'86 951. The car is missing a little when idling and stumbling on acceleration lacking power. Sometimes it comes around and seems OK for a short period of time(not even a minute), and then it starts stumbling again. Sometimes when you accelerate and let off the gas it will pop like a backfireing sound. I have come up woth the idea that it might me fuel related(like a bad filter?) or maybe vaccuum hose related? Could it be? Also, where is the fuel filter located, cause I have an extra brand new one and I should probably try that first cause maybe its clogged.

Thanks
Mike

 

Also, my extra fuel filter was ordered for an '84 944. Is it the same for an '86 951?

 

I have the same problem when you solve it can you help me out
Whenever I give gas on my '89, it thumps a couple times and lacks the power that it had 2 weeks ago. What's up with that?
-Cyrus

 

I am changing my fuel filter tonite as long as I can confirm that they are the same filter for n/a and turbo, I will re post with the results

 

I had a similar problem, till I tightened my #3 spark plug! Worth a shot to check to make sure the plugs are tight.

 

I am having much the same problem with my 1986 951. Still have not solved it. I think I may have problems in the DME and/or KLR. You can start with a few simple things.

If you think it is fuel related, you can test the fuel pressure and delivery rate.

You can also wiggle some of the electrical connectors, at the TPS, air flow meter, the injectors and the flywheel sensors. With some luck it might be free!

 

Come to think of it, it started stumbling after I pulled out both my DME and KLR. Any ideas?

 

bump

 

My thinking is that after a while (15 years!), vibration and temperature changes take a toll on the electronics. You can have a minute crack in a solder joint and it plays havoc with the way the car runs. Or a degraded contact in a connector which increases resistance. Not a failure that stops the show, just a minor thing. It comes and goes and defies troubleshooting. I have been reading a lot of posts from people who seem to have these types of problems. The turbo's are worse because the have 2 computers, one for boost control.

When I find a solution for my car, I will post it.

 

From what I have heard on the subject, it seems to be the AFM. This is an easy swap, and I may get one soon and let you know if it works, but I dont know yet. I posted this a while ago- search for hesitation problem. This is the link I was sent

http://frwilk.com/944dme/afm.htm

 

I tried that. I pried the little black plastic cover off and cleaned the track the arm rides on with contact cleaner (Radio Shack). I even tried to retrack the arm to a "new" track. It made no change. It still may be the problem, but I am looking elsewhere.

 

2 things to check.

1. Disconnect the battery, then check the connections on your coil. I had a bad (failing) coil, and replaced it with one that had a bad (or I striped it) negative terminal, this caused a slight hiccup as the coil lost and found connection.

2. Replace the "Fuel injection water temperature sender" $39. it is the one below the intake boot, it will have a blue connector (or green if its corroded). This little gem send the water temp reading to the DME to control fuel mixture, cold=full lean to warm it up and melt your catalyst, warm= rich to allow the engine to run cooler.

I found this out AFTER 3 tows, and more $$$ than I care to admit to "throwing" at the problem. HTH

 

I am surprised that noone has mentioned the TPS as a possible source of fault. A failing or faulty TPS can also cause stumbling and loss of power. I have had this problem before and the initial indicators were similar to your description. You might also, while you are checking the spark plugs, closely examine your injector boots. I had a problem once where I started with a stumble, progressed to a no-start, when the insulation on my poor overheated injector boots frayed and allowed the wires to short the injector.

You can also isolate the TPS by simply unplugging it from the throttle body. The car will still run but will cause the DME/KLR to revert to a default setting. You will get a max of 1.2BAR boost, but it will let you check the TPS, since the infamous 'click' test is not always accurate.