98 Grand 4.0...jeep idles rough, stalls out, run rough at low speed...runs good at 65 to 70 mph.. have changed plugs, wires, distributor cap, and rotor.and new battery. No water in oil..no sign of smoke out of exhaust...also used fuel injection cleaner..Also, there is no check engine lite coming on. Jeep has 138.000 miles
Just bought the jeep..test drove it run fine..Bought, it drove it less than 10 miles to get gas...started jeep back up to leave the station and started running rough, drove home 3 hours, on interstate at 65 to 70 and run fine...but slow down or stop, would run rough and die.
Could it be a map senor, or some other sensor? Will try any suggestion or advice.
We own two other jeeps...1994 Cherokee with 242,000 and is a work horse, 5 spd. manual.
2000 Cherokee Sport Classic with l50,000 and no problems with it, 5 spd. manual.
This is our first Grand Cherokee, automatic.

 

Sounds like the Idle Air Control motor might be failing. They tend to act up once the engine reaches operating temp. The engine will run fine if you keep your foot on the pedal, but will die when you take it off of the pedal. NAPA has the improved designed IAC motor for around 75 bucks. Two Torx T-20 screws hold it on the side of the throttlebody. Don't waste your time removing it and cleaning it, just replace it.

 

You posted that your problem come after getting fuel at gas station. Any chance that you put diesel in tank?. If not then maybe you have "bad gas". Some gas station add water to fuel. Burn as much as you can and buy gas from different station. You my want to put some fuel addictive.

 

The diesel nozzle won't fit in the unleaded filler neck.

 

Sorry, never try that. I heard of people putting diesel by mistake.

 

I had posted my problem earlier about my GC rough idle and dies out and runs and smooths out at high speed...I replaced plugs, wires, distributor cap and rotor. Also put sea foam in gas to my sure it was not bad gas..have not tried the air idle control valve yet..But after checking the new plugs and wires..I found that plug 5 and 6 are not firing, both plugs are wet of gas. other plugs 1,2,3,4, are firing properly. Need help..where do I go from here..As I said I just bought the Jeep and it was running fine till I stopped about 10 miles from dealer and put gas in it and started back up and then had rough idle and miss for a 3 hour trip back to my house. Interstate driving at 65 and 70 ran fine. Could it be a igition problem? or could I have a blow engine? There is sign of smoke, water or anything coming out of the exhaust and there is no water in the oil..

 

mine does the same thing i have a 97 zj 4.0 hopefully somebody knows

 

I would check the compression. It should be 120 to 150 psi. Allowed variation is 30psi. The other option to check is to : while idle engine, spray carburetor cleaner around 5th and 6th cylinder in intac manifold. You my have vacuum leak due bad manifold gasket. If engine rpm rise up while spraying, then replace manifold gasket. Check for air bubble in radiator. That will indicate warp head where some compression is going into water passage. You could have burn valves too. Disconnect the "blow by" valve (top of valve cover plastic plug on rubber seal with rubber house going to air intake). If you can, compare to other jeep. There is allays some "blow by" but is mild.