cjoenck

Need help... My 1991 C2 Tiptronic does not want to accelerate when cold. As the engine warms, acceleration becomes normal. Here is what I did so far - some related to other issues:

- Cleaned ISV (the car idles fine)
- New coils
- O2 sensor is about 3 years old
- New DME relay (fuel pump runs fine)
- Distributor caps and rotors are about 3 years old
- Distributor belt is fine
- Spark plugs are 4,000 miles old
- Compression and leak down check out fine on all 6

What am I missing?

Thank you for the help.

jimq

mine started doing the same only it works fine the first start of the day. If it sits for a few hours it acts like you say yours does.If it sits overnight it works normal again. I havent tried to find the problem yet but I have run scantool and get no codes from the DME or the TIP computer.

cjoenck

Lack of acceleration is actually so bad that I can put the pedal 1/2 way down w/o any noticeable immediate acceleration. It is almost like the needs "to think" for a minute before it starts moving faster. I have no codes on the scantool (Durametric).

Rocket Rob

If you put the tranny into neutral, does the engine rev willingly? I'm wondering if you have an engine problem or a tranny problem.

cjoenck

Good point - it is definitely the engine. Same behavior with tranny in neutral. It appears to be engine temperature dependent. Engine cold = equals bad acceleration, engine warm = good acceleration.

Rally Guy

Could be AFM?

Haven't heard of an AFM being so temp sensitive - but it sure sounds like worn substrate on the AFM. Perhaps as the AFM warms - conductivity increases and throttle response returns.

Lots of AFM diagnosis. fixing info in this forum.

RK

964TOK

Have the same issue. Clears itself after about 400 yards.

Flip it accross to manual mode and slowley put the power on.

Would like to know what is causing it though.

cjoenck

Great to hear I am not the only one out there with this issue. So I have tried to think this through - with the incomplete knowledge I have.
Since it does not seem to throw a code, I have to eliminate cylinder head temp sensor or O2 sensor. I replaced my o2 sensor 3 years ago.

Maybe this is connected to another symptom I have noticed for a while - trying to start a warm/hot engine after about 20 - 25 minutes is impossible w/o some throttle. I get an engine warning light for a couple of seconds and then everything is fine. Starting after 5 minutes or 45 minutes is no problem w/o throttle.

Sooo, could this have something to do with the fuel pressure regulator? It is supposed to maintain fuel pressure to the injectors for about 30 minutes to help with warm starts. It is a mechanical valve, sits under/behind the throttle body and has a vacuum controlled diaphragm. Maybe this is just an old fashioned fuel pressure problem?

It's one of those issues that really bug me... Anyway, I would appreciate any obvious (or not so obvious) errors in my logic....

Thank you!

jimq

My problem only happens after the car has sat all day like after driving in the morning to work. When I go to leave at night it has the power loss. If it sits over night it fires right up and runs normal. Its almost like a switch isnt resetting itself as the car cools down until it has fully cooled overnight. Almost like a choke type problem. I have no hot or cold start problems at all. It always fires right up.

964TOK

Agree with Jimq, best way to describe it is like a choke type problem