RENIX Dies Pulling From Stop - Long Post

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

check ur baterty somethign similar happened with my girlfriends 01 xj and it ended up being the battery

x2.

The synch sensor (Cam shaft position sensor) controls fuel injection, not spark advance, you mean the CPS, crankshaft position sensor, and the answer is maybe its the problem. Also look for a shorted wire that moves as the engine torques up into gear. Also check for a bad battery post, or connection.

Definately sounds like a mechanical wire connection problem in the igntion or ECU or ECU sensor and control circuits. Check the coil connections inside the ICM, under the coil, it is a simple snap clip contact that can corrode and loosen.

You mentioned grounds, but check the ground strap at the back of the valve cover to the firewall. Also look for wires against the exhaust manifold. The radio dropping out makes me think you've got an intermittent connection or short somewhere.

cygnus58 said:

electrical or mechanical EGR fault??

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I'd look into the EGR system as well.
it would be most apparent after the motor was warm and at idle, so it fits the problem description.

try pulling the vacuum line that goes to the EGR valve.

The radio part of the symptom doesn't add up.
According to a '88 wiring diagram, the radio uses a seperate part of the igntiton switch than the ignition coil.
They do share a common fuse link. (called "red or green")
If it were that, one would expect totally random stalling, not relative to starting from a stop.
From what I can see, the clutch switch only reports to the Cruise computer...Should prevent starting tho???
Clutch switch could be 2 parts, and I don't see second one.
If the radio problem is in fact related, my EGR suggestion is out.
In '91 the ASD relay (auto shut down) controls injectors and coil.
Still would not be related to pulling from a stop.
If I had a '90 schematic, I could see if Chrysler made other changes from '88 -'90 in that electrical area..
I think I remember reading that was a weird, transitionary year.

crankshaft positioning sensor.E-bay here you come!!:conceited

Going step by step, I would look for the following starting with the battery. Look for an internally loose battery post, in other words see if the battery post moves by pulling the battery clamp side to side, then check the battery clamps to see if one is loose. Next check the main hot wire running to the start / run relay near the battery, and the always hot wires leading from that same relay through the built in fuse links right at the relay. See if wiggling any of them makes the engine die. If non of them are suspect, I would suspect the ignition switch, and or wiring harness connectors at the ignition switch are on their way out.

Getting back to those fuse linked wires at the start/run relay near the battery, one feeds the +B latch relay, another feeds the fuel pump relay and the ECU directly. The other feeds the ignition switch.

As cygnus58 said, the radio consistently dying at the same time is your biggest clue where not to look!!!! It has to be between the ignition switch and the battery, or the battery and those fuse links to the fuel pump relay or the +B latch relay, but my first guess would be the ignition switch or the fuse link wires at the start /run relay.

The ignition switch is very to prone to fail on these!!!!! Especially at the overloaded brown wire that feeds the radio and A/C heat blower. They literally melt and burn out starting there until they finally die completely.

I wanted to follow up and close this one out. A couple of you guys had your logic right on. Last night I sat down with the Electrical FSM and went over the wiring. I came to the same conclusion you did, Ecomike. Had to be in the battery to start relay wire or the fuse link (or main ground cable).

Went out this afternoon and just turned on the radio (ACC on ig switch). Started wiggling wires and nothing would cut the radio out. I decided to do the same thing with the engine running. Started engine and started with the main ground cable (figured that was the other place it could be). No problems there. Put my thumb on the main supply from battery to start relay, pushed down, engine died. Started engine back up, did the same thing, engine died. Eureka! A 6 inch piece of number 8 wire and two ring terminals and it's all fixed. Fault only showed when a lot of current was flowing (engine running).

Thanks to all of you for the input. My first thoughts were ignition switch, but then I got distracted thinking it was a sensor. A little time with the wiring diagrams told me it couldn't be that. You guys who said the radio going dead was the key were right on.

don't overlook the motor mounts-- if they're worn you may be pulling on a connection when you load the engine. Have someone else set the parking brake and ease off the clutch as you inspect for movement

Glad to hear it.

Shorty - I was thinking the exact thing, it would pull a questionable connection VIA the starter.
And from a stop the engine would rock a little more eh?

Unless of course, you flat-shifted like I used to my '70 Swinger, it would rock lots more often..
I was young and dumb. but DAMN, muscle cars were fun!!.

cygnus58 said:

Glad to hear it.

Shorty - I was thinking the exact thing, it would pull a questionable connection VIA the starter.
And from a stop the engine would rock a little more eh?

yup!!:roll:


Unless of course, you flat-shifted like I used to my '70 Swinger, it would rock lots more often..
I was young and dumb. but DAMN, muscle cars were fun!!.

Click to expand...

Indeed!-- I never seemed to have a problem with that in my '66
Mustang though-- had a '71 Cleveland block that was 2" wider than the shock towers-- never moved an inch!!