944 S2 warm idle problems

aaron · 04-05-2002, 02:09 PM

When I start my car when it is warm and has been driven, it occasonally starts idling up and down and the check engine light stays on until it stops doing this. About 15-20 seconds. It then idles pretty well. It is like it is going to stall. It idles form about 900 to about 500 or less I would guess. Any ideas? I have not changed the O2 sensor. And have no receipt from the PO about this being done.

JGriff · JGriff's Garage

Quote:

Originally posted by aaron
When I start my car when it is warm and has been driven, it occasonally starts idling up and down and the check engine light stays on until it stops doing this. About 15-20 seconds. It then idles pretty well. It is like it is going to stall. It idles form about 900 to about 500 or less I would guess. Any ideas? I have not changed the O2 sensor. And have no receipt from the PO about this being done.

I’ve been experiencing the same since I bought the car, but my check engine light does not come on.

I recently changed the O2 sensor, and it has seemed to help a bit, but the car still does it every now and then. There isn’t a pattern to it, which makes it very difficult to diagnose.

I’ve heard of other owners experiencing it, and I haven’t heard of a definite solution.

Jim

Makis · 04-05-2002, 03:05 PM

I would check if you have any vacuum leaks first. Then I would check if all the sensors are connected properly and all connectors are clean. Particular attention to the air flow meter and throttle switch. Then I would inspect the spark plugs color. If anything is not right with the spark plugs I would do a compression test to make sure the idle problem is not related to a mechanical failure. Best of luck.

riff · riff's Garage

My S2 suffers this same problem....I've done a couple things to try to fix:
1. New fuel pump check valve
2. New O2 sensor
None of these has worked. I think the next thing I am gonna try is to change out the Idle Stabilizer Valve. I haven't given it a real close look, but the trouble is looks like you'll have to pull the entire intake off to get at it. The fluxing idle hasn't bugged me enough to make it a priority. Oh well, everyone needs weekend projects.

Cheers,

marko · 04-06-2002, 08:59 PM

My S2 cab also has a rough idle. It is very intermitant. It happens about once or twice a month. The idle will all of a sudden
drop to about 600 rpm and idle very rough. If I step on the gas just a tad, it will almost die. If I step on the gas hard it does rev up. After a little while (10 minutes on average), everything goes back to normal and it runs fine. hmmmm

Makis · 04-06-2002, 11:55 PM

Intermittent symptoms like this is certainly related to sensor connection problems. Try cleaning the air flow meter, the throttle switch and the water temperature sensor connectors first. Also as someone else said here you may have a sticking idle stabilizer but access to it will be difficult. So if you lucky the clean may just do the trick.

JGriff · JGriff's Garage

Quote:

Originally posted by Makis
Intermittent symptoms like this is certainly related to sensor connection problems. Try cleaning the air flow meter, the throttle switch and the water temperature sensor connectors first. Also as someone else said here you may have a sticking idle stabilizer but access to it will be difficult. So if you lucky the clean may just do the trick.

Where are all of these located? I do not have a repair manual, nor a CD that shows the location.

Or is there a website with pics?

Thanks for your feedback. When I get a chance, I'll look into cleaning them all (after I find out where they are all located, that is...).

Jim

Makis · 04-08-2002, 05:50 AM

If you are not confortable with opening connectors and cleaning them then don't attempt to do it yourself.

However the the air flow meter is located in front top right of the engine and is connected to the inlet manifold via a large rubber pipe. There is a wire connector to the left of the meter. This is the connector you can open up and clean and put it back.
The thottle switch is locate further up on the throttle body which in temp is bolted to the inlet manifold. Here again there is a connector that you may remove clean and put back.

The water temperature sensor is bolted on the engine block and is located at the top front of the engine on the same side of the air flow meter and just underneath the edge of the inlet manifold.

And finally the idle solenoid is underneath the inlet manifold still towards the front of the engine. You can only access it if you remove the inlet manifold. You may be able to spot it if you look under the inlet manifold.

Best of luck.

And yes, a final tip make sure you have a telescopic magnet stick in case you drop the connector clips in the engine bay. They are difficult to extract without it.

JGriff · JGriff's Garage

Quote:

Originally posted by Makis
If you are not confortable with opening connectors and cleaning them then don't attempt to do it yourself.
...SNIP...
And yes, a final tip make sure you have a telescopic magnet stick in case you drop the connector clips in the engine bay. They are difficult to extract without it.

Thanks for the info. I did some cleaning of the connectors, as well as the DME relay (whose electrical tabs looked a bit tarnished... so I sandpapered them clean), and the problem has been fixed!! (Well, so far it hasn't happened again... my fingers are still crossed!!)

I also found that the throttle cable had some slack in it, so I adjusted that so that it was snug. What a difference that made!!

I don't know what really fixed the problem (although if I had to take a guess, it would be the DME relay... it looked the worst as far as it making a good electrical connection), but I'm sure glad that the problem is gone!!

Oh, and your suggestion about the magnetic pickup was a good idea. I needed it once. Those clips sure are small and springy!!

Thanks again.

Jim

JGriff · JGriff's Garage

My problem has been cured!! Yeehaw!!

I brought it in to have it checked out (by Bill Pfister at Eurotech in Framingham MA... great guy/place BTW), and I ended up replacing both the Throttle Position Sensor and the Idle Adjustment Valve.

First, he checked for vacuum leaks. All was fine. He then checked the TPS, and said that it needed to be replaced. After replacing the TPS, he said that the idle still wasn't quite perfect (i.e. still some erratic movement), so he went ahead and replaced the ISV.

I took a look at the old ISV, and it definitely needed replacement... it didn't move freely, and it wasn't opening/closing all the way.

The car now idles perfectly smooth.

Hope that helps.

Jim

Aron313 · 07:39 PM

I have some problems with my 944s2 as well. When the car is cold, the rpm jumps a lot. When the car gets warmed up, it still jumps but not nearly as bad, but the oil pressure fluctuates a lot during this time. The weather has just started to get cold so im not sure if this is a normal occurrence for the change in temperature or if there is a problem. This all occurs when the car is idling.

Also when the car starts after being really cold it has a whine to it. This also just started to occur.

ried · 12-18-2013, 11:51 PM

Aron313, you've just resurrected an 11 year old thread

Please be more descriptive. Does your car have an unstable or erratic idle speed? How drastically do the RPMs fluctuate? What about when you apply the throttle?

What does your oil pressure gauge read when it's fluctuating?

Aron313 · 12-19-2013, 03:56 PM

Well it tends to move up and down within 200 rpms really rapidly and idles at 1000. When any gas is applied it goes back to normal until it starts to idle again. And the oil pressure is fluctuating a lot around 3. But when the car is cold it stays steady at 4

Sorry im new to this and didnt notice the age of the thread.