88 cherokee idle issue

[cherokeewarrior(andson)]

I have a 1988 cherokee, 4.0 inline 6. It intermittently will not idle, you can not keep it going by depressing the accelerator, it just dies. It will start back immediately but as stated will knock off right away or idle for several minutes before dying. I have changed the fuel filter, fuel pressure regulator on the injection line, cleaned the rotor button and rotor cap, sanded (lightly) the hub directly below the rotor button. Do coils fail intermittently? What else should I be looking at? Is it possible the fuel pump is gone, or do I have an electrical issue and how can I be certain I am addressing the right solution? Thanks for any help on this.

 

[SteelHeadz]

Try cleaning the IAC and the throttle body from carbon build up. I have not seen a coil fail intermittently. I've seen it fail after engine warm up and works after it's cooled down. If you have a fuel pressure tester, you can easily eliminate the question with the fuel pump. Clean the IAC and the T. body first and see what happens..

 

[cherokeewarrior(andson)]

IAC? What is that acronym?
thanks

 

[SteelHeadz]

IAC? What is that acronym?
thanks

Intake Air Control Solenoid.

 

[cherokeewarrior(andson)]

Thanks for the help. (andson) expresses his gratitude also, the jeep now idles (roughly). We cleaned the TBI as recommended and that seems to have done the trick. We also changed the plugs and wires to attempt to smooth the idle some, the old plugs had heavy black carbon (?) deposits. The jeep idles as stated slightly rough, and blows black smoke when revved up, at idle it emits a small amount of black smoke. Any further suggestions for this? Timing is between 5 to 8 degrees, does not repeat in exactly the same place each time.
.

 

[SteelHeadz]

Did you remove the Throttle body off the intake and remove the IAC motor to REALLY clean it?. If you found a heavy carbon build up on the plugs then it would be safe to assume that it's going to be the same on the Valves. The IAC motor has a plunger on the end of it's pintle, make sure that the seat on the T.Body is clean and likewise on the plunger. check the pintle for carbon build up as well. If the rod can't freely move in and out as the IAC motor wants to make adjustments for the air and fuel stoichiometric ratio then the idle will suffer..The black smoke could be from the solvent used to clean the T.Body if you didn't remove it from the intake. It will eventually clean out as it heats up.

 

[cherokeewarrior(andson)]

Replaced the IAC, removed TBI and cleaned, replaced TBI gasket. Idle smooth, acceleration smooth, no missing or hesitation. Thanks for the help, you guys are agreat resource for us novice jeepsters. Keep up the good work.