Mon, 25 Jan 2010
Car Engine Advice Sought
I've been having intermittent problems with my car that have now stumped two mechanics, so I'm turning to the Internet for advice. I have a 1996 Jeep Grand Cherokee, with Selec-Track four-wheel-drive and a 6 cylinder engine.
The problem I'm having is that the engine will sometimes just stall (the motive power goes away and the engine RPMs drop to zero). It only seems to happen right after starting the car (so the engine hasn't warmed up yet), and it's much more common in wet weather (rain, snow, heavy fog). Often times, I can feel the engine losing power and can prevent a stall by stepping on the gas pedal. If the engine actually stalls, I have to wait at least a minute to restart it; if I try restarting it immediately, I hear the chug-chug-chug of the starter, but the engine won't start running.
I've had a few times when the stalling seemed to hit as I was braking, just as the automatic transmission was downshifting from second to first gear. I've had the car sall at times apparently unrelated to shifting, though.
This morning, it was particularly bad. I barely got out of the parking lot at home (after several stop/wait/restart cycles) before the engine stopped being useful--it would only run for 30-45 seconds before stalling, and I couldn't prevent the stall. I had the car towed to a mechanic, but by the time they took a look at it, the engine started and ran normally. They couldn't find anything wrong with the engine, and there were no codes from the onboard diagnostics.
The coolant system has a slow leak (my regular mechanic tracked it to the water pump, I think), but I've had that for over a year now and I doubt it's related. In the time since the problem first manifested, I've had a system tune-up (including replacing the spark plug wiring, apparently a common contributor to problems such as these), had the oil changed, had the transmission fluid changed, and had a (presumably unrelated) badly-leaking coolant hose replaced.
Any suggestions on what to look for to fix this will be gladly accepted. I'll be cross-posting this to several social media sites; responses there are fine, or just send an email to email@example.com
Update 2010-01-02: I've gotten a number of suggestions for problem areas that could be causing this problem. The most-suggested item was the fuel filter, which I haven't replaced since I got the car five years ago, so I'm taking care of that to start with. I'll see how well the car behaves with a new filter. Other suggestions have included the idle valve, O2 sensor, or fuel pump. If replacing the fuel filter doesn't work, I'll check out some of the other possibilities.