mytrplseven

After changing the AFM, TPS, DME, fuel injectors, vacuum lines, ignition system, fuel pressure regulator, fuel pump, fuel filter, strainer, air cleaner, oxygen sensor, ref sensor, fuel injector connectors, Oil cap seal, AOS seals and catalytic converter I still have a stumbling acceleration problem during normal acceleration.

On Friday I did another vacuum leak check and really looked deep into the guts of the motor. I noticed bubbles coming out of the hose where it fits onto the AOS. So I pulled the intake manifold to get at it and in the process, found 2 of the 4 intake manifold gaskets weren't in the proper orientation. The little notch in the gasket was not where the injector sprays into the head and so I was convinced that this, plus the AOS leak, was the final solution (poor choice of words, I know).

Today I put everything back together and it still stumbles while accelerating. WOT works fine and it idles just as it should. At this point, I'm simply out of answers.

I don't dare take the car to the dealership where they charge $135 an hour and don't really have a 944 tech in their shop. So now I'm wondering what the next step will be.

MB968

Wish I had more advice, but don't know our systems that well yet. But, if you could capture info from the DME during the stumble, you may get some clues. I'm not aware of what the Durametric will do, but if you have one, I'd see what things you can monitor. I had an aftermarket ECU on my Mazda that I raced. It was easy to look at all the info to help in figuring out issues such as this. Good luck hopefully someone else has a few clues.

odonnell

Is there any way a bad fuel dampener could cause low pressure surges during non-steady state flow? I know it relies on intake vacuum and works with the FPR to maintain the correct pressure in the rail - just a thought I had. May not even be close.

mytrplseven

I wondered about that but it was never addressed in any of the diagnostics write-ups I researched. Since I passed all the fuel system checks per the manual, I didn't expect it would be suspect. What's another $80, right?

odonnell

I have one from an early car in the garage. If you want to try it out, just pay shipping.

jagdhund

lol especially when talking about a german car.

Van

Just out of curiosity, have you done a compression test?

And, is there any chance that it could be drivetrain related? Like a slipping clutch, or a bad CV joint?

Noahs944

Another area to investigate is the DME (inj) coolant temp sensor & wires and throttle adjustment (the 7mm screw-although I assume you've looked into that).

VirginiaF1

1. DME Temp Sensor acting a fool.
2. Your new O2 Sensor giving bad partial throttle data.
Sorry for your issues man..

konakat

You could try running without the O2 sensor. It would eliminate possible wiring issues, and also simplify the DME operation in case there is an issue in there.

mytrplseven

I saw that possibility mentioned on a previous quote and have considered disconnecting it to see if it makes a difference. It's a new sensor, as is the cat. I borrowed a good DME to narrow it down but it didn't change the symptoms.

mytrplseven

The DME temp sensor is new. The engine stumbles in cold and warm engine temps so I've ruled that out.

mytrplseven

Yep, done all that. Thanks

mytrplseven

New Sachs clutch and transaxle serviced. CV's are good and the RPM doesn't waver during the stumbling. Works great at WOT.

944Ross

I don't see any mention of the AFM... bad spots or dirty wipers?