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YOUR RESEARCHEngine stutters when cold
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almost the same
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Reported cause
Then when I start the car the stuttering issue is mostly gone.
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It can be easily checked by someone with the right tool.
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- Take out and cleaned the oilfillertube, seems that it had a small leak in o-ring that is on the block side.
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But all worked out: The replacement MAF started acting up -- I made a better diagnosis this 2nd time -- and on a hunch I dug the old MAF out of my car parts stash and installed the old MAF.
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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.
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.
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.
You can almost eliminate the MAF by disconnecting it at the wiring harness, clearing the DTCs (even if there are none this resets all the learned fueling to the defaults) then driving the car as you did when the symptom/behavior appeared.
If the behavior/symptom gone... MAF is #1 suspect. Since these are so expensive you want to be sure though.
Be sure the oil filler tube cap is not leaking. (The original one on my 02 Boxster was leaking (I couldn't hear it but a co-worker did). My missing this leak caused me to mis-diagnose a MAF as the cause and replace a perfectly good MAF when a $15 cap was the real fix. But all worked out: The replacement MAF started acting up -- I made a better diagnosis this 2nd time -- and on a hunch I dug the old MAF out of my car parts stash and installed the old MAF. Old MAF worked just fine and it is still working just fine.)
Anyhow, get an OBD2 code reader/data viewer and prior to or at cold engine start verify intake air and coolant temperatures are close to ambient and each other. Verify neither jumps up (or down) at engine start or after as the engine's idling/warming up. If you see for instance the coolant sensor reading high the engine controller will be misled into believing the engine is warmer than it is and run a leaner mixture which can account for the behavior you observe.
Sincerely,
Macster.
Check the air filter lately?
Yah sure the electronic adjust for airflow but that doesn't mean it like slower air flow.
-20 ??? You ought to be ashamed of yourself. Maybe try getting the air intake to fed off engine compartment air thats a bit warmer.
Well, on my car this problem is almost the same. It will do it always when engine is cold. On summer this is no so much big deal, becouse engine gets really fast to this temperature.
But winter, it was -10C (14F) this morning, and it took about 10min drive to get rid of the symptoms.
All the problems wanish when engine temp is above 50C (122F)
My educated quess is the temp sensor.
And thank you Macster, I have all ready ordered Durametric.
When it arrives, I will check the sensors.
Ashamed of myself? For using my car? I don't know what some of y'all think happens to these cars when the outside temperature drops below 50 degrees, but it's simply not true.
Also, a "cold start" isn't describing the act of firing the car up at -16 degrees, like I did just this morning.
Ok,
So I got the Durametric and tested the sensors this morning.
Maf is ok, values at idle about 37kg/s (if iremember the unit correctly)
ECTS was 7Celsius of from ambient, but I dont think this if causing the broblem
IATS was 12Celsius of
Only one fault code, "injector 1 open circuit" reset it and it did not come back.
I think I will try the injector cleaner that Pac996 suggested and see if that helps
I hope the engine looses its chill towards running in the cold. Even if a little water or gunk ends up in an injector it can freeze things up which might be whats happened. Even the cleaner fluids don't make injectors all the way clean. There are different varietys of injectors and some of them have so many tiny passages I could swear they are meant to foul up. I don't think ethanol helps matters with the water the alcohol can hold which makes me think of the fuel like a dakari cocktail for the car going through the fuel lines
ok, just got mine FIXED
List of things that I did
- Put back the loose injector #1 wire... (yep, my foult)
- Put some connector cleaner and oil to engine harness plugs. (that attaches to frame harness)
- Take out and cleaned the oilfillertube, seems that it had a small leak in o-ring that is on the block side. Put some engine silicon on the o-ring. (did not have new o-ring) (This one was pain in the a** to do)
- Put some engine silicon on the throttlebody seal.
- Cleaned the maf with some electrical cleaner
I used the durametric to find out the problem. There are dme setpoints in the servicemanual, and some info what could be wrong if the values are wrong.
Specs can be found on Group 0 diagnosis to 45, on the servicemanual.
