: Slow start and stalling

12-09-09, 10:27 PM
97 deville deelegance 100,000mi, Service light on, extended crank time to start in the cold, rough idle for about a minute, really cold this week in CO and engine stalled two seperate times in same trip when coming to a stop (engine had already been running about 40min), put in N and starts right away. Pulled codes: pcm p0101-current, 0131-history, 0171-h, 0174-h, 0603-h, 1520-h, 1527-h, 1599-h; read many threads here about these codes and problems and realized that I needed to take it in. I talked with the service rep and explained all that had gone on and gave them the codes and a list of things (that I learned here) I thought needed to be done or checked, like clean MAF & TB, check crank sensors & fuel pressure reg & fuel psi & fuel rail etc.. I even said that maybe they could see if the HG is blown, I tried to be polite and not tell them how to do their job, I was just trying to help, anyway, that afternoon they told me that they pulled codes and saw that there were a lot and recommended replacing the MAF sensor and all three O2 sensors and clearing the codes to see if that would fix it, I asked if the fuel pressure was checked and the service rep wasn't sure; So I have two questions:
1-I brought it to a shop to get diagnosed, not to throw parts at it; do I need to go to a different shop?
2-based on my simptoms and codes, what are your thoughts?
Thanks, Juice
Background info: new fuel filter Jan 09, new spark plugs Jul 09.

12-10-09, 02:24 AM
P0101 - Mass Air Flow (MAF) Sensor Performance
P0131 - Heated Oxygen Sensor (HO2S) Circuit Low Voltage Bank 1 Sensor 1
P0171 - Fuel Trim System Lean Bank 1
P0174 - Fuel Trim System Lean Bank 2
P0603 - Control Module Long Term Memory Reset
P1520 - Transmission Range Switch Circuit
P1527 - Transmission Range to Pressure Switch Correlation
P1599 - Engine Stall or Near Stall Detected

Hmmm... I would start with troubleshooting the MAF. The O2 sensors are seeing too much oxygen in the exhaust so they think that there wasn't enough fuel added to burn it. That's why they think it has a lean condition. The causes would either be low fuel pressure, a vacuum leak or a sensor such as the MAF is not working efficiently. I would check for vacuum leaks first. Maybe that extra oxygen is getting in there after the sensor. The chart for P0101 says to especially check the MAF sensor seal, throttle body spacer, intake manifold, EGR valve plate and tubes, PCV system and the brake booster and hoses. I think that's pretty much all the places that a vacuum leak can occur. If there aren't any vacuum leaks and the fuel pressure is good, I would be willing to say that the MAF is probably bad.

You may have 1 O2 sensor going bad judging by the low voltage code, but I would just take it one step at a time.

12-10-09, 11:24 AM
Don't overlook the manifold overpressurization valve behind the P/S pump for a vacuum leak.

12-15-09, 07:08 AM
So I told the shop to just clean the MAF and check for vacuum leaks. They cleaned the MAF and didn't check for leaks but the service light is off and it seems to be running fine, although it is a lot warmer this week. Cross your fingers that it just needed a good cleaning. Thanks for your input. =)