Okay, today was a complete failure to find the problem. Steps taken today:

- Filled the car up with oil

- Replaced the ignition wires (no change)

- Replaced the coil (no change)

- Replaced the DME relay

- Emptied all the gas out and refilled it with fresh gas (no change)

- Checked the fuel injection wire harness *completely*:
- Resistance of each fuel injector coil, measured at the injector plug
1- 2.5 ohm
2- 2.5 ohm
3- 2.5 ohm
4- 2.5 ohm
5- 2.5 ohm
6- 2.5 ohm

- Resistance of each injector coil as measured through the harness to pin 14, 15 and 87 on the DME relay
1- 3.2 ohm
2- 3.0 ohm
3- 3.0 ohm
4- 3.8 ohm
5- 9.1 ohm
6- 11.6 ohm

- Harness resistance to pin 87 from injector plug
1- 0.4 ohm
2- 0.4 ohm
3- 0.3 ohm
4- 0.6 ohm
5- 1.0 ohm
6- 2.0 ohm

- Harness resistance to pin 14/15 from injector plug
1- 0.5 ohm
2- 0.5 ohm
3- 0.5 ohm
4- 1.0 ohm
5- 2.0 ohm
6- 3.8 ohm

- Injector plug harness resistance to 4-pronged plug (left / right pins in connector)
1- 0.5 ohm / 0.5 ohm
2- 0.5 ohm / 0.3 ohm
3- 0.5 ohm / 0.3 ohm
4- 0.1 ohm / 0.8 ohm
5- 1.8 ohm / 1.0 ohm
6- 1.3 ohm / 1.3 ohm

- Four-pronged plug to ECU & DME relay
pin 1 -> 87 DME Relay - 1.9 ohm
pin 2 -> 87 DME Relay - 1.4 ohm
pin 5 -> 14 DME Connector - 0.5 ohm
pin 6 -> 87 DME Connector - 0.6 ohm

- After cleaning with isopropyl alcohol, placed a 9V batter on pins 87 of DME relay and DME connector pins 14 and 15. Measured the voltage (reference voltage at battery of 9.43 volts)
1- 9.43 volts
2- 9.43 volts
3- 9.43 volts
4- 9.43 volts
5- 9.43 volts
6- 9.43 volts

Conclusion? There was a small increase in resistance in the harness on the side of the motor containing cylinders 4-6, but the voltage drop test didn't seem to indicate that it had any effect. This was with very little current, of course, but my gut is that that these values are not enough to cause issues. Still, some clues seem to point to there being an issue on this side of the engine, and perhaps also with respect to cylinder number 6 (where the resistance in the harness seems to be highest). I still don't think that it's high enough to be causing problems. The connectors are available, I can create a new harness, if even to just test to see if it's an issue.

So, I'm beginning to think that I my initial diagnosis of the issue was incorrect. I think the car was missing all along, and that because the idle was initially set to be around 1,100, I didn't recognize that the car was missing when running and/or starting up. Now, it starts missing at startup, but you have to listen very carefully for it. I think lowering the idle down a bit made it much more obvious? Maybe. I can't recall now exactly how it was running when we first put it back on the road in February. I honestly don't remember it running / idling really terribly - it does feel like it's gotten worse.

When I did the compression check on the engine, I pulled all of the plugs that had about an hour's worth of "idling time" on them (installed new ones today to see what they look like next time I pull them). For the most part, they did not look very good. They actually looked like they had bad fuel gummed up on them (hence why I replaced the fuel). There's no smoke coming out of the tailpipe (neither white or black), although today, there was a small, slight wisp of white smoke for one second on start up - nothing remotely significant.

I'll post the pics of the plugs - the worst one is #6, but they all have brown discoloration on them. Again, these have about an hour on them total, in this poor running engine.


Next possible steps:

- Replace cylinder head temp sensor and/or use paperclip to short it out to test
- Perform leak down test (warm car, if possible)
- Pull injectors one-by-one very carefully and monitor to see if the (seemingly random) misfire is associated with one of the cylinders in particular (already did this, but will do it again)
- Start the car from complete cold and check with the thermal camera / thermometer 30 seconds after starting for header temps. If there is a subtle misfire, then one of the cylinder temps will be slightly less - letting the car run for a length of time seems to merge the temps together.


Any suggestions would be helpful, I'm really scrapping the bottom of the barrel for ideas.

-Wayne

http://forums.pelicanparts.com/uploa...1589181184.jpg

http://forums.pelicanparts.com/uploa...1589181184.jpg

http://forums.pelicanparts.com/uploa...1589181184.jpg

http://forums.pelicanparts.com/uploa...1589181184.jpg

http://forums.pelicanparts.com/uploa...1589181184.jpg

More photos. #6 is the first one, then 1,2,3,4,5

http://forums.pelicanparts.com/uploa...1589181303.jpg

http://forums.pelicanparts.com/uploa...1589181303.jpg

http://forums.pelicanparts.com/uploa...1589181303.jpg

http://forums.pelicanparts.com/uploa...1589181303.jpg

http://forums.pelicanparts.com/uploa...1589181303.jpg

http://forums.pelicanparts.com/uploa...1589181303.jpg

Some better photos. #6 is the 2nd one below. I do not think that the base ring should look like it's covered with bad, gummy fuel. If you touch the base ring, it's sticky / wet.

http://forums.pelicanparts.com/uploa...1589181423.jpg

http://forums.pelicanparts.com/uploa...1589181423.jpg

http://forums.pelicanparts.com/uploa...1589181423.jpg

http://forums.pelicanparts.com/uploa...1589181423.jpg

http://forums.pelicanparts.com/uploa...1589181423.jpg

I thought that perhaps the fuel injection cleaning shop made a mistake on the injectors, but I checked the flow rates and they seem okay. Here's a neat site that contains all of the resistance values and flow rates for the various injectors:

https://www.injectorrx.com/fuel-injector-cleaning-and-flow-testing-service/fuel-injectors/fuel-injector-data/bosch-fuel-injectors/

Another one: https://www.robietherobot.com/storm/fuelinjectorguide2.htm

http://forums.pelicanparts.com/uploa...1589182877.JPG

Here's the output from the shop again:

http://forums.pelicanparts.com/uploa...1588709576.JPG

Then again, I swapped around injectors and it didn't seem to make any difference whatsoever...

-Wayne

I also took several photos with the FLIR infrared camera. Hmm, I didn't see these numbers until I just uploaded them here. The temps on #6 appear to be a little bit lower, but that *could* be caused by header design. I have no "pre-problem" data on what they should be under normal operation.

When the car misses, I do hear a very light / faint "slapping noise" on the left side of the engine from within the engine bay, and today, I also heard it quite a bit when I had my ear near the left rear wheel. It almost sounded like it was coming from inside the oil tank.

Hmm. So, we seem to have the following - higher resistance values in the harness for injectors 5 and 6, and lower exhaust temps on #6. That is just a bit way too coincidental for me.

Still, the compression check on #6 came back very strong:

http://forums.pelicanparts.com/uploa...1589184072.jpg

I wonder what the leakdown would say...

Tomorrow I'll be getting the replacement / test connectors for the injector harness, and I can quickly build a test harness to see if this problem goes away.

http://forums.pelicanparts.com/uploa...1589185050.JPG

-Wayne

Cylinder #1:
http://forums.pelicanparts.com/uploa...1589183295.jpg


Cylinder #2:
http://forums.pelicanparts.com/uploa...1589183295.jpg


Cylinder #3:
http://forums.pelicanparts.com/uploa...1589183295.jpg


Cylinder #4:
http://forums.pelicanparts.com/uploa...1589183295.jpg


Cylinder #5:
http://forums.pelicanparts.com/uploa...1589183295.jpg


Cylinder #6:
http://forums.pelicanparts.com/uploa...1589183295.jpg

A+ for perseverance. i gotta say.

If you have an automotive stethoscope, you can hear each injector clicking when it's running. If it's not firing, no clicking. If it's even partially plugged, it'll go "thud thud thud" instead of "tink tink tink." If it's intermittently missing and you think it's an injector harness problem, try the stethoscope trick. Play with it until you get a sense of what you're hearing.

Those old cars were sometimes tough to diagnose. The newer cars point you in the right direction with the trouble codes they give.

Not always!!! A good example is a mis-fire code.

Injectors 5/6 aren't being driven properly thru the harness!

Holy cow! Would you believe that a replacement harness (that I made this afternoon) did *not* work!?! After all that, I was quite sure that would work. To recap, we had the following:

- Lower temps on #6
- Higher resistance on the #6 injector
- Spark plug on #6 was looking poor

I mean, what more could you ask for. Once again (it's now going on 25+ year), this car is kicking my ass. Just to recap, this is the car that I bought several years prior to me starting Pelican (bought the car in 1995, started Pelican in 1997). I've probably spent 1,500 hours working on this thing over the year (including tracking it down when it was stolen). NOT WORKING YET!!!

Okay, so the replacement harness had no effect. It does not appear to be the harness. However, I did unplug each injector and slowly / carefully listened for the miss. It's definitely coming from cylinder #6. I managed to do a leakdown test on #6 tonight (right before my leakdown tester hose sprung a leak), and #6 is showing about 3% leak down - no problems there.

I also spent a chunk of time looking at the engine with the timing light today. I did not see a single variation or blip in the timing lamp frequency / strobe. Nothing, nada - looks perfect. This does not appear to be an ignition problem.

I took a look at the exhaust temps again. Lower temps on #6 and lower temps on #3.

So, I did an interesting experiment today. I unplugged all three injectors from 4-6 and ran the car on only 3 cylinders (1-3). The car ran and didn't skip, miss or stall (didn't run well, but ran consistently). Then I plugged the other three back in and the car started to randomly miss. Then I unplugged 1-3 and ran the car on only 4-6. It too ran fine with no missing. Plugging them all back together results in a miss (looks like the miss is coming from #6). I have a video of this very odd behavior.

Cylinder number six was recording lower temps today, but then when I started unplugging injectors, it started to not miss and record normal exhaust temps. Odd. I also saw something similar with cylinder #3, although less pronounced.

So, we have the motor running consistently on 4-6 only, and also on 1-3 only, but 1-6 make it miss. How confusing is that? The curious thing is that the fuel dampener is located *right* next to cylinder number six. The pressure regulator is located next to #3 (which also seems to be recording lower temps).

Tomorrow I will swap out the injector on #6 with the injector on #1 and see if a problem follows the injector or stays with #6. It very well could be a bad injector, *or* it could be something with the fuel pressure regulator and/or the fuel dampener. Either way, this problem has been *very* difficult to track down. I thought for sure it was the injector harness, but that doesn't appear to be the case. I made an alternative harness for both #5 and #6 and wired them directly into the breaker box ===> NO CHANGE.

So, I have a video, where I unplug #1-3 and then plug them back in and then unplug 4-6 and then plug them back in. The engine runs consistently on 3 cylinders, but when plugging in all six, it misses and runs poorly. What does this mean? Who the heck knows, but now my theory is the pressure regulator and/or the pressure dampener. Either that, or a bad injector (we'll figure that out when we swap out injector #6 with #1 tomorrow). My gut is that the problem will stay with cylinder #6, as I just had all of the injectors cleaned and tested okay.

Video (poorly shot) of the car with me unplugging a whole side of injectors and then plugging them in on the other side:

<iframe width="560" height="315" src="https://www.youtube.com/embed/BDwxXzAKngQ" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

Timeline:

- Start -> Injectors 1-3 are unplugged, car runs on 3 cylinders, but evenly.
- Then I go an plug them in, car runs poorly on 6 cylinders (with missing) - Video at 0:25 - 0:46
- Then I go and unplug 4-6 injectors, car runs on 3 cylinders, but evenly. - Video at 1 min - 1:25
- Then I go and plug back in 4-6 injectors -> car runs poorly on 6 cylinders - Video at 1:50 - 2:10
- Then I go and unplug injectors 1-3 again -> car runs on 3 cylinders, but evenly. - Video at 2:40
- Then I go and plug everything back in again, car runs poorly - Video at 3:00

Bottomline, the car doesn't miss on 1-3 only, and doesn't miss on 4-6 only. But when all six are plugged in, the car runs and misses. What could be causing this? At this point, there's only one thing I can think of - the pressure regulator and the fuel dampener. These would appear to be the only things that could cause this behavior?

Summary:
- I believe that the problem with this missing is focused around cylinder #6
- I do not believe it's caused by an ignition issue
- It does not appear to be a wiring harness issue
- It's probably not a mechanical issue (compression test and leakdown on this cylinder looked good)

Could be a fuel injector issue or a fuel supply issue. We'll swap injectors tomorrow, and I'll see if I can borrow a fuel pressure regulator and a dampener from someone. Or perhaps there is some off-the-shelf BMW or VW part that may be relatively cheap that I can swap in and use.

Thoughts?

-Wayne

-Wayne

I may have missed it, but have you checked fuel volume delivery? Should be something like 850 ml in thirty seconds.

Again:

Injectors 5/6 now indicate the same resistance as 1-4, right? If not, why not?
If OK, switch injectors 3 & 6.

"baby bottle" test. to determine flow/pattern out of injectors? http://forums.pelicanparts.com/porsche-911-technical-forum/954591-here-i-go-testing-my-refreshed-1983-lambda-cis.html

Have you verified fuel flow volume and/or cleaned the supply line screen in the bottom of the tank?

Have you checked to make sure the supply and return lines are not kinked? Is this using the stock 914 fuel pump mounting location? Does yours have the "window" on the DS of the bulkhead to mount the fuel pump? Is this the stock fuel tank?

I used to have issues with the return loop of the pressure side of the pump getting kinked under the fuel tank when the pump was removed/replaced. careful hose routing is required.

It is possible for the engine to run normally for a short period of time until the fuel pump can not deliver enough fuel to support the overall requirements. Restricted fuel screen would also cause this issue.

You might continue scrapping the bottom until you realize the problem is not fuel related but an ignition problem. Plugs do not look that way unless they are missfiring and that points to an ignition problem. Modern cars eliminated that problem when they eliminated the distributor/ignition cables for that very reason.


Cheers,
Joe
87 Carrera that had lots of problems with plugs looking like that until I concentrated my efforts on ignition!

Did the 5/6 injector harness resistances come down to match the rest when you tried your test harness?
Have you had the injector harness off to inspect? I found mine to have worn through the vinyl sleeving and some of the injector wires' insulation when i had my engine apart for rebuild a few years ago. I suspect it could have been shorting to the fuel rail.

We emptied the tank and refreshed the fuel on Sunday. While I did not exactly measure the fuel flow, we were able to fill a 5-gallon gas can in about 3-4 minutes. This was out of the "fuel pressure test port", so there doesn't appear to be a clog or problem with volumetric flow?

-Wayne

Hmm, so emptying the tank (which is what we did) would indeed presumably bypass the return line. But that might show problems across the board - not just on cylinder number six?

-Wayne

Thanks Joe. At this time we've replaced 100% of the ignition system:

- Plugs
- Wires
- Cap
- Rotor
- Coil
- ECU (test unit loaned to us by Steve W.)

I guess I haven't replaced the distributor, *but* I took the timing light yesterday and checked (for about 2 min) cylinder number one, and cylinder number two. They were spot-on. If there were an ignition problem, I'm not seeing any clues to that anywhere, and I wouldn't know where to look next either?

-Wayne

So, I missed uploading a video that gives another data point. I noticed that the fuel pressure gauge yesterday started vibrating. I hadn't seen that before, and this seems to hint at the fuel pressure damper and/or pressure regulator not performing their respective tasks?

Some people have said that he damper is used to insulate the injectors from pulses contained in the pump, and some have claimed it is used to even out the pulses that would emanate from the fuel injectors. I have not seen a BOSCH document that definitively indicates the purpose of the fuel damper - I'll have to keep hunting for it...

<iframe width="560" height="315" src="https://www.youtube.com/embed/N_Btf97Idr4" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

-Wayne

"..I did not build this car, and when it arrived at my shop (with the 3.2 installed) it never ran correctly..."

I suspect the firing order was probably screwed up from the start. Can I assume that was checked?

Sorry, but I just hate assuming anything.


Cheers,
Joe

Thanks, that has been checked multiple times, and I just installed new plug wires so that is definitely correct now.

-Wayne

subscribed.... (still reeling from all the information, it's quite a read)

Maybe time for a summary post that puts all observations into one place. Sometimes organizing thoughts like that will give you and others a clue.

No way it could have a sucked/blown intake gasket is there? the spacers can crack too.
http://forums.pelicanparts.com/uploa...1589317535.JPG

Please, more videos! You're very close to finding the problem, right?

John - that should create a huge leak that would have shown up with the smoke test presumably? Also, these were supposedly replaced (although in 2008 - maybe less than 200-300 miles on the car since then).

Ingo - I am planning on summarizing, perhaps into a single post / word doc - if this disaster continues on!

Today's thoughts (haven't worked on it yet):

- I have a new pressure regulator coming, heading out to pick that up shortly.

- I have my fuel pressure gauge hooked up to the test rail and have been running it with it there. I had a long length of hose that I used just because I had it on hand. I'm wondering if the fuel hose itself could be acting as a rubber spring on the fuel pressure and the test equipment could actually be causing problems? I will disconnect today to see.

- Robert at DC Auto is hunting for a pressure damper to loan to me. There's also a few on eBay, but who knows if they are any good (they presumably have to hold vacuum. Speaking of that, I tested the pressure using vacuum from the manifold, but I never "sucked" on the units to make sure that they were holding vacuum on their own. I will do that today.

- As mentioned previously, I will swap injector #6 with #1 and see if the problem stays with cylinder number six, or moves to number 1. Wouldn't it be nice if this were just a problem with a single injector?

- I will check the resistance of the injectors with my new harness - I didn't do that yesterday and some here called me out on it :). Agreed, the new harness should be an improvement over the old one and should match the other injectors.

The oddest thing about all of this is the fact that the engine seemed to run okay on three cylinders on the left, and then three cylinders on the right, but when put together, it starts missing. This just plain doesn't make any sense, unless there is something odd or wrong with the fuel rail and/or hoses, and/or fuel pressure regulator / damper. I had a thought that one of the fuel circulation hoses might be getting clogged in the engine compartment, but my gut is that not the case (due to the fuel flow I saw into the gas can on Sunday).

-Wayne

I don't think that your full poor running engine is specifically related to #6. Something is acting on the engine to make it globally run poor.

I don't think its ignition or ECU related given your suite of tests. (very thorough BTW makes me want to build a breakout box)

Does fuel pump get hot after running for a few minutes?

Here are the plugs from yesterday (maybe an hour of "idling time" on them), for cylinders 5 and 6. Cylinder 6 seemed to have the problem as far as I could tell, but these plugs look remarkably similar.

Cylinder #6 is the plug on the top.

http://forums.pelicanparts.com/uploa...1589319424.jpg
http://forums.pelicanparts.com/uploa...1589319424.jpg
http://forums.pelicanparts.com/uploa...1589319424.jpg

-Wayne

does it look like unburned fuel on those spark plugs?

Ivan

Wayne,

Have you ever closed on the reported discrepancy between the WB O2 sensor and the regular O2 sensor used by the DME. I thought I saw something a couple of pages back in that regard. From my simple observations (my DME test stand simulating an ALL-LEAN or ALL-RICH O2 signal) I can see how the mixture (inj pulse duration) gradually changes at a given RPM/load/sensor snapshot in response to the simulated condition.

Given that the 914 probably doesn't have the stock 3.2 exhaust layout maybe the NB O2 sensor isn't seeing a representative gas mix (position, exhaust leak, etc). Your core problem statement seems to be "poor idle after warm-up". Let's assume it is a wrong mixture at idle. Mixture is impacted by the following:

- setting of air bypass screw in AFM (defines how much air has to pass through the barn door and sets it's position at idle, independent of ICV position)
- any modifications someone might have made to the AFM spring tension
- O2 sensor age, location, dynamics, noise on signal line, etc.
- functioning CHT, IAT and idle contact
- Any non-zero amount of 'other' unmetered air (aka leaks in intake). Sounds like you tested that

A quick test with the break-out box could be to jam the O2 sensor response to full-rich or full-lean and see how the idle behaves after all is warmed up. A simple 1.5 V battery connected to the signal or the signal grounded accomplishes that. Just a thought.

Ingo

I can check (I think). The fuel pump is located underneath the car in the front. I was thinking that the location of the fuel pump might have something to do with all of this, but the fuel pressures checked out, so that possibility was and still remains remote in my opinion? Still, it could be an issue.

As for something globally? That's what I thought originally. Then I saw that #6 was:
1) running cooler according to the FLIR thermal camera,
2) had higher resistance on the injection harness,
3) had the dirtiest spark plug,
4) seemingly causing the miss to go away when the #6 injector was unplugged

However, saying all that, my gut is that there is something indeed globally wrong, which may be manifesting itself in issues on #6. The miss is seemingly random. I can stop the miss (I believe) by unplugging the injectors on the opposite side. If I look at the injector pulses in the oscilloscope, each time they look very consistent in frequency (if not voltage amplitude).

I'm going to make those changes I put in the previous post and then see what happens...

-Wayne

The injectors are fired in batches, as 1-3 and 4-6 are wired in parallel, so that does make some sense.

Hmm... some suggestions that you might've already tried:

Has the air flow meter show signs of having been opened?
Have you checked to see if in a dark garage you have the same spark intensity (bright blue, not orange) as on other cylinders?
Sprayed diluted saltwater (helps conductivity) while engine is running to force any ignition voltage loss?
Smoke tested the intake system?
Does your 3.2 have the correct oil trap screen in the vent line back to intake from oil tank? Plugs look oily to me...

All six injectors are wired in parallel to each other and fire at the same time. The fact that the DME has two outputs (one for the left bank and one for the right bank) throws people. Internally both pins are connected to each other and driven by the single injector stage.

The injector driver circuitry "sees" 6 injectors wired parallel to each other. Each injector's DC resistance is ~2.6 Ohm. The effective resistance of all six in parallel is 1/Rtot = 1/R1+1R2+....+1/R6 - it comes out to about 0.43Ohm. This is not a trivial matter and hence the peak&hold PWM driver scheme.

One bad injector (internal short) will inhibit everything. A bad injector (internal open) will just not participate but leave the other five happly fire away....

The waveform of the injector voltage is simply a result of the hold-stage in current feedback. Depending on the connected load (# of injectors) the duty cycle will vary a bit.

There is an initial opening pulse of about 400us (peak phase) that is to shock the injectors open and then the driver switches to hold mode where PWM waveform is used to maintain a set reduced current in current feedback mode. At the end when the injectors close you get an inductive dump spike. This is when the magnetic field breaks down and it is addressed in a dump stage to prevent damage to the main driver output.

The frequency of the hold phase is set via an external RC network and fix. Amplitude is near 12V VBat and duty cycle and end pulse dependent on # of injectors.

Okay, so the results of today (NO CHANGE).

Here's what I did:

- Swapped injector 1 with injector 6

- Removed the fuel test gauge and reinstalled the plug

- Checked the resistance of the injectors (through harness using 87 and pin 14 or 15). This has improved on injectors 5 and 6. Not completely surprising as I cleaned all the contacts with either isopropyl alcohol, and/or some q-tips or sand paper, etc.:
1- 3.1 ohm
2- 3.0 ohm
3- 2.9 ohm
4- 3.3 ohm
5- 3.3 ohm
6- 3.2 ohm

- I took a closer look at the fuel pump after cleaning the injectors. It's occasionally making some noise, but nearly all fuel pumps seem to make some random noises. Sometimes it will go 30+ seconds without any noise. The fuel level is now slightly low (I added some more clean fuel prior to starting it up today), so this may be a clue, or may be nothing. It may also be circulating some of the bubbles out of the system from when it was cracked open swapping the injectors. Not sure yet, I will check it again tomorrow for any noise. Here's a video of the noise:

<iframe width="560" height="315" src="https://www.youtube.com/embed/kPbKR-a7jxc" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>





- I tested the pressure regulator and pressure damper to see if they held vacuum. I don't have my vacuum tester here at home, so I used the "grassroots" approach:

<iframe width="560" height="315" src="https://www.youtube.com/embed/a0OvfU5uK7M" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>





Started the car after this -> no changes. But, again, it seems to run much better when stone cold:

<iframe width="560" height="315" src="https://www.youtube.com/embed/-w6H5FhIGaU" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>




Running on 1-3 runs consistently, poor running on all six, and then fine on 4-6. Interesting, here's a video with timeline:

1- Started car with it running on 1-2-3 only (4-6 injectors are unplugged, O2 sensor unplugged)

2- Replugged in 4-5-6, runs and stumbles

3- Unplugged 1-2-3, runs fairly consistently and evenly on the three cylinders 4-5-6

<iframe width="560" height="315" src="https://www.youtube.com/embed/h85DItt9zRA" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>




Okay, so here's a weird video:

1- Running on all six cylinders (poorly). AFR shows it's running lean on 1-2-3 (the O2 sensor port is on this side)

2- Unplug 4-5-6, runs consistently on 1-2-3, AFR shows it's running much less lean (near 14.8-15.0, which is close to 14.7 - normal/ideal).

3- Then replug in 4-5-6, and the AFR goes from about 1.47 to 16+ (goes very lean on 1-2-3)

<iframe width="560" height="315" src="https://www.youtube.com/embed/EMCpmy8ew_E" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>




Finally, here is the "Ingo Test", where I used a 1.5-volt C-battery to simulate rich and/or lean conditions:

1- Running on all six cylinders, running very lean (17 AFR), voltmeter shows reference voltage of 4.9 from ECU.

2- Added in the 1.5 battery to simulate a rich mixture, which means the car will try to lean itself out (which happens as the car goes to 23+ - how is that even still running?).

3- Removed battery (back to reference voltage of 4.9 volts), AFR around 17

4- Grounded out O2 sensor (which simulates a lean mixture) - car went richer, 14-15 and ran better, but then went lean again randomly (at around 1:21)

<iframe width="560" height="315" src="https://www.youtube.com/embed/sAlEYbNMt0c" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>




Finally, I swapped out the sport muffler, just in case it was causing some weird reversions, etc. Didn't help. Here's the video from that.

Starts, sputters, etc, but now it appears to be running rich, and then goes lean and starts to sputter. Higher rpm revs are fine, but the engine still sputters and misses during those too. There's also an air whine / whistle that can be heard - the car had a big whistle last few times I drove it. I thought it was related to the revamped boots and the air filter too, but who knows now - maybe it has something to do with something.

<iframe width="560" height="315" src="https://www.youtube.com/embed/rKnOlH4cVHs" frameborder="0" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>

I haven't had a chance to really think about all of this tonight, got some other family stuff going on right now that is distracting me from the really important 914 stuff!

-Wayne

Air flow meter - haven't taken it off, but the output from it looks good (tested with oscilloscope).

Everything on the ignition system has been replaced now (plugs, cap, rotor, coil, wires, and the ECU), and checked with the timing light (extensively). This doesn't feel like an ignition issue. The distributor could be a problem I suppose, and I haven't checked #6 since I identified it as a problem. I will check it with the timing lamp tomorrow.

"Sprayed diluted saltwater (helps conductivity) while engine is running to force any ignition voltage loss?" - I'm not familiar with this one, can you elaborate? Perhaps you mean from a spray bottle on the outside of the wires? Again, everything is new, so I'm not sure that would be an issue.

Smoke tested multiple times, hot and cold.

The oil trap system has been removed, but I will recheck everything...

thx,

Wayne

Okay, I didn't know this. So, if 14 and 15 are wired together, then 14/15 --> six wired injectors in parallel --> pin 87 of the DME relay should be .43 ohms.

So, my measured amounts are:

1- 3.1 ohm
2- 3.0 ohm
3- 2.9 ohm
4- 3.3 ohm
5- 3.3 ohm
6- 3.2 ohm

So, these measurements include a portion of the harness that is unique to each cylinder plus a portion of the harness that is shared by the set of three.

Total resistance calculated should be .52 ohms. But if I measure from pins 14 and 15 to pin 87 (with the ECU connected), I get .9 ohms.

If if unplug the ECU (separating the two sides of the circuits), I get 1.5 ohms from pin 15 to pin 87 (through injectors 4-5-6). I also get 1.2 ohms from pin 14 to pin 87 (through injectors 1-2-3).

I guess I'm not really sure what allowable or acceptable resistance is supposed to be through the harness?

-Wayne

From my oscilloscope readings, it would seem like the initial pulse can be sometimes high and sometimes low. The rest of the phase looks okay, although when the motor stumbles, it appears to throw the scope off a bit. I'm not sure if this is the chicken or the egg (causing the stumble, or are we just seeing the results of the stumble).

-Wayne

another question would be ..............is the exhaust system really good for this engine on 914?
When you put on stock muffler it seams the engine runs differently.
Is there another 914 with Carrera engine in the States with the same exhaust system?
I guess you cannot remove it and try different one Pita work,right?

Ivan