loprado

Hi guys, new to the list and after a little help....

I have read some previous posts which seem very similar to my problem.
Which is ('89S4): A very intermittent rough idle (2-300rpm/shaking car). It will never do it as the car is driving, only on idle, usually after warmed up and stopped for a few minutes and then restarted. Within 5-10 seconds the revs will drop and run v. rough. Left for a few minutes I am able to restart with no problems. However this has also happened once on a cold start which confused me! Out of the 4-5 times it has done this in the last 6 months, usally two restarts are needed for it to run fine.
I believe (after reading some posts) that it could be a bad MAF or LH module.
Next time is occurs I want to try to disconnect the MAF and see if it is the problem. Can someone post a pic as to where the MAF is please and what it looks like? Can I disconnect it as the car is rough idling, or do I need to disconnect the battery? If ithe MAF is the problem with the idle even out after it is disconnected?
I also read another post (not sure if it was for a 928) which recommnded cleaning with some sort of injector cleaner/spray.......?
Any help and pics would be appreciated....
Thanks

nicobel

The Mass Air Flowmeter(MAF) is located under the air filter.
You need to remove the air filter, and then the plastic piece that holds the filter. It has two bolts, and it's very easy to remove.
Once you remove the piece, you will find your MAF at the center. Then you can remove your MAF.
BEFORE DOING ANYTHING ELSE: check that the MAF is properly seated and connected, if it doesn't have a good seal, it will make your car rough. DO NOT put any injector/carb cleaner on it, you'll damage it; instead go to your local electronics store and get a can of contact cleaner (non-static, non-residues) and spray a little into it (only when it's cold) ,this will safely remove any residues (if there are) thay may have been a way into it.
I would disconnect the battery before doing this, so the ECU resets itself next time you start the car.


On the other hand, you might have one or thwo vacuum leaks ( ) which are kinda PITA to find and fix.

Gretch

I would look into the idle stabilizer douching first......I use a graphite based solvent, but I have read here that WD40 works just as well. Research it here, the procedure is simple.

Bill Ball

I don't think this is it, but who knows with these cars? Pull the front passenger side carpets and expose the central electric panel. Next to the panel on the outer side beside the EZK brain is the ignition monitoring system relay module. It is a clear plastic box that has two LEDs. They should not be lit at any time. Observe them next time the problem occurs. The behavior you descibe is not what is seen when this trips, but I'd include observing it anyway.

ErnestSw

Generally speaking a bad MAF will not show up just at idle. I agree with Gretch that you should try the WD40 idle stabilizer fix first.

John Speake

Does the idle speed hunt up and down on a 2-3 second cycle ? If not, the Idle valve may be jammed ion one postiton, or the signal from the LH is not present.

Other than idle, how does the car run ? Any black smoke ? Does it pull OK at small throttle openings ?

loprado

Thanks everyone!
I will do a search on the idle stabilizer fix first.
Can I do this when the sympton returns? Or is it more of a 'do it and wait to see if it happens again' kinda thing?
John, Idle speed is steady when this occurs. When it happens the car has almost no acceleration at all, almost like it's running on 4 cylinders, and vey rough. I haven't observed an black smoke but then again its something I haven't looked for when this has happened. I switch the car off straight away and then fire it up again after a few minutes which seems to fix the issue.
Sort of annoying when its just trying something and waiting to see if the problem is fixed!!!
Thanks all for you help......

loprado

Had a read on all I could find about the idle stabilizer. I will still do it but I don't think it is the problem.
My issue only occurs on startup..within 5-10 seconds. It will sit on idle properly and purr smootly, and then just frop to 200-300 rpm as it someone has pulled out half the leads! It has never done it after take off (stopped at lights, etc), or whilst travelling, only immediately after start-up. I left it on for a maybe half a minute to see if it would correct itself, but no luck. It didn't appear as if it was going to stall either, just sit idling roughly. (vaccuum perhaps?)
Over the next few days I will do the idle stabilzer, check all relays for corrosion, etc, check the MAF (maybe not sealed as Nicobel suggests)
If I disconnect the MAF as it's running in this rough state, some other posts suggest that the idle will smooth out if this is the problem.....is this true??...and is it OK to disconnect it as its running??

Thanks~

John Speake

When it starts running rough, check the "ignitiion protection relay" which is mounted on the same bracket as the LH and EZK ECUs (at the side of the passnger footwell)

The relay has a clear case, and if it has triggered then you will see a red or green LED lit.

Bill Ball

That's why I mentioned the ignition monitoring relay. Your symptoms aren't the usual way it presents, but I thought I should mention it as it does kill the fuel to 1/2 the cylinders, and there was one previous report I recall of it tripping on idle. As I said, it's easy to check by removing the passenger side front carpets.

loprado

Thanks Bill,
Well it happened again just now! Cold start, was idling nice for about 5 seconds, then dropped to about 200rpms...I quickly pulled off the front carpets wanted to check the ignition relay, but either it aint there or I'm not looking in the right spot! aargh..No clear case relays with LED that I can see....anyone have a pic?
Anwyay stopped the car, started again after about 10 secs...no problems.
Poured in a fuel injection additive about 5mins ago (after this happened). I've never seen or had an additive that I've noted a difference with but who knows.....
Anyway a pic of the relay would be great...
Fues paneling all looks good, no evidence of water or foreign objects..

John Speake

If you read my post, it tells you to look at the side of the passenger footwell.....

MO Shark

I just purchased an '87 S4 from my boss's grandfather (original owner) with 87k miles and after driving it for the first time I experienced the exact same conditions except mine would stall some of the time.

I joined Rennlist (incredible source of info!) at my mechanic's suggestion and read as much as I could. I did the WD-40 treatment (twice) with no success and was about to do the ICV operation when my mechanic (Imagine Auto in Kansas City) unplugged the O2 sensor and it runs perfect!

May want to look there as well and hope it helps!

Has anyone else had this experience?

loprado

Thanks, will add it to the list of things to check.

Is there a way of testing for a faulty 02 sensor?
Is this located in the fuse panel?

Mrmerlin

O2 sensor is fed into the bottom of the fuse panel at the bottom left you will see a thick wire coming thru the floor find this and try unplugging it it has a barrel connector, Stan