Paul Bakker

Sorry but did'nt find the time to check the LED presence. As soon as I know I'll let you know. My full attention went to the WD40 action today (and some regular non Porsche work).
I filled the intake hose up with WD40 and I'm curious if this has any effect tomorrow.
Keep you informed.

Paul

James Bailey

Actually in the early stages of thrust bearing failure it DOES stall at idle but will restart nearly NORMAL. Later in the process yes it makes the car crank much slower until it will not crank at all until it cools down. Drive it more and it gets where it will not crank at all.... Several new owners of S-4 cars have also experienced this with the same end result. However the most common cause for an erratic idle searching and stalling is the idle stabilizer valve. If the car is way down on power then it could be running on four cylinders but that means only 1/2 the horsepower which is pretty obvious.

Paul Bakker

No slow crankover noticable. Didn't see any LEDs flashing nearby relay-board. No misfireing, not on 4 cylinders. Engine picks up as should be. When revs > 1000 problems gone. <1000 RPMs and problems arise.


Should the engine stall when this hose is closed by ie a finger ???? If so I can check if a vacuum leak is somewhere. When I put WD40 in couple of days ago and put some low pressure air in it the WD40 came out of the 2 air intake hoses so back through the airfiler. I presume everything is lubricate enough then.

Poured a different chemical (carb cleaner) into the hose. No effect. One can hear it changes the REVs for a short while but I think that I can expect when mixture is upset.

We've been a couple of days further now and I've notices something interesting.
When engine is cold after starting everything is normal (about 750 revs/minute) until engine gets hotter. Around 70 degrees problems suddenly begin to rise.
Sorry I didn't do all the technical stuff you mentioned. I'm no mechanic but I'll try to seek as far as I myself can go. Have learned a lot already and that's also nice.

Thanks,
Paul

Leon Speed

That's a lot of lubrication!! Problem is, most probably didn't reach the ISV. Most got sucked into the intake and burned in the cylinders. The hose leading to the ISV is nr. 11 in this picture. So the best way to get at it, is to remove the MAF and then with a long straw through splitter nr. 8.

Paul Bakker

So through ring 18 furtheron I presume ?
Began a couple of days ago by removing the MAF sensor and putting WD40 directly into the big black pipe below but I now understand that wasn't correct.

Do you mean I put a straw into the side of it to reacht the splitter ?
or
Do you mean I go looking on the outside of the big black hose and disconnect no 18 and pour it with carb cleaner ? It seems the last is very difficult because of the narrow space there.

Did you do this job yourself sometime ?


Thanks.
Paul

Leon Speed

This picture helps more, the picture before doesn't show how the ISV is connected. The red line shows where to spray. Usually WD-40 cans have a straw to put on the nozzle, use that to at least get by the splitter. You have to remove the MAF. Yes I did this once and I remember having to loosen the big black pipe on which the MAF sits in order to get to the splitter. That wasn't easy because of the tight space but it can be done.

Paul Bakker

Thanks for the pic.!
It clarifies a lot. I'll do a last effort to get the carb cleaner/WD40 to the idle sensor by blocking the hole in the large black pipe with my finger and then pouring in the cleaner into the hose. In this case the liquid should find it's way to the idle sensor.

One last question:
I've noticed on a COLD start there's no problem until the engine gets hotter (>+/-50 degrees). So during this warmup period there's NO problem with idle. Is this something one can expect when the idle sensor is "sticky" ????
Is the car during warmup running on some kind of "cold engine, richer fuel" program and is the idle sensor maybe bypassed during this stage ???

Thanks.
Paul

SQLGuy

There is no "idle sensor".

The device you're trying to lubricate is the idle stabilizer or idle air valve or idle air control (ISV, IAC). It is used quite heavily during cold starts and the warmup cycle.

What is bypassed during warmup is closed-loop Lambda. I.e. the oxygen sensor and the LH computer's logic to adjust mixture to obtain a properly lean mixture based on the readings from the exhaust. Normally this doesn't come in until the car is a bit warmed up, and it is disabled above certain thresholds of load, throttle position, and RPM.

Also, immediately after start, there will normally be a few seconds of extra fuel for after start enrichment (ASE), and then a few minutes of warm up enricment (WUE). WUE is normally a pretty gradual taper, lasting until the coolant temp sensor shows the engine to be at "normal operating temperature."

928's warm up pretty quickly, so I'd guess that it's either the end of WUE or the cut-in of closed-loop Lamba that you're hitting when your problems start. Someone with access to 928 diagnostic tools could probably read out sensor data from the system and diagnose this immediately. Otherwise, I'd still be looking at the O2 sensor, the MAF, and the possibility of vacuum leaks.

Knowing what the plugs look like a few minutes after hitting the problems (nearly black = too rich, or bright white = too lean) would be helpful. Did I ask about this earlier in this thread?

Paul

Paul Bakker

------------------
Quote:
Originally Posted by John Speake
Sounds like your ISV is working fine, that's why the RPM cycle up and down.

I assume your car has cats ? Might be a prolem with the O2 loop. Unplug the O2 sensor, do a battery ground disconnect for a couple of secs, reconnect and try the car again.
---------------------


This WAS the solution to my quest!!!!
Did exactly as you said and took the car for a test run. No problems!

Can you tell me WHY a ground and O2 disconnect/reconnect solved this problem ??? Is the O2 sensor always powered by the battery and was it in error (like my former windows XP computers always did ) ?
Please inform because I want to know if this problem can arise again and I'm just very curious!

THANKS A LOT FOR ALL YOU INPUT!!!

SQLGuy

No, the O2 sensor is not always powered. It is turned on when the engine is started, and takes a few minutes to warm up. You probably had a bad connection to it. Depending on why the connection was bad, the problem may come back.

Do you know when the O2 sensor was last replaced?

Paul Bakker

No idea....
If it was a loose connection it should have been in the part where the two cables connect nearby the relay box because this is the only part I touched beside the main ground cable in the hatch.
I did clean the ground connection cable with sandpaper, I saw a tiny little bit of whiteness there.

Thanks.
Paul

John Speake

OK so do you now have the O2 sensor disconnected ?

Paul Bakker

What I did:

Disconnect O2
Clean ground wire
Start engine with O2 disconnected
Waited for the engine to reach 80 degrees -> no problem, normally I had the problem when hitting 50+ degrees.
Stopped the engine
reconnected the O2
Waited several minutes to see if engine idle went up/down -> no problem
Took the car for a drive -> no problem

Thanks again!

John Speake

Well, you need to drive the car for about 10 miles for the LH ECU to fully adapt. Then see if the problem has gone.

Sometimes a battery reset can fix a problem like yours, but it's rare.

Paul Bakker

I did drive it for 10 miles without any problems.
I've been looking for a solution for a week now and every day I had this problem ALWAYS. After the actions I descibed the problem not once came up so I'm pretty confident my problems are over (for now).

We'll see how long it will last and when problems arise my focus will be on the O2 sensor.

Thanks.
Paul