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Jeep Cherokee Poor Idle, Sputters

Q. 1993 Jeep Cherokee Laredo. Just had my A/C recharged and in this AZ heat it like winning a lottery. Once I left the garage and did some errands the car idling started to jump and hesitate. Left my Jeep sit over night and tried to start it again, the idling is rough, it runs as if the timing is off, missing fuel and even no spark.

Jeep Cherokee Poor Idle, Sputters

I replaced the fuel filter and plugs, I started the Jeep and it seemed to be fine (hurray).

BUT! I took a small test drive and soon the loss of power, poor idling all came back again. Brought to my mechanic and after some testing it was supposedly a bad fuel pump, pumping at 20 psi. Replaced the fuel pump and the same problem is still there. Even seemed worse.

Mechanic did more testing, he replaces the plugs, which I had already done, and feels confident the problem is solved. Starting engine looked fine until I added a load on the Jeep by turning the A/C on and then trying to drive it out of the garage. Same problem.

Did my fuel pump need to be replaced??? We are now on day 5, my mechanic calls me to say for no apparent reason he started the Jeep and all seems fine. I am having a deja-vue but am not surprised.

I try this myself at the garage, and it took long cranks to start the engine. The longer it idles, the worse it gets. Engine seems to want to stall, engine hesitates when gas is applied. Needless to say I have taken the Jeep home and am trying to diagnose the problem myself with your help.

Reading all these Q & A's it seems it could be the Crankshaft Position Sensor or the ignition coil or???? Anything that will shed some light on this would be appreciated.

Now my 1993 Laredo 4.0 liter inline 6 still has bad idle, hesitates when accelerating for the past three weeks. I have replaced plugs, wires, rotor, distributor cap, fuel filter and fuel pump. Was receiving a code 12. After replacing all these parts, the engine would start and run rough. Now it won't start at all.

I replaced the whole distributor which includes a new Camshaft Position Sensor. I got the car started and now it won't start anymore. There is fuel in the system and also spark. I still have a code 12.

Any help would be appreciated.

A. There are many possibilities in this scenario but the indication that your fuel pressure was low enough to cause a mechanic to replace your fuel pump steers me towards the fuel pressure regulator.

A pinhole in the diaphragm of this component can cause all of the problems you have described here. If the hole is small enough I surmise it could be intermittent.

Recommend you pull the vacuum line off of the regulator and draw it down to 15 inches of vacuum and let it set for at least five minutes and note any vacuum loss. If it loses any vacuum at all in five minutes, the component is faulty and needs to be replaced.

Additional Information provided courtesy of ALLDATA

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© 2005 Vincent T. Ciulla

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