oldradiostuff
NAXJA Forum User
- Location
- California
Hello and thank you all for an informative and helpful forum - I have learned a lot here, but I'm getting a little stumped right now. Long post warning:
I have a 1990 XJ, 4.0 engine, AX15 5 speed manual, NP231, A/C but no other luxury/power items, about 235,000 miles on it.
About 2 weeks ago it started occasionally "bucking" when pulling away from a stop. I could accelerate through it and put it down to a flat spot on the TPS, and decided it was probably time to put on the new TPS (OEM Mopar) that I had in a drawer.
Last week, on a couple of different occasions (had not swapped TPS yet), it died pulling away from a stop. And by died I mean just like I had turned the key off. In fact, it would shut the radio off momentarily, but after the engine was killed the radio would power back up. Every time it died, it would immediately start right back up and idle and run fine.
This past weekend the rain stopped long enough for me to install and adjust the new TPS - still the same thing. In fact, if I just let it sit and idle, it will occasionally shut down, usually after it is warm and with no predictable frequency. I let it run about 20 minutes last night and it would never die, today it died after about 10 min of idle, restarted and died again about 5 minutes later, then I couldn't get it to die again.
In addition to the TPS, I have tried swapping in new Fuel Pump Relay, new B+ latch relay, I jumpered the fuel pump ballast resistor, and today I put on a new CPS (what a joy of a job - once I figured out the correct sequence of wobbles and extensions it went pretty quick). After every change I've tested it and it continues to die the same way.
Several months back I cleaned up all the grounds and reconnected them (new battery cables also). This weekend I took most all the connectors apart and cleaned with DeOxit and reconnected them.
The only real consistency is it tends to do it just as I am engaging the clutch and pulling away from a stop (but not every time I do that). It doesn't lug or stumble like I was stalling the engine, it just shuts off.
I replaced the ignition switch and lock cylinder about two months ago, and I've gotten under there in the last few days and made sure everything is plugged in tightly and wiggled the rod to make sure it isn't shutting it down, it all seems good.
In my opinion one of the sensors is sending a death signal to the ECU to kill the engine, then when the engine dies it immediately resets the sensor - it is always easy to start and easy to restart after dying. When I think about what's going on as I pull out from a stop - the change in manifold vacuum points toward a MAP sensor maybe, and the advance of the spark points to the camshaft position sensor. The easy restart tends to point me away from a fuel pump or a coil.
I would appreciate any input. Is anyone seeing anything in the above that I'm obviously overlooking? Thanks in advance for any advice.
Dave
I have a 1990 XJ, 4.0 engine, AX15 5 speed manual, NP231, A/C but no other luxury/power items, about 235,000 miles on it.
About 2 weeks ago it started occasionally "bucking" when pulling away from a stop. I could accelerate through it and put it down to a flat spot on the TPS, and decided it was probably time to put on the new TPS (OEM Mopar) that I had in a drawer.
Last week, on a couple of different occasions (had not swapped TPS yet), it died pulling away from a stop. And by died I mean just like I had turned the key off. In fact, it would shut the radio off momentarily, but after the engine was killed the radio would power back up. Every time it died, it would immediately start right back up and idle and run fine.
This past weekend the rain stopped long enough for me to install and adjust the new TPS - still the same thing. In fact, if I just let it sit and idle, it will occasionally shut down, usually after it is warm and with no predictable frequency. I let it run about 20 minutes last night and it would never die, today it died after about 10 min of idle, restarted and died again about 5 minutes later, then I couldn't get it to die again.
In addition to the TPS, I have tried swapping in new Fuel Pump Relay, new B+ latch relay, I jumpered the fuel pump ballast resistor, and today I put on a new CPS (what a joy of a job - once I figured out the correct sequence of wobbles and extensions it went pretty quick). After every change I've tested it and it continues to die the same way.
Several months back I cleaned up all the grounds and reconnected them (new battery cables also). This weekend I took most all the connectors apart and cleaned with DeOxit and reconnected them.
The only real consistency is it tends to do it just as I am engaging the clutch and pulling away from a stop (but not every time I do that). It doesn't lug or stumble like I was stalling the engine, it just shuts off.
I replaced the ignition switch and lock cylinder about two months ago, and I've gotten under there in the last few days and made sure everything is plugged in tightly and wiggled the rod to make sure it isn't shutting it down, it all seems good.
In my opinion one of the sensors is sending a death signal to the ECU to kill the engine, then when the engine dies it immediately resets the sensor - it is always easy to start and easy to restart after dying. When I think about what's going on as I pull out from a stop - the change in manifold vacuum points toward a MAP sensor maybe, and the advance of the spark points to the camshaft position sensor. The easy restart tends to point me away from a fuel pump or a coil.
I would appreciate any input. Is anyone seeing anything in the above that I'm obviously overlooking? Thanks in advance for any advice.
Dave