ek245
New member
I'm trying to track down an intermittent stalling/near-stalling issue with my 2004 Pontiac Grand Prix GT. It's the naturally aspirated 3.8L Series III 3800 (non-supercharged) with about 245,000 miles.
The car has only completely stalled once. The other times, it acts like it's about to stall but catches itself and recovers.
When the problem occurs, it can happen both while maintaining a steady speed and while accelerating. The tachometer drops down to around 1,000 RPM, and then the engine catches itself and comes back up.
The one time it actually stalled, the engine cut off completely and the tachometer dropped straight to 0 RPM.
There isn't much warning beforehand. It doesn't seem to gradually lose power; it feels more like the engine suddenly loses RPM and then either recovers or, in the one instance, completely dies.
I've had the same problem several times now.
The first time, I brought it to a shop and they had the car for 11 days. They weren't able to reproduce the problem. They did some sensor cleaning, but apparently didn't find a definite cause.
I got the car back and had it for about 12 days before the same issue happened again, so I brought it back to the same shop. They aren't charging me for the diagnostic this time because it's the same issue returning shortly after the first visit.
The only trouble codes I've personally seen are:
I'm trying to figure out where I should have the shop focus their diagnosis. Since the engine RPM sometimes drops dramatically but recovers, and the one time it actually stalled the tach dropped straight to 0, does this point toward a possible intermittent loss of the crankshaft position/RPM signal?
Could the P0107 be related to the near-stalling, and is simply cleaning the MAP sensor enough to rule anything out, or should the MAP circuit, wiring, and connector be tested?
I'm not looking to just throw parts at it, especially since the shop hasn't been able to reproduce the problem.
What would you guys check/test first on a 3800 with these symptoms?
Thanks!
The car has only completely stalled once. The other times, it acts like it's about to stall but catches itself and recovers.
When the problem occurs, it can happen both while maintaining a steady speed and while accelerating. The tachometer drops down to around 1,000 RPM, and then the engine catches itself and comes back up.
The one time it actually stalled, the engine cut off completely and the tachometer dropped straight to 0 RPM.
There isn't much warning beforehand. It doesn't seem to gradually lose power; it feels more like the engine suddenly loses RPM and then either recovers or, in the one instance, completely dies.
I've had the same problem several times now.
The first time, I brought it to a shop and they had the car for 11 days. They weren't able to reproduce the problem. They did some sensor cleaning, but apparently didn't find a definite cause.
I got the car back and had it for about 12 days before the same issue happened again, so I brought it back to the same shop. They aren't charging me for the diagnostic this time because it's the same issue returning shortly after the first visit.
The only trouble codes I've personally seen are:
- P0107 — MAP sensor circuit low input
- P0420 — Catalyst system efficiency below threshold
I'm trying to figure out where I should have the shop focus their diagnosis. Since the engine RPM sometimes drops dramatically but recovers, and the one time it actually stalled the tach dropped straight to 0, does this point toward a possible intermittent loss of the crankshaft position/RPM signal?
Could the P0107 be related to the near-stalling, and is simply cleaning the MAP sensor enough to rule anything out, or should the MAP circuit, wiring, and connector be tested?
I'm not looking to just throw parts at it, especially since the shop hasn't been able to reproduce the problem.
What would you guys check/test first on a 3800 with these symptoms?
Thanks!