Cherokee dies

[Edbrooks]

OK, I've solved some of the problem with my 88 Cherokee Pioneer. Smoother idle. Most of the time.

Still stalls. Suddely, for no reason I can figure. Frequently I can make it stall by tapping the gas pedal quickly while it is moving very slowly. Were it with a carb, I'd think flooding.

Just put new injectors in it couple of days ago, as one was indeed leaking a little, so decided to put them all in. That smoothed the idle.

But ... the stalls are making it an unreliable vehicle. Most of the time it will restart fairly easily, but not always. It does, though, restart eventually, after several tries. May act like it's trying to start but it doesn't make it. Stalls seem to have no external clue - sometimes when I 'goose' the pedal, other times when I let off on it, and sometimes when it is just cruising along, but always at relatively slow speeds, under 20 mph. Never at highway speeds.

The book and a pro mechanic both say "change the CPS." Yet when it dies, I take a resistance reading of the CPS and it is exactly where it should be. I even put a VTVM on the output of the CPS and got a steady signal, but of course the engine was running smoothly at the time.

Several years ago I replaced the sensor in the distributor. This time I unplugged that sensor and drove it a ways, and it stalled just the same.

Have replaced the O2 sensor, and adjusted/checked the TPS. Checked the MAT and MAP sensors, and both read as they should. Checked the EGR system. Fine working order.

Thoughts?

Ed

[cusz28]

Hey dude, my 87 XJ w/the 4.0 does the same thing. But, I might have a very good answer. I bought my jeep not to long ago, and set out to fix the problems that it had. After awhile of scrathing my head, i noticed that my TPS sensor (throttle position sensor) was installed backwards. after is reinstalled it the right way, the engine responded immediatly with a 200% better running idle and throttle response. Let me guess, you jeep has a problem maintaining a stable idle, if any, around 500 rpm or less, it dies when you give it too much gas (doesn't matter if it's in gear or not), and it has problems driving at slow speeds where it may literaly bounce off the 0 rpm line, then recover. this is what is happening to me. I'm probably going to replace the TPS sensor next chance I get, and I can almost, I say almost because I'm not for sure, gaurantee you a better running jeep. Now, by the slim chance that you have replaced the sensor and it is still running like pure crap, then i'd like to discuss options.

[89ltd]

you said you checked the egr valve and it is working, but it may be opening to soon, that would give you hesitation at low rpms, try dissconnecting the egr vacum and plug the hose to see if it runs better.

[xj31]

Originally Posted by 89ltd

you said you checked the egr valve and it is working, but it may be opening to soon, that would give you hesitation at low rpms, try dissconnecting the egr vacum and plug the hose to see if it runs better.

What he said

[cusz28]

Originally Posted by 89ltd

you said you checked the egr valve and it is working, but it may be opening to soon, that would give you hesitation at low rpms, try dissconnecting the egr vacum and plug the hose to see if it runs better.

I will definitley try that tommorrow. I've currently made a list of possibles causes that includes the EGR valve, but I haven't gotten to that part yet. I guess that checking it has moved to the top of my list. thx~

[SteveB05]

If you don't mind me asking, how are you checking the sensors...specifically the TPS? A scope is the best way. Multi-meters, especially digital can't always react quick enough.

[cusz28]

I've tried the EGR thing, and it didn't work. It still ran like crap afterward. As with the TPS sensor, I really haven't gotten to it yet, but I do know that when I got the jeep, the TPS was missaligned...majorly, and when I took it out and reinstalled it it ran PERFECT. I know my jeep has ALOT of miles (232,000), but it was able to rip the tires loose like instantly, then it returned to crap mode. Crap mode intales really low rough idle, bogging when given gas, dieing when given too much. and pretty crappy acceleration. Oh, and like no torque.

[bulletpc]

you might want to check your intake\exhaust manifold gasket.I have changed the one on my 89 pioneer 2 times same symptoms.