Rick's Shark

I am a new Rennlist member and the new owner of a 1987 928 S4. Yesterday the car started to run badly, loss of acceleration, mis-fire, and not idling. The car stalled on the highway and I was able to restart it and by keeping the throttle in one constant position limp home. I thought maybe a injector but a friend said the MAF. I remove the MAF this afternoon and the hot wire is in place and not broken. I would appreciate any input.

Thanks -

Stromius

Contact Injection Labs (Kevin). They will test your MAF and rebuild if needed for $175 with 2 day turn around. www.injectionlabs.com Located in Boulder, CO.

Rick's Shark

Thank you - do the symptoms sound like the MAF sensor to you?

Stromius

Contrats by the way too on your S4!

Stromius

Yes it does sound very similar. Rough starting and running and loss of accelertion etc. My hot wire looked fine too but even using MAF cleaner didn't give lasting results.

PCARUSA

Yes - It does sound like the MAF. I had the same symptoms about a year ago. I also had black
smoke at idle. There is no warning per se when the MAF goes bad. The new one fixed it.

Rick's Shark

Robert - was the hot wire broken on yours?

linderpat

Before I start tearing off the intake and ripping out the MAF to send for a fix, I certainly would first look for a disconnected vacume line or a bad relay for the brain or fuel pump.
There could be many less onerous things than the MAF at issue here. Always eliminate those first. Do a full search of the sypmtoms here, and see what you find.
If on the other hand you have someone close by who will swap out a known good MAF for a short test with your engine, do that too. In fact, Roger at 928rus will sometimes send one for just such a test. Good luck and keep us posted

EDIT - I see you already have the MAF off. Look for the easy stuff still, tho.

Mrmerlin

I would do more checking just swapping out parts isnt the way to fix your car.
Do you know when the brain was rebuilt?
Usually a MAF will slowly degrade a brain will fail sometimes suddenly.
Is the tach moving when you crank it over? do the injectors click with the key turned on to the run position?
Have you checked the coil wires for shorts, I would remove both coil wires from the coils and distributor caps and look at the ends and inspect the spark plug wires for cuts or shorts an easy way is to open the hood and start the car at night,look for the fireflies if you see any then i would recommend that you buy a new set of ignition wires, The best i think are the factory Beru about 395.00 from Roger, they are already laid out and numbered they come with the wire protectors and they should last another 20 years

Rick's Shark

Thanks Ed - I appreciate it !!

PCARUSA

No. My wire looked fine. Actually I didn't think it was the MAF but it was the problem. The best
way is to find someone who has car like yours and ask to 'borrow' his MAF and see if that is it.
Maybe there is a Rennlister near you. I live near Los Angeles. If you live close you can borrow mine.

Villen

I have my MAF on my table. Tested it like JDS recommend. Pulled it out and sure enough ran OK on the Limp Home. Following Stefans advice and sending it off. The part I get back will be superior. Already replaced O2 sensor & plugs so what is another $175 for something that appears dead. Not the ideal diagnostics but works for me.

outbackgeorgia

When my MAF failed it would not start until the MAF was unplugged. It ran, barely, better at about 2500 rpm without the MAF plugged in.
I have driven mine with both failures and they are different. Also the LH was intermittent, would run fine, then not run well at all. When the MAF failed, it simply would not start.
Not sure which you have, but you will have both eventually.
Where are you located? Much easier for someone to loan you a part if we know your location.
It could also be the LH computer, similar but not same symptoms. I have experienced most of the failures. MAF, CPS, Hall sensor, LH computer failure, oil galley plugs loose, etc.
Dave

Villen

I am a little tardy on reporting the results of the advice given/taken. On my personal experience with the car I felt that Stefan (Stromius) said little but was on point. This was not a reply to my question, but it applied to my problem. I called Injection Labs and shipped my MAF on Saturday, they got it Monday, shipped it back Tuesday, I had it Wednesday and the car was on the road on Thursday. Now that was a satisfying moment. This is a wonderful resource. Thanks guys.

Boaf 32

Dave, All.

Good thread. I've had my 1986.5 928S for 12 years and kept up on belts and other demons. I believe I too am starting to experience the MAF symptoms described. However, after my car is warmed up, it goes away.

• Car starts fine
• Had the "mouse nest" collection of grass over the intake and cleared that out
• New plugs less than 2000 miles ago.
• Yet to put a new fuel filter in (on the spring list).

So my question: Is there some type of test for MAF and TPS? I can check the connections as well.

Thanks,

Boaf