97 Cherokee Issues

[MikeJeep]

I have a 97 Cherokee 4WD 4.0l I6. Lately it has been starting fine here and there. Other times, it will not fire up at all. The motor will turn over, but will not fire up without having the gas pedal fully depressed. When it does fire up, in that case, it runs very rough. when i revv up the motor, it seems to sputter and stall first and then it revs up. Sounds like crap! Sometimes it will stay idling rough or just shut off. Also, When I rev up the motor, Black smoke (looks like rich fuel smoke) comes out of the exhaust. I have replaced the MAP sensor and will be changing the O2 sensors today. Just wondering what else it could be????? Also, I can get it to drive sometimes, but only a very short distance before it dies. Any advice will be helpful. I am very frustrated!

[AlohaBra]

On a 97, with fuel injection, you should never floor the accelerator.
More likely, you have lost fuel pressure while sitting. Turn the key on without cranking and wait for the fuel rail to pressurize. Turn key off and then try and start. Otherwise, try the crank position sensor. I presume you have looked at plugs and distributor cap and rotor.

[fredjacksonsan]

I've read here that a bad crank position sensor can cause hard starting.

[MikeJeep]

For those of you interested, I tried the following advice and it seemed to have worked!


One thing here that has worked in the past (really for no good reason)...

1. Disco your batt.
2. Then unplug ALL of the connectors at the PCM (it's an HO so the PCM is "outside" underhood...)
3. Using soft copper wire (solid like in-wall phone ~22-24AWG) with the insulation removed ...
4. Poke/probe each plug hole before reconnecting the PCM then the battery....
5. This has been known to dislodge contamination and/or just make the damn thing run better...

Sometimes I forget that the PCM and it's many connections are both out there getting all nasty - it only takes a little som'pin-sump'in to keep a contact from behaving. Un-mating/re-mating the connectors can often do the deed; adding the "probing" seems to help a bit more (Hey, it works for space aliens)... just another thought