Hello, I have a 1989 GTA 5.7 with a cold start hesitation and stumble problem but the car is fine when its warmed up or after 15 minutes of driving/idling. This problem happened 4 months ago and went away but now its back.

Here is the scenario, I will start the car and it will be fine but all sudden the RMP will be jumpy from 600-1200. As I start to pull away, the car will quit. As I am rolling at 30mph, I give it gas and the RMP will go down and I have no power like I am coasting. The car will quit if I dont put it in park at a complete stop but everything is fine once its warmed-up. All the problems gone.

It has a new fuel pump, fuel filter, new spark plugs/wires, fuel pump relay, ignition cap/rotor and EGR valve. Distributor and injectors are 6 months old. TPS and timing adjusted.

All thanks to those that can help.

 

Do you get any codes?
Can you get a Scan Tool on the car?

Have you eliminated the following:
Vacuum leaks
sticking throlttle linkage
Idle Air Control
EGR while in "open loop"
wires/plugs laying against exhaust, things like that
loose or damaged air duct b/w MAF and throttle body

Disconnect the MAF and see if problem is corrected

Check fuel pressure and vacuum while these conditions occur

I think its odd that it quits after 15 minutes of driving.
I would lean toward the MAF sensor as a related cause of the problem

 

A lot of good info above, you really need to check those before going any farther. I had a similar problem about a month ago. It would run terrible when cold, but as soon as it went into closed loop it would be fine. It ended up being my coolent temp. sensor.

 

I just acquired a scan tool and it produced no errors in closed loop/warm mode. The check Engine Light is not on either. I am letting the car cool off and will re-recan then. There are no vacuum leaks (I checked by squirting water around). The throttle linkage is not sticking. EGR valve is 4 months new. Wires/plugs in good condition and not leaning on exhaust. Air Ducts are good. My mechanic is puzzled and thinks its a MAF sensor. Its been de-screened 2 years ago and the wires are in good condition. I just cleaned around the area removing carbon deposits. I think I have it isolated to 3 sensors:

1. MAF Sensor
2. Coolant Temperature Sensor
3. Idle Air Control Sensor

I just purchased a coolant temp sensor from Autozone and will update on the problem either today or Sunday.
Thanks dudes!!!

 

the purge solenoid if not working properly can give you the same symptoms

 

I can't believe it! All the problems went away after installing a new Coolant Temp Sensor. I installed it last night and couldn't wait start it up this Sunday morning and the car behaved very well thereafter. No more hesitation, cutting out, backfiring and sputtering. I will keep the purge solenoid in mind, nevertheless. All is appreciated. Thanks to:
smithtc
Chet
jodylee8310@aol

 

Does the coolant temp sensor also control the fans? Both of mine stay on all the time the key is on now. They didn't do that until recently. I also have a cold / off-idle stumble. It isn't severe, kindof like a dead spot in a carbureted car. A slight hesitation and then it perks right up lasting only a split second.