me know if anything else should be addressed as this was the first time the car was being looked at by a pro since I've owned it (both in 2008).

A week later, the shop called to check in. They found that the air box had been replaced at some point before I owned it and had loctited the nuts on the intakes. And the intakes were coated with a lot of carbon deposits. [sidebar: the car was running very well for the last few years and I had installed an AFR gauge years ago to keep an eye on AFR and it has never run exceeding rich]

At this point they adjusted valves, did a compression test (I don't have the numbers but it was fine. Engine has 191K miles on it). And did a lot of the other replacement parts on the list and the typical triangle of doom parts and installed the pop-off valve. He also replaced the distributor cap and rotor. Several weeks later they called and had installed the air box and had things back together and were finishing up tuning it.

And that's where this story starts...
On 6/17 I went to pick the car up and was told that it wasn't running as well as it should but that I should put 100+ miles on it with some good gas (remember, it had been sitting over the winter and I had not put gas in it yet this year). Driving home was a nightmare with lots of back fires - both exhaust and in the air box, I could hear the pop-off valve working. It was also at this point that I noticed my AFR was read "---" (this is an AEM gauge and 3 -es typically means out of range too lean. The next day I decided to plow through a 100 mile drive and was able to do that with some minor back firing, especially when decelerating. But it was not a pleasant drive. The shop agreed to come and pick the car up on Sunday (May 19th), which the did.

The car was in the shop from then until last Friday - October 4th - and still was not running well. But I wanted to get my car back and go through it myself. When I picked it up, they told me that they had replaced the OEM O2 sensor and noticed that when it was disconnected, the AFR gauge worked. (I have not verified this myself). They thought maybe the WUR was faulty but after testing, it turned out ok - but I did not get the test data. The car would cold and hot start "fine" but unless I give it gas immediately after starting, the RPMs drop and it dies. When cold: giving it gas and it won't idle below ~2000 rpm. Keeping it above 2000ish RPM keeps it running but it feels rough. I had some back fires on the drive home (15miles) and multiple stalls when stopping at lights and signs, but it always started right back up as long as I fed it gas as soon as it started.

I recalled that I may have spliced the power and ground wires for the AFR under the passenger seat on one of the relays. I took the seat out last Saturday but found that I had maybe spliced the wires there but had rewired at some time in the past.

So today (a week later), I started the process of going through the CIS system to try to resurrect my baby. It has been almost 10 months since I've really driven it so I've forgotten some of the basic things like "does the fuel pump come on when you turn the key to run" and "when do you hear the FV".

So let me start with the basics, I started by doing a fuel pressure test. Here is my data in the Pelican-approved format:

1. Year of engine: 1983
2. US or RoW (Rest of World): US
3. WUR model number: 0 438 140 090
4. Ambient temperature at time of test (in degrees C): 19.4°C
5. WUR Resistance (in Ohms): 25Ω
6. System Pressure (in bars): 4.8 bar
7. Cold Control Pressure (in bars): 2.25 bar
8. Warm Control Pressure (in bars): 3.5 bar
9. Time delta for Cold -> Warm Control Pressure: 3 min
10. Residual Pressure @ 5 min (in bars): 2.25 bar
11. Residual Pressure @ 15 min (in bars): 1.7 bar
12. Residual Pressure @ 30 min (in bars): 1.5 bar
13. Residual Pressure @ 60 min (in bars): 1.5 bar

I had taken the heater fan and large duct out to make some room and I noticed that one of the "CIS connectors" - the green one, was not connected. Green had 2 brown wires, so it is verified to be the AFS switch connector. I plugged that back in. But that did not make any difference in running. I then did a smoke test with a homemade smoke tester and it seems to be very tight, no leaks that I could find anywhere. The shop had replaced the rotten old lines.

Now I need help trying to figure this out. It bothers me that it cold and warm starts with a single key click (no cranking required) but needs gas to keep running. And it runs rough.

One of the few things in the CIS system that I don't have experience with is the FV. I plan to test the relay under the passenger seat - I had put my hand on it when I turned the car on and did not feel the relay activate. Normally you can feel these types of relays. This relay feeds power to the ECU and to the FV. When I turn the key to "run" there is no sound. I don't recall if I should hear the fuel pump and FV in the run position, I seem to recall that the fuel pump did run.

Anyway, I'm out to the garage to test that relay but wanted to write this up in the hopes it might trigger a memory!

I may be on to something. I tested for voltage on pins 87 and 87A on the FV Relay (aka OXS Relay) with the car running and there was none! I unplugged the relay and there was no change in startup and running behavior.

Fortunately, I have a replacement (correct) relay in my parts that I got years ago after reading a list of parts one should have on hand! Bosch 0-332-019-109

Now, things are very different - not right, but different I think in a better way.

The car started up and I did have to give it just a little gas. But then I could take my foot off the gas and it idled at 2000ish RPM and sound much stronger. Then after 30 seconds (or less) the idle speed started cropping up and I noticed that my AFR was showing in the 17s. I gave it some gas and the AFR came down to high 14s and crept back up and back to "---". Letting my foot off the gas to come back to idle resulted in a larger back fire in the air box - enough to blow the gasket out of the pop-off valve. I shut down and with the key completely off I heard this odd clicking sound from the engine bay. I made a recording of it. Here's the link: https://youtube.com/shorts/66hDgPFD93A?feature=share

Now, a few minutes later I just checked and it is not making any noise.

So, is it possible that the FV relay had died and the shop had not checked that and instead, tried to adjust the idle speed and mixture to richen it up? My understanding is that with lambda cars, the FV is constantly adding fuel to a lean mixture. So if there is no FV adding this fuel, perhaps the shop tried to compensate with the mixture?

In any event, where should I go from here?

I just went out to startup again and record things. Here is the video: https://youtube.com/shorts/-2tkhedWa_I?feature=share

As you can see, right after startup (and I did have to give it just a bit of gas) it idles at 1800RPM and then at about 30 seconds, it jumps up to 2900RPM and my AFR gauge starts to read in range.

So, I do think I'm heading down the right path. I believe the dead FV relay was the root of the issues that kept me and my car apart for all these months. Now I need to tune the mixture and set idle speed and set the lambda duty cycle. All stuff I've done and forgotten so I'll need to do a lot of reading. Any directions greatly appreciated!

I have no experience with late lambda systems, but since all your pressure test numbers look good, could you be having issue with the Aux Air Regulator or Aux Air Valve?

I don't think so Ed - the smoking gun was the inoperative FV relay. Although not impossible it is improbably that multiple components all failed at once! I think I'm just dealing with basic idle and mixture tuning at this point. That's the plan for tomorrow.

Lots of shops don't know about the FV system. When it fails, usually due to the relay, wiring at the relay, or a popped interior light fuse, the system goes way lean.They crank up the mixture adjustment to get it to idle better, but the engine still runs like crap.

I'm with John here, unfortunately even many 911 shops don't know anything about the FV system.

First - get a DMM with Duty cycle reading option.

The green plug behind the CIS is responsible for a proper working of the fuel pump safety circuit. If not connected, the fuel pump and therefore also the FV and WUR will be active when key position of ignition switch is on. So you can keep it unplugged for checking purposes, but after that workaround you should re connect it again.
--> So when you hear the fuel pump working, the FV should be buzzing, if not, ... check for proper voltage at the terminals of the plug of the FV. If voltage is ok, then check the FVs resistance, should be between 2 and 2.3 ohms. If not then replace FV for testing.

I did not read that a proper co setting has been done. So when FV is ok, unplug the OXS sensor and start the engine, with engine warm set – for testing purposes the – the CO to 1.2 %! Not 0.4-0.8. With this setting drive the engine and tell us if it runs better or even ok.

Then at idle, re connect the OXS sensor plug in the left engine compartment and check the Duty cycle at idle using the DMM -- explained here:
https://nineelevenheaven.wordpress.com/the-911-sc-3-0-engine-with-catalyst-and-lambda-control/
Read the part "The lambda control – display and check", there its explained how to connect the DMM in a proper way.
Then tell us what duty cycle is present at idle (with still the initial co setting of 1.2% as mentioned above)

Thanks John and Andrew. I’ve followed John for decades and I’ve studied Andrew’s site for hours!

As of my last post the FV is now indeed working but the idle speed is way high. I have not set the CO yet. I do have an oscilloscope and a DMM with duty cyle/dwell and have measured the duty cycle in the past. I also have an AFR gauge (AEM). I am not sure what the next steps should be given that my idle and mixture are likely way out of whack. I’m thinking I should see if tweaking the idle can get it down below 3000rpm when the engine is warm then set CO using the duty cycle method as described. I can verify that with the AFR too. I believe things are so out of range because they tried to tune with the FV and ECU inoperative due to the faulty relay.

Found this for you
<iframe width="560" height="315" src="https://www.youtube.com/embed/slCzVrrST2Q?si=n_VPCaJ8WpVh6SSJ" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>

Thanks for that video link! I've been working on my car's CIS for 16 years and thought I had found all of the good stuff on CIS! I learned a couple of things from this video for sure, not the least of which is the function and adjustment of the Deceleration Valve.

Wow, is working on the CIS on an engine stand MUCH easier! It is such a pain to get to those components in the car.

I had removed and verified proper functioning of the AAR back in 2016. (I keep a detailed log of everything I do and links to references on my car). I can check it again.

Today is rainy and 48° and my garage is unheated and the tail of my car is at the garage door side so working today is probably not going to happen unless the rain lets up some! I have a few other minor projects to finish like cleaning and lubricating the tracks on the passenger seat before reinstalling it, replacing the front hood shocks, and upgrading to H4 headlights. All stuff that was on my to-do list this year but wasn't able to get to since the car was in the shop from May to October :(

Based on all of the reading here, Andrew's page, stuff I saved from Jim's CIS page, etc I think the first step would be to adjust the mixture. This was probably the adjustment most out of whack because the shop tried to compensate for the non-functioning FV. Does that make sense? Given that I don't have a gas analyzer but do have a scope and in-dash AFR should I unplug my OEM O2 sensor and set the CO to 1.2 % as Andrew describes - but how do I target 1.2% with no gas analyzer? I am running E10 here in New England also.

yes – as it was described in my last post above ...
- With disconnected OCS Sensor (forces ECU to a duty cycle of 50%) set CO to 1.2%
- With engine warm re connect OXS sensor and read duty cycle with DMM


No, do the steps as mentioned above, as with following the steps above you can see how much duty cycle is needed to bring the combustion to result in lambda 1.
Also check if your ignition timing is set to correct 5° BTDC – with both vacuum hoses at the dizzy disconnected and ends of hoses closed/plugged to avoid false air. Dont use the reterd timing vacuum for now, .. this will be acrtivated at the very end if all other things are working well.

I guess that as well - a typical foolish way of "experts" trying to bypass a non working FV.

Setting the CO using the duty cycle method id only if all is working properly, which with your setup now it doesn't.
Do let a shop make the measurement with a calibrated CO analyzer. My clear recommendation.


Another question: How is your AFR gauge/controller connected? Do you have a separate connection soldered to the exhaust pipe? Or do you use a bracket at the end of the tail pipe? Or do you even provide a simulated narrowband signal from the AFR gauge controller to the ECU?

I chased keeping my CIS

tbh I regret trying to keep it

go ITB or pmo, rip the bandaid off and ditch that antiquated system

Thanks Andrew. So my challenge is going to be finding a gas analyzer. I can't drive the car and I am out in the country where there are no shops that can do this on my car.

I have a dedicated wideband O2 sensor installed in its own bung (what you are calling a connection) that is only connected to the AFR gauge. The car has the OEM narrowband O2 sensor for the lambda control.

Aztim - I've had minimal problems for 16 years and love this car. Thinking through this issue and timeline, I think what happened is that my FV relay had failed while the car sat over the winter and when I first started it back in late April on a cold, humid morning, the car backfired and blew my airbox. Part of that is shame on me for not having a pop-off valve installed. But, as it turns out, the PO had replaced AND repaired the airbox previously (maybe just repaired). I'm sure if I had installed the airbox myself I would have found the issue with the really working through the CIS troubleshooting steps like I did this week. I just didn't think I had the time to do an engine drop myself given my hectic schedule.

Ok, but if the Orig OX sensor is not connected to the ECU but to your separate AFR controller, then the ECU will switch to open loop control, resulting in a static 50% reading with a warm engine and a warm OX sensor.
This means that it with this it is not possible to measure a correct AFR or lambda value with your external AFR/controller.

Some more from the peanut gallery<iframe width="560" height="315" src="https://www.youtube.com/embed/K-OvjlkrgNo?si=UFC04zbXl_TpMyaY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" referrerpolicy="strict-origin-when-cross-origin" allowfullscreen></iframe>

Andrew, just to be clear - the original OX sensor is connected to the ECU. It always hqs been. A few years ago I simply installed an additional wideband OX upstream of the catalytic convertor that is dedicated to the AFR gauge that I installed below the dash. The original lambda system is exactly the way it came from the factory.

ok, thanks for clarifying, ... I was not sure if I understood that correctly.

No worries Andrew. Other than the fact that the AFR is not as precise as an exhaust gas analyzer, could I at least use it to get much closer to a proper mixture and then use the duty cycle method to dial it in?

As it is now the car starts up both cold and warm easily. If cold, it idles at about 1700 RPM and then after about 30 seconds it increases to 3000 RPM. If warm start, it goes to 3000 RPM idle almost immediately. At 3000 RPM my AFR gauge is showing a VERY lean condition - 16.0 AFR. I should note, when the car is idling at 1700 RPM on a cold start, the AFR gauge is not giving a proper reading, it shows three dashes "----" which is an "out of range" condition. I recorded the entire cold start sequence and show the AFR gauge as well in the video I posted: https://www.youtube.com/shorts/-2tkhedWa_I

It is only a minute long but shows pretty clearly what I am dealing with. And if anyone is interested, this is the AEM gauge I bought with the 4.9 LSU sensor. In the video, you can see I installed it in the console in my cabriolet with a 3D printed mount: https://www.aemelectronics.com/products/dashes_and_gauges/wideband_gauges/classic_wideband/parts/30-4110

My set up is similar to yours. 83 with full CIS with functional Lambda. If you are above 15C as you stated the only thing that changes at about the the 30 second mark is the O2 sensor(s) heat up enough to start doing their job. The - - - is displayed until the sensor is warm enough to function. Until then the FV is defaulted to 50%.
In your setup (and mine) this AEM sensor is a proxie for the factory O2 so we can assume that the factory O2 begins working at the same time your indicator turns on. So when your numbers pop up on the AEM your OE system is now controlling the FV.
The FV can make pretty large mixture (an thus idle) changes if CO is way off. Either your system is super rich and bogging (low idle) until the FV leans the mixture, or super lean (again, low idle) until the FV enriches the mixture and it surges to 3000.

I may have missed this, but at about the 2-3 minute mark (this from an overnight dead cold start) the WUR should be at full WCP and the AAR should be fully closed or nearly so. What happens to your idle if you wait for those two things to occur?

Regards

Thanks Funracer - that has not been the behavior in the past. I normally see the AFR gauge come to life immediately after it powers on - certainly within a few seconds. And, before I found the issue with the FV Relay, when it sort of idled (but required foot on gas pedal) the AFR never registered - even when I took the RPMs up to 5.5K while driving it home a week ago, it only showed the there dashes.

I have not allowed the car to idle at 3000 RPM for more than a minute or so, I can do this test today. It is still miserable cold and rainy here today but I can do this test this afternoon. I will also pay attention to when the AFR starts displaying, etc.

Currently - after replacing the FV relay - I don't have a low idle any more, I have a very high idle of about 1700RPM with what is apparently a very lean mixture (based on the AFR gauge display).

@Funracer, I recorded the entire cold start video for 7 minutes here: https://youtu.be/MI-dotNRNwA

some points;
Car sat overnight, no adjustments done since I replaced the FV relay on Saturday. It was 37°F (9°C) and it has been raining all morning so the humidity is high.

I tried to start several times and it would fire up and die. I finally had to give it just a little touch of the gas pedal and immediately backed off and it went into the 1700 RPM idle. This was at the 1:07 mark in the video.

My voice over timing remarks are a little out out of time by about a minute. But the entire elapsed time since startup was 7 minutes.

At 3:41 in the video, the RPMS went down about 100 RPM and you can hear it. This was about 2min 25sec since start up.

At 4:14 the RPMs started increasing. This was at 3min 7sec since startup.

At 4:50 the RPMs are at 2500RPM and the AFR gauge started to display 17.5 AFR.

At 5:08 the RPMS are at 2950RPM and the AFR is around 16 AFR. This is at 4 minutes from startup (I say 3 minutes in the video so I was off by a minute!) .

At 6:08 its at 3000RPM. This is 5 minutes from startup. AFR is around 15.5 at this point.

NOTE: the AFR seems to decrease as RPM goes up. This makes sense I think since what the engine is probably getting more gas, increasing the RPMs and lowering the AFR. (make sense?)

At 6:50 the speed has increased to about 3100RPM and the AFR is showing low 15s. This is about 5min 40sec from startup.

At 7:45 I start to give it gas to get the RPMs up to 4000. The AFR did decrease a bit as I gave it gas.

I then shut the engine down.

The weather is supposed to get up into the 60s here this week so I should be able to start to do some adjustments to the mixture.

Andrew, John and others have asked good questions and given good advice. The high idle after fully warmed up has me puzzled. I doubt that the FV could cause that high of idle RPM within its operating limits. If the AAR was hanging open, that could cause it. And one other dumb thing--the throttle is not closing all the way due to binding or maladjustment of the linkage.

So, have you checked that the throttle closes all the way? While it's idling at high RPM, go back and press down not he throttle arm to make sure it's all the way down.

On the bright side your engine sounds great!

Suggestions. Some may be have already been mentioned or you may have already looked at. Basic things but since someone else has been working on your car so you need to check it all.

What happens when you remove the oil fill cap when at high idle? Idle drop or go up?

What happens when you lift the air sensor plate 1mm at idle? Idle rise or stutter?

Did the shop loosen the throttle plate screw and change the factory throttle plate idle position?
Did they change the air sensor plate height?

First I would absolutely unplug the O2 sensor and leave it unplugged until you get a handle on what’s happening. Just to simplify things. FV will default to 65% below 15C then 50% above. Car may not run at 14.7 but who cares when you are troubleshooting a 4000 rpm idle. You can dial that in later.
Close the idle screw all the way clockwise, then open it CCW two full turns (2x360) just so you know where it is.
Since you car actually starts and runs I would then use your AFR gauge to set a warm mixture somewhere around 14.5 and see where your idle is then.
If its still way out of line, try a start with the CSV unplugged. Or start the car and when it gets up to 3000 rpm unplug the CSV. It might be stuck open adding extra fuel to the system.
Lastly at about the 4 minute mark your car goes from 3000 to 4000 rpm. Thats right when the WUR has reached WCP (leaner) and, as Pete mentioned, the AAR should close. Next time after shutdown pull the AAR tube and check that it is closed.

Regards

Having said all that, the lean readings on your AFR 15-17 and off scale high along with very high idle indicates too much air IMO. While its idling pop the throttle linkage socket off the throttle plate ball (left side throttle plate housing) and see if the throttle plate closes more. Are the throttle retract springs (2) in place? Maybe a hose clamp missing or not tightened on a vacuum line somewhere? Any openings on the throttle body uncovered? Decel valve hose attached or plugged on both ends? Popes hat ( I can never remember what its really called) fully on and clamps snug? Pop off leaking when warm?

I know you mentioned you did a smoke test. I have recently discovered that doing a smoke test on a hot engine can yield different results from smoke testing a cold engine.

Sorry not being very systematic but these are all easy things to check.

I only flew over this thread and didn't read everything in detail, also didn't read the history before yet.

But at first glance - I suspect the whole system now is "tuned" beyond anything by the workshop due to the lack of any knowledge about CIS / lambda CIS. Typical today unfortunately...
they enriched the mixture due to the missing amount of fuel from the lambda system...now the whole system is completely disordered.

On such a messed up CIS you basically have to check everything.

1.how many turns do you need to fully close the idle speed screw (how many turns CW, reset to the original setting afterwards)?
2. could you post a picture from the sensor plate on its resting position with sitting engine, so that we can see how its height is adjusted? (how sits it in the cone).
3. Pull the AAR (additional air regulator) and bench test it with a 12+ power source to see if it shuts as suspected

JoeEngineer has some good tips on how to bench test the CIS components: https://j.o.e-e.n.g.i.n.e.e.r.com/porsche-911-cis-subcomponents-and-testing/

You already know the KlassikATS YT channel by Kurt, but he's also got a complete video series about the 2.7 CIS 911 in which he explains almost everything you need to know about CIS. It helps a lot to get a better understanding of all parts from the CIS: https://www.youtube.com/playlist?list=PLkWFofpgz2OgF9FdliKnlzuY0pygqRkMj

Thomas

@ mhackney
As mentioned, ... first a "1.2%" resulting CO screw adjustment using an external analyzer as to be done, with engine warm and sensor unplugged so the ECU runs in open loop (50% Duty Cycle) mode. This is the starting point, ... all other things like I see in the video are "further" steps.

The only first thing I see/hear ist that (although now the relay works as you say) the mixture seems to be lean otherwise the idle would oscillate if it would be to rich. And on a too rich initial setting, the car would not start that easy on the second attempt without any following jerking.

Also as Thomas said, you will have to check everything, especially here the AAR unit as this seems to hold the idle very high even if its too lean – although ... an idle of 1.800 Rpm at cold temperatures in the 80s was normal during the beginning of the cold running phase / warmup.

But ... first do a proper CO setting first before doing any further attempts/steps.

Im with you here

Thank you all for your input and recommendations. I now have a plan, I just need the time (and the weather to cooperate) to implement it!

The only additional thing I could do yesterday was test the AAR and it is operating correctly.

The only challenge I have with Andrew's plan (I call "plan A") is not having access to an exhaust gas analyzer to set the CO. But I do think I can use the AFR gauge to get a lot closer than where it is now and once I have it running so I can drive it confidently, I can find a shop or place to borrow a gas analyzer to do a final tuning.

CO adjustment without first checking the sensor plate height and doing a basic CIS adjustment in conjunction makes no sense to me. As said, checking everything is key for a successful CIS troubleshooting. But my experience teached me to begin with the sensor plate height and basic CIS adjustment and only then to work all the issues with this setting that long until the engine runs as original again.

More about CIS basic adjustment:
https://forums.pelicanparts.com/porsche-911-technical-forum/1167170-cis-hard-cold-start-idle.html#post12323518

Thomas

In "this case" a CO adjustment should be done first, as said. As here the car was typically messed up by trying to adjust CO with a non working FV. In 90% of these cases it already helps very lot.

Don't you have a workshop near you that could do this for a small fee? A proper basic CO adjustment is essential for the first step. Without that you will never get your engine running the way it should. You should not adjust the initial setting using an AFR gauge, but with proper initial CO setting and with an engine with lambda control running use the duty cycle reading as its show's you if your mixture is on --> spot.

But ... I don't want to insist here. :-)

I honestly don't have a workshop near me that has a gas analyzer. My state (Massachusetts) does annual inspections that no longer require emission testing so all of the shops have deleted their analyzers. I've called several specialty shops and none want to touch a 80s Porsche 911. The shop that did the airbox install does have a gas analyzer and I could probably get time to use it but I am but comfortable driving the car there with a 3000RPM idle speed! I have the rest of the week before I'll have time to work on it so I am looking for other options. It's too bad that there aren't places that rent these like they rent other automotive tools around me.

Also, I did ask the shop if they adjusted the sensor plate and the claim they did not. I do believe them. I don't think they are bad, I think they haven't worked on many CIS cars in a long time and it is easy to forget the details - especially for the 80-83 series that have the lambda CIS like my car. The other work they did was done well.

ok, then lets proceed as follows: (sorry if something already has been mentioned or even done by yours above).

- Keep orig OX Sensor plug disconnected, so Open Loop (50% duty cycle) will be present at the ECU
- Unplug all hoses at the dizzy and close their ends using plug or similar, so no false air will enter the manifold

1. Start the engine
2. When engine is running at least for a while so that it isn't really cold, do check with DMM that the duty cycle is 50% and not 65%, means engine temp must be above 15°C.
3. Try lowering the the idle speed with the idle screw, if not do check if the ignition timing at idle is at proper 5° BTDC. If still idle is that high, could be a non closing AAR or an air leaking AAV.
4. Now with your AFR controller/Gauge running and displaying the mixture level do turn the CO screw clockwise till 14.7:1 is shown.
5. Now re connect the original OX sensor so the ECU switches into closed loop mode
6. Check now the resulting duty cycle, its should be still around 50%

- if you don't manage to get the idle speed below 1,000 rpm, then ...
1. get a vacuum gauge which is capable showing values till -1 bar (-100 kpa).
Do connect this vacuum gauge to the vacuum connection port on the rear side of the throttle housing. It's the one where the tempomat (cruise control) and the deceleration valve are connects to via the little hose T-connector. Its the green hose shown in here:
https://nineelevenheaven.wordpress.com/wp-content/uploads/2021/09/unterdruckanschlucc88sse-930.16-sc-911.jpg
This is the manifold vacuum, and here check if even at higher idle a significant vacuum drop is given (let's say below 40 kph), if yes continue with the next step.
2. if idle is still to high .... check for false air using a smoke test – (these ones are cheap at eBay, get one, do the test, and if not needed anymore you won't loose that much money if you sell it again).
3. if idle is still too high ... disconnect the deceleration valve on the very right side (the one with the small vacuum hose attached) and close the hoses ends where it was connected to, to see if the idle drops. The next step would be testing the AAV but that one is behind the engine on its right side, almost not possible to check without dropping the engine.

As your engine was running well before for 16 years, I don't think a de adjusted sensor plate is the issue, if it really has not been touched by the shop as they say.


And after this whole journey... do report.

I greatly appreciate the "plan" Andrew. I will follow it to the letter later this week - Saturday at the latest - and report back. I have all of the tools (including the vacuum gauge). Saturday is supposed to be 65°F / 18°C and sunny here so it will be a lot more enjoyable to work on my baby!

Ok, today's the day. It is 60°F (15°C) and climbing to 70° today.

Following Andrew's procedure:

Disconnected the OX sensor
Disconnected and plugged the two hoses from the dizzy
Connected my DMM (Fluke 107 which does duty cycle)

Then I started the engine. It was a little more difficult to start and did require just a bit of gas as soon as it started but then went up to 1900RPM or so to start to idle. At this point, the duty cycle was 65% and then as I heard and saw the RPMs start to drop to about 1600 RPM the duty cycle went to 50% and the engine died. I restarted (again with just a tweak of gas pedal after ignition) and the engine idled steady at 1600 RPM and the duty cycle was 50%. No reading (three dashes) on the AFR gauge. I let the car idle for a few minutes to get the engine hot.

So far so good.

Then I went to adjust the idle speed and discovered that it was COMPLETELY screwed all the way in (clockwise). If I turn idle speed adjust counterclockwise, the engine speeds up, so I turned it out to get the idle speed up to 2000 RPM. Still 3 dashes on the AFR.

At this point I got my 3mm wrench to adjust the CO screw and immediately dropped it behind the engine after my hand touched something hot and I flinched. The engine is too hot to explore with a mirror and magnet so I need to wait until it cools down a bit.

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At this point, I think I should check the timing and then move on to adjusting the CO.

Ha we have all been there.

Ok, I was able to retrieve my mixture tool but in the process of looking around with the mirror I found this loose connector. It is to the left side of the throttle and towards the firewall. I can't find where it connects and I don't recall seeing a single spade connector like this in any of my photos or research.

http://forums.pelicanparts.com/uploa...1729353784.jpg

any ideas what' this is?

As a datapoint, the Gunson GasTester (G4125) is kind of finicky, complicated to use, relatively expensive (especially considering the old-tech) and sloooow (long warmup time, slow response/measurement, long after-use purge).

That said, mine, used according to directions, provided CO2 readings that corresponded very closely to the figures from my wrench's 5-gas analyzer...

Ok, so I checked the timing with the idle screw completely screwed in - the way it was. Tweaking the dizzy counterclockwise brought the idle speed down. It appears that there was a lot of timing.

Unfortunately, my garage door faces due south and the sun is really bright and hot today and the engine was still quite hot. I "think" I set the timing at 5° BTCD at 1400 RPM.

The exhaust really smells lean to me too - more noticeable now that I am working near the tailpipe.

And the engine is quite hot - a combination of the direct sun and running. I can't really do anything else until it cools off. I closed the garage door to let things cool and will get back to work in a couple of hours.

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Given how far out of whack the idle screw (completely closed CW) and timing were, I suspect the CO mixture is really out of whack too. Maybe it makes sense to check and do a rough base set on the mixture as described at the 45:30 mark in this video https://www.youtube.com/watch?v=K-OvjlkrgNo (Classic Automotive Training).

That seems easy enough to do and at least I will know I am within range - and I'll probably get a good idea on how lean it was set.

I need to let the engine cool before I can proceed but I have my fuel pump relay bypass installed and ready to go.

Ok, cooled off enough to get back at it.

Firstly, I checked the mixture rough base set as per the video above. Surprisingly, it seemed pretty much as shown in the video with no adjustments.

So I started the car up and was able to set and verify the timing at 5° BFTDC. Idle is about 2200RPM (I had also set the idle adjust screw to 2 full turns CCW from fully screwed in (as per baseline setting). So I started turning the idle screw in (CW) to bring down the idle speed. Got down to about 1700 RPM but again, almost completely screwed in.

So, I did the air sensor plate lift test. Results:

lifting the plate, the RPMs increased
pulling the plate down, the RPMs decreased

So this tells me that it wants to be richened. It should drop RPMs a little when lifted and when pulled down.

So I thought, while I'm thinking about it, let's see what happens when I remove the oil filler cap to see if RPMs drop. I removed the cap and the idle speed started dropping and then the engine stalled.

At this point, I'm ready to adjust the CO screw clockwise to richen (Andrew's step 4) but the sun heat and engine heat are a little too much (we are up to 75°F now with bright shining sun).

What are the limits of the CO adjustment screw? I don't want to go too far, does it bottom out when screwed all the way clockwise?

In addition to the disconnected spade connection I mentioned above, I also found this 2 wire connector on the left side just above and behind the WUR. brown wire and yellow with black stripe. I don't see where this might plug either and I don't recall it from working in the past. One note: I did do an AC delete on this car.

EDIT: I REMEMBER bow - this is the heater motor connector! Doh!

http://forums.pelicanparts.com/uploa...1729364583.jpg