Hi, all. my '93 4.2 is experiencing a set of symptions for which I'm trying to find correlation. Any assistance is much appreciated.
thanks for your advice!
- Symptom 1: On cold start, the engine surges to 1000RPM, drops to ~200RPM and almost stalls, surges to about 1200RPM, and then evens out. This has happened to some degree since I got the truck, but recently the delta has grown so that it's closer to stalling and revving higher.
- Symptom 2: On warm start, the engine will start, but within 5 seconds die. Subsequent attempts to start will be met with, at best, a few seconds of stumbling. When it cools sufficiently symptom 2 goes away. This started about the same time as symptom 1.
- Symptom 3: Rough idle. At stop lights the whole truck rocks, and if I use light braking I can feel the engine pulsing through the drivetrain. The latter leads me to believe it's not motor mounts.
- I replaced the alternator with a rebuilt Magnet Marelli 100A to fix a wandering voltage problem. That did not affect any of the above symptoms.
- I replaced the temperature sensor hoping that was the problem for symptom 2. No dice because it did it again.
- Replace wires, plugs, rotor, cap, or any fuel system stuff.
- Check that the ECU is reading the temperature sensor correctly. (I don't know how to check that)
thanks for your advice!