Matthew Currie
NAXJA Member #760
- Location
- Vermont, land of big clay
I'm away from my Jeep for the next week or so, doing Alzheimer-babysitting duty with a crappy dialup connection. But anyway, I figured I'd put out a small problem and see if the gurus can come up with suggestions.
The vehicle is a 95 4.0, 5 speed. It has 258K miles on it. It has good power, leaks all fluids prodigiously, but otherwise runs well. Plugs are at least fair, cap and rotor and wires old but not conspicuously faulty. No flashes in the dark.Timing chain appears not to be too slack (informal engine turning test). Vacuum is rock steady and normal. Fuel pressure is normal, stays up even when revved. Injectors all test as at least functional using an injector tester and gauge. They all drop pressure by the same amount, and seem to snap shut without dribbling. MAP sensor was replaced about 50 K miles ago. All other sensors are original, including O2. It isn't overheating. Throttle body hasn't been cleaned recently but looks good. Virtually no blowby either. It could probably use a new air cleaner, but it doesn't look bad. It has never sent out a code, but I know the system is working, because it threw a code when I purposely pulled off an injector plug.
One thing I have not done in a long time is to check the IAC valve for carbon. But idle speed is fine.
But when I idle for any length of time, it starts running a little rough, and then spits and misses when I take off. It revs fine, and once it clears its throat it seems all right again. I cleaned the plugs and a fiddled with connectors and it seemed to help a little, but I didn't have time to give it a good test, and suspect that's not really the problem. Reiterating, the thing does not miss or sputter under load, hill climbing, etc., and revs freely without any sign of problems. Fuel pressure stays up even at high rpms, vacuum recovers nicely and never wobbles.
Any guesses? I can't test hypotheses for the next week ro so, but will welcome any suggestions.
The vehicle is a 95 4.0, 5 speed. It has 258K miles on it. It has good power, leaks all fluids prodigiously, but otherwise runs well. Plugs are at least fair, cap and rotor and wires old but not conspicuously faulty. No flashes in the dark.Timing chain appears not to be too slack (informal engine turning test). Vacuum is rock steady and normal. Fuel pressure is normal, stays up even when revved. Injectors all test as at least functional using an injector tester and gauge. They all drop pressure by the same amount, and seem to snap shut without dribbling. MAP sensor was replaced about 50 K miles ago. All other sensors are original, including O2. It isn't overheating. Throttle body hasn't been cleaned recently but looks good. Virtually no blowby either. It could probably use a new air cleaner, but it doesn't look bad. It has never sent out a code, but I know the system is working, because it threw a code when I purposely pulled off an injector plug.
One thing I have not done in a long time is to check the IAC valve for carbon. But idle speed is fine.
But when I idle for any length of time, it starts running a little rough, and then spits and misses when I take off. It revs fine, and once it clears its throat it seems all right again. I cleaned the plugs and a fiddled with connectors and it seemed to help a little, but I didn't have time to give it a good test, and suspect that's not really the problem. Reiterating, the thing does not miss or sputter under load, hill climbing, etc., and revs freely without any sign of problems. Fuel pressure stays up even at high rpms, vacuum recovers nicely and never wobbles.
Any guesses? I can't test hypotheses for the next week ro so, but will welcome any suggestions.
