88 intermittent misses / dies

[mpsvn]

88 Cherokee with intermittent miss / sometimes dies for last 2 years.

misses and dies at idle.
misses at hiway speed, but usually recovers
sometimes jumps up to over 3K at idle--turning off engine and restarting a couple of times fixes that.
may run for a month with no problems, then runs bad every day -- or until I get it to a shop --then it runs fine.


Sometimes it acts like someone just turned off the ignition.


TODAY -- it died several times (felt like turning the key off) and would not restart at first--after 5 minutes restatred. During first restart attempt, it felt like was out of gas (i.e. "almost started but died), but it had fuel pressure.

When it finally did restart the Transmission no longer will shift into overdrive. ( I went up to about 65).



what has been done.
TPS replaced 3 times.
Crankshaft position sensor replaced.
MAP replaced.
Fuel pump, filter, hoses replaced.
Ignition module replaced.
Distributor cap, rotor, plugs, wires, air filter, replaced.
Wire harness on top of engine "cleaned up" and all connections soldered.
ECU connections cleaned up.
Idle stepper motor replaced.


In general, after it is in the shop, it runs fine for 1 month, then the problem gradually comes back. (Also, they never find anything specific, because it is intermittent).

1) What is the next suggestion? (seems like the transmission not shifting into overdrive ought to mean something--assuming it's related).

2) Where can I find a corrrect wiring diagram for this? The Chilton's manual isn't correct & the normal manual supply places says it's too old. someone must have something I can copy.

It's been a great car until this--230K miles -- no problems.

Thanks, Mike N.

[Ironic]

Had same syptoms you described, the tps fixed mine, but through my search for a fix found a ton of suggestions. just to rule one thing out- make sure your cruise control switch is off. As for the wiring diagram- http://209.238.200.129/gw/elec/cherokee/91076b23.pdf
Intermittant problems I usually find is the fault of bad electrical connections- would follow the leads from the tps, who knows- might get lucky- good luck bro.

[mpsvn]

Thanks -- I stumbled on the solution completely by accident, but don't know why it is working.

I found a ballast resistor on the LH fendor. Terminals looked terrible. While the engine was running I disconnected it. The engine missed, stumbled, and then eventually died.

I cleaned up the terminals, reconnected and have had no problems since. The schematics for the 88 (including the one you sent to me--thanks for this site--it's great) don't seem to show a ballast resistor anywhere--also my connector on the computer is different. (has 4 rows of 16--only the inside 2 rows are used). I rechecked the year,etc and it is definitely an 88. Guess I'll have to buzz out some wires and see where they go.

I found schematic for carburetor model that shows ballast feeding the coil. I also found schematic for 92 model that shows a ballast feeding the fuel pump. Either one of those could cause the problem I had.

Did I miss the ballast resistor on the schematic somewhere -- it's about 5 ohm.

Thanks for the response. I hadn't thought about the cruise control and it was ON. thanks for the tip.

Mike N.

Originally Posted by Ironic

Had same syptoms you described, the tps fixed mine, but through my search for a fix found a ton of suggestions. just to rule one thing out- make sure your cruise control switch is off. As for the wiring diagram- http://209.238.200.129/gw/elec/cherokee/91076b23.pdf
Intermittant problems I usually find is the fault of bad electrical connections- would follow the leads from the tps, who knows- might get lucky- good luck bro.

[BCBlues]

That ballast resistor that you found controls the fuel pump at startup and idle. It is connect to the starter relay.

[wazoo84stang]

i had this same problem and it was the wiring going from the tranny into the firewall. you just need to put new wires in. it should solve your problem instantly.

[Saudade]

I checked the diagram on the link above and it seems very different from the one in my Haynes manual. Mine clearly shows the ballast resistor.

[mpsvn]

Thanks all of you very much -- I found the problem and forgot to post it.

1) The connection to the ballast resistor was loose and the terminal corroded.

2) The wire to the ballast resistor was very tight--every time the engine vibrated or you went around a corner it would stretch--that along with the lose and correded terminal cut off the fuel momentarily.

I'm actually surprised that a momentary glitch to the fuel pump can seem like an engine miss -- I would have expected it more to act like it was running out of gas.

I extended the wires, cleaned and soldered them to the ballast resistor terminal. So far (about 2 months) problem has not re-occurred.

thanks again, Mike N.