Thread: RE: Stalling @ startup (cold only)

Hello all…
I have small issue maybe someone can help with..
2003 Grand Prix GT 90,000 mi. 3.8L (L36)
On cold start: The motor nearly stalls and then picks itself back up. The RPM’s drops to about 400 -> 500 then jumps suddenly to normal warm up RPM (about 1200 to 1500). I’ve never noticed this before this week.
I purchased: ScanXL Pro with GM enhanced plugin, performed a data record driving around for about 15 mi. I noticed from the data that the engine never went into “open loop” when cold (maybe 40 to 50 degree outside temp is warm for open loop? Maybe someone has some input on this?).
Additionally, I’m reading only two “02” sensors, I though there were three on this car.
I’m thinking one 02 sensor may be the culprit, it reads lean and rich then back to lean frequently.
Thanks again in advance for any help on this.

Regards/Marc

Originally Posted by BillBoost37

Marc,

You only have two O2 sensors, you are seeing the correct number. The way you describe the B1 Sensor is it's normal operation. It should toggle rich/lean fairly quickly.

On the cold starts, I'd pull the TB and clean it and the MAF/IAC. You'll be surprised how much that helps things.

BillBoost,

Thanks much for the info, you cleared up my concerns about the 02 sensor... I'll go ahead and pull the Throttle Body clean the MAF/IAC as you recommend, I have read elsewhere this is recommended to clear up minor issues...

Thanks again for your reply..

Best regards/Marc

My car does that from time to time... I know I have a bad MAF(too cheap to buy a new one), so like Bill said, get some MAF Sensor cleaner and clean it. Cleaning the throtlebody can also help with some ideling issues.