02 sensor possible contamination
 

Yesterday in anticipation of replacing my O2 sensor in the next couple of weeks I sprayed a liberal amount of liquid wrench at the base of the O2 sensor were it is screwed into the catalytic converter. I did this a couple of times thinking it would help the removal process. Today the car was difficult to start and when started the engine would barely run. I felt like it was running on three or four cylinders. The engine would stall when I quickly reduce throttle. Is it possible the liquid wrench product contaminated the O2 sensor creating this problem??

Also, assuming this is a contamination issue what is the proper way to clean the sensor??

Thank you for your help, John

Look elsewhere. O2 sensor has no effect on initial cold startup.

Ditto what he said. When the engine is cold, it runs off an open loop map, so the sensor has nothing to do with it. Likewise at full throttle it is running open loop.

I think it's more likely that you knocked something else loose while you were working on the engine.

I agree with the above that the O2 should not cause the current starting/running issues, but if you are inclined to you could always unplug it an force the system into open loop.

If you were in the engine bay working on the O2 connector and not just under the car trying to loosen the O2 sensor itself, the first place I would look would be at the connector for the CHT sensor on the bracket on the left intake plenum. those connectors get super brittle with age and messing around in that area can easily know that connector loose if the plastic has started to fail. try reseating the CHT sensor connector and see if that effects the starting/running. if so replace the connector/sensor as necessary.

Thank you for the replies and recommendations. I will start looking for other possibilities for my problem.
Other recommendations are welcomed.

Regards, John

I did a check of my engine compartment and didn’t find any loose or disconnected vacuum lines. I did find a couple of loose wires connected to a loom that goes to the back of the engine compartment. Looks like these loose wire have been disconnected for years. You’ll also see my broken oxygen sensor connector. I have this part on order from Kroon.
Also, not sure this car has a CHT sensor. I can find this part on pelican for an 84 but not an 83 engine. If I’m wrong about this or you see it in the picture please let me know..
Thanks, John


http://forums.pelicanparts.com/uploa...1679775600.jpg
http://forums.pelicanparts.com/uploa...1679775640.jpg

SCs do not have CHT Sensors. They still use the thermo-time switch for cold starts. It’s on the chain cover just to the left of the dizzy.

Assuming this is a lambda CIS transplant, the "loom" should eventually lead to a control unit under the passenger seat.

How long has the car been running with the 3.0 ?

Hello pmax,

No information as to how long ago the engine was replaced. What was told me the original engine was replaced at about 40,000 miles with a 1983 3.0 L engine with similar miles. The car just turned 80,000 miles.

Do me a favor. Look under your passenger seat and post a pic.

What is this part circled in red ?

http://forums.pelicanparts.com/uploa...1679789363.jpg
That infamous O2 connector is also in the "wrong" place but understandably so, still very intriguing how this was done.

I have no idea about the item circled in red.
I’ll post some pictures I have on file as to what’s under the passenger front seat.

http://forums.pelicanparts.com/uploa...1679791248.jpg
http://forums.pelicanparts.com/uploa...1679791389.jpghttp://forums.pelicanparts.com/uploa...1679791483.jpg

Alright, it does have the right CIS lamba electronics. That thick black wiring goes to the engine loom.

The silver box is the frequency valve/O2 relay, it's a known failure point. Carrying a spare relay is a good idea. A quick test is removing the relay and checking if the poor running symptoms remain the same.

PMax, thank you.
I’ll remove the relay tomorrow and check the running condition.
The engine will still start and run with the relay removed??
I’ll also place an order for a spare.

Start the engine first then unplug the relay for a short while.

Here's a helpful video one of PP's long time denizen made
https://forums.pelicanparts.com/porsche-911-technical-forum/996286-cant-measure-due-cycle-dwell-help.html#post10034405

Alternatively, and arguably a better option given it can't possibly make the engine run worse, replace the relay with the new one first and see if it makes a difference. If not, you still end up with a good relay as a spare.

Hope this helps.

Couple years ago I received a box of various bulbs, switches, and relays. As luck would have it the relay Pmax recommended I change was in that group. Unfortunately no change in the running conditions. I hope to have a friend coming over in a few days with some gauges to test the pressure in the system. I’ll keep everyone posted as to the outcome.

I added a 3.0 lambda engine to my 2.7. The 2.7 has no provision for the O2 connector, so you have to fabricate something or otherwise hold the plugs so they don't flop around.

The red circled black thing is a 12 pin connector (similar to the big 14 pin one at the left rear) for various CIS wires. The black cylindrical thing with a cap is the test port for checking the pulse width modulation sent to the frequency valve. It isn't connected, but with a wiring diagram you should be able to connect it - in stock configuration it has a red wire connected to one of the fuses on the rear panel, a brown wire to ground, and the 3d wire (normally green) to one of the FV control wires. It doesn't affect the operation of the CIS.

The silver cube relay is just a power relay - when on it provides 12V to various CIS Lambda components. The frequency valve is actually controlled by the main "computer" big box, which grounds the frequency valve circuit to create the pulse width modulation. So the relay points close when you start the car, and opens when you shut the engine off. Easy to test the relay - put your fingers on it and start the engine. You should feel it click.

Walt,

I want to thank you very much for the Detailed information. It is very helpful. I did check the relays with a 9 V battery and a multimeter and they both tested OK. Next time I’ll just put my hand on the relay and feel for the click.

I want to restate my problem. This car feels like it’s running on four cylinders. I thought possibly by spraying some liquid wrench on the base of the oxygen sensor I Might’ve created a problem.

Some recent history.
Two weeks ago the car started to develop a cold start issue. Instead of starting instantly it would take two tries before the engine would start without applying gas.
Last week I went on 140 mile drive on some of the back roads in Southern California. There were about 6 to 7 areas where water was crossing over the road due to the recent rains. Water depth ranged from 1 inch to 6 inches. Proceeded through these areas with no apparent problem. On the way home there was a road closure and there was a 30 minute detour of stop and go traffic around the closure causing my old temperatures to elevate up to about 250°. Once through this closure, I pulled over and let the car cool down to about 210 and proceeded to drive 20 miles home. No apparent issues.
A couple days later I was about to go on a drive when I notice my current problem. The cold start issue was not new and was planning to deal with that after a trip I had planned for this weekend.
The fact that the car now only seems to run on four cylinders is my biggest concern. The only changes made to the car between running great and its current condition was the preparation for my 400 mile trip this coming weekend. Checking air in tires and spare, re-torquing in the wheels, just normal things.
The other change as stated above was to apply liquid wrench to the base of my oxygen sensor thinking that would help the removal process when the replacement part was received.

So it sounds like a cold-start issue now. When you havr a cold start problem, you want to check the cold start valve operation. Check that the thermo time switch receives voltage from the CSV, and then shuts off after a few seconds. Test at the connector to the CSV. It's hard to get to because it's in the "triangle of death." Check that the ground to the CSV connector has continuity. If you can pull out the CSV and test it with fuel pump running to see if it squirts, so much the better. Then check the WUR per instructions Tony (boyt911sc) has posted on other threads, or use the Bosch Fuel Injection book. Do you have a CIS pressure gauge setup? You should check the cold and warm control pressures too.

PeteKz,
Thank you for your reply and the areas of possible problems.
I felt the developing cold start issues was probably a different issue versus the car running extremely rough but maybe not.
I hope to be checking CIS pressures in the next few days.
John

John
I can't readily think of a common cause for a cold start issue and a rough, feels like running on only four cylinders, issue.

But for sure spraying penetrating oil on the O2 sensor where it screws in isn't part of either issue. The sensor plays no part in starting the car, and it is hard to imagine how its failure (which likely results in a 0 voltage signal no matter what the AFR is) would cause either of your problems. These cars run fine without the sensor - they just don't get the fuel mileage they otherwise would, and may not meet emissions standards. At idle, and at near full throttle, the CIS's frequency valve is controlled by a throttle switch.

A CIS pressure testing tool isn't expensive, or at least doesn't have to be. It consists of a pressure gauge (inexpensive part), some hoses, an open/closed valve, and a bunch of threaded adapters so it can be used on a variety of cars and injection systems. You can spend a lot on one if you want, but the less expensive ones work just as well. Shop around. It is really the basis of troubleshooting cold start issues (at least once you have confirmed that the cold start system is working, which doesn't require a specialized tester). But testing the CIS is how a mechanic starts figuring out cold start issues once the the functioning of the cold start valve system is shown to be fine.

Rough running could have lots of causes. A vacuum hose dislodged from the distributor? If you had spark plug wires off the plugs or off the distributor and plugged two into the wrong places, that would do it, but you'd not likely have fiddled with any of that just driving round. Check the spark timing (calls for a timing light). Did the distributor come loose? Is the distributor cap OK? Is its center electrode OK? Rotor OK Cap on tight? A little bit of apparent wear on this stuff is normal and not a problem, but something broken is.

One approach is to pull and inspect all the plugs - any too rich or too lean? Are all the gaps reasonable?

Another tool a mechanic would use is a leak down tester. That will tell you if you have significant compression leaks around rings or valves. If a valve adjustment has gone way wrong, so a valve doesn't close, this would catch that (typically failure here results in too lose a rocker adjustment, with attendant excessive clicking noise).

Plus, with the valve covers off, you can fairly easily check for broken valve springs. I'd put that well down on the list, as the engine runs well with one of the two springs on any valve broken until you get up to 5 or 6K RPM.

In the old days of carburetors, the mantra for bad running was check the ignition first, then move on to the fuel and other systems.

Having basic things out of whack would certainly not help starting the car, especially when cold, so there could be some connection.

Or is there a shop near by which has experience with air cooled 911s? Differential diagnosis is a great intellectual challenge, but isn't always easy.

Walt,
Thank you for your message. I’ve been looking at CIS testing pressure tools but this issue developed before I made a purchase. As recommended I’m gonna start at the beginning and test pressure. I have a friend coming over in the next couple of days with a set of testing gauges.
Interesting from just a few days ago I could get the car started and apply throttle to get the RPMs up but felt like it was only running on three or four cylinders. Today, wanting to back the car out of the garage onto my scissors lift I had to restart the car 20 times to develop enough pressure beyond a weak idle to move the car. The throttle was not working at all. So it’ll be interesting to determine the final fix and I will certainly share with everyone. I appreciate your participation.

Thanks again Walt I appreciate your comments.
John

A little more history I just thought about. Probably 400 miles back I had to replace my fuel pump. I also replaced my fuel filter as preventive maintenance. I would not think any of these changes has anything to do with my current issues but ………

Want to close out the thread and thank those who offered suggestions and help. I had a friend come over and put a set of pressure gauges on my car. He felt the warm up regulator was defective. I went with his decision and removed the warm-up regulator and sent it out to be rebuilt. The rebuilt unit arrived this afternoon. I installed it on the car and everything is back to normal. The only glitch was I decided to replace the fuel line between the warm-up regulator and the fuel distributor. My replacement line leaked. I had to reinstall the old fuel line. Went for a quick drive around the block and will give it a longer test drive tomorrow. Thanks again for those who offered suggestions.
Regards, John.

Well, that's all to the good.

You had a cold start issue and a "feels like it is running on only four cylinders problem.

Cold starts problems can be due to the cold start feature of the WUR not working correctly, or the cold start valve not working, or the ECU not getting power. From the resolution here, it looks like it was the WUR.

The WUR is designed to provide a rich fuel mixture when the WUR (and the engine) is cold. As things warm up (the WUR has a heat coil inside - that's what the wires to it are for - and eventually engine heat warms it) the fuel mixture gets leaner. That's why the specs call for a cold control pressure, and a higher warm control pressure. If this system fails, cold starts are a problem, but not warm running.

Another thing which can cause WUR troubles is a clogged filter inside the WUR. This makes both cold and warm pressures leaner, which affects starting, and also running. I'm not sure that it would be so lean that it felt like running on four cylinders, though.

To close the loop for those who have tried to diagnose things remotely, could you be specific as to the results of the tests your friend did? What cold and warm control pressures did he find? What was the system pressure?

Walt,

He only did cold pressure test. What made him believe the WUR was defective was the cold control pressure was over 5 bar. I will have to ask him about the system pressure number.
The company who did the rebuild confirmed the unit was “no good” before the rebuild. Unfortunately they didn’t give any details.

Thanks.
5 bar is about system pressure, which is what you get with a clogged WUR filter. CPs range from about half a bar to 2.5 bar depending on temperature. No wonder things weren't working right. This filter can be cleaned in at least some cases by taking the WUR apart to flush the filter. I did that on mine. But purchasing a known good replacement is easier for most.

How the filter gets clogged is an interesting question, since there is a pretty efficient external fuel filter in the system. But it happens. I wouldn't expect changing to a new filter would send a flood of crud into the fuel distributor to end up in the WUR. So the how seems an unknown.

Also, you can see why guys like Tony start out by asking that the person with a problem do the CIS pressure tests. Pointed to the problem right away.

Interesting the engine still started and ran with the CCP so high due to the clogged WUR.

Pmax,
In the end it would barely start and idle. Had to restart it 20 times or so to move it from one side of the garage to the other. There was no throttle response at all.

Pmax
I think the CIS is surprisingly fault tolerant, at least when it comes to being able to start (eventually) and run (however well or poorly). When I converted to a Lambda 3.0 I left off the Lambda part. Why would I need that stuff, run that wiring, etc. It was hard to start, at least when cold, but started. Seemed to run OK just driving around. Then I wised up.

With the Lambda the FV runs PWM 50% duty cycle for starting. That 50% affects the FD differential pressure so it is lower, doesn't it? So more fuel flows to the injectors. Without the effect of the FV (I assume it is closed if unpowered, so has no effect of the lower chamber), what is the lower chamber pressure? System?. But isn't the Lambda FD set up to run a lower chamber pressure which is always reduced some by the FV? Or the upper chamber system is set to work a bit differently to compensate for a different base lower pressure? Just curious.

But it ran without noticeable problems (who would notice some HP loss driving around town?).

I don't recall why I ran the pressure tests which caught my clogged WUR filter. I'm sure the car ran. I was mostly fiddling with CPs (I'd made my WUR adjustable for CCP but also WCP as it seemed to have too lean AFRs racing, which I tried to fix - everyone said it was because I had the wrong WUR, but I have the same issue with the "right" one). When I saw system pressure when reading CP I took the WUR apart and fixed that problem.

Sounds like John's blockage was worse than mine somehow.

So yes, it is interesting.

As far as I understand, a closed FV, equivalent to 0% duty cycle, the end result is less fuel to the injector. So if the system is designed to run at 50% nominal duty cycle, I agree that means without the FV working, it will run lean. With the O2 sensor disconnected but lambda CU still driving the FV, the system runs at 50% duty cycle but in your "lambda delete", I assume the FV was always closed so that means the car runs lean unless the WUR has been adjusted. I recall reading that thread of yours where you adjusted the WUR which is what I did to my WUR as well but in my case CCP was low so I had to lean it out.

I'm speculating the CSV was injecting enough fuel each time to eventually "run" the engine, sputtering, even with the CCP that high. The 20 start attempts to get across the garage makes sense to me.