My car is a '99 C4 with a reman engine...53k miles on the car with 10k miles on the new (to me) engine. For months now it's been stuttering when I hit the gas after a cold start. It seems to idle just fine, but as soon as I get it out on the street it stutters and bogs down when I hit the gas pedal very hard at all. It usually does this for a minute or two and then operates perfectly normal.

Any ideas? TIA!

 

Hey Jake, you aren't stomping the throttle when it's cold, are you?

Check around the throttle body and intake runners for any lines that may have cracked.

Sounds like you are facing a small vacuum leak that is null once the engine is a little warmer.

 

Try running a bottle of Techron through it. I've had pretty good luck with the product both in my 997 and my 996. I was very skeptical, but it seems to me that it helps quite a bit. Of course it could be something else entirely with your car, but Techron is a cheap fix if it works.

 

Check the AOS

 

Nah, I'm not stomping on it...barely breathing on the pedal makes it stumble, then it catches and goes just fine. It might do this four or five times, then it's like the problem works itself out and it's just fine till the next time I do a cold start again.

Can't hurt...I'll give it a try. Thanks!

I guess I assumed that it couldn't be that because it works itself out so easily and I've never seen any kind of smoke from the rear...do you think it's still a possibility?

 

I have this same exact problem. What works for me is "priming" the fuel pump, turning the key to "on" but not "start" and letting it sit while I buckle in and whatnot. Then when I start the car the stuttering issue is mostly gone.

I figure I'm losing fuel pressure while cold, not really an issue and I basically forgot about it since it just became habit to do the key trick so I forgot about it. Really should check into it though.

 

Hmm...I already do this, but maybe I'm not waiting long enough. I'll let it sit with the key on for 20-30 seconds before I crank it next time in an effort to narrow it down. Thanks, Dave!

 

I had no smoke except a puff on startup. On cold starts (the colder the day the worse it was) the engine would stutter and sometimes stall. Frequently the engined revved high on start and then ran rough until it warmed up. After a new AOS all was well. It can be easily checked by someone with the right tool.

 

Old post, but did enyone find a solution for this?
My car seems to have same symptoms, starts fine and idles well. Drives good if you don't push too much gas. Symptoms go away when the temp reading are roughly 50deg Celsius.

It souds like it's running lean, so I think it's the temp sensor or maf.
My temp meter works, but is there different sensor for ecu?
Allso, whats the sensor in intakemanifold?

 

Are you talking about the MAF(mass air flow) that is in the platic air box to the throttle body? A picture would help.

I always let mine run for two minutes till the idle drops then I go seems to prevent this hesitation people talked about.

 

No, not the maf.
It's in the right intakemanifold, between intakerunners. Top of the plastic intakemanifold, right about where the ac-pump ends.
Just ordered the Durametric so I can check all the sensors.
If all the sensors are ok, I think that the intake leak is the problem.

 

Ice in the carbs

How often is it driven. Maybe even some moisture in the fuel. I jnow I don't like alcohol in fuel. Darn stuff lets the water suspend in the gas.

 

while running, open up the oil cap.... see if it still stumble, if not check the seal "O" ring of the cap.... it might be cracked and will loose vacuum.

 

I drive it daily. Heh, and no carburators. Fuel is 98oct(RON) and contains max 5%ethanol
I have a fresh tank of fuel.

 

Tryed the oil cap, idle stumbles when it's removed. So no leak there.
I think it's temp sensor fault.
Like I mentioned before, engine sounds like it's running lean.