Before I start if this has come up before please redirect me! I looked though but didn't see anything matching my issue.

Ok, so I have a 1993 Cherokee 4.0L 6cyl Base. It's also 4x4.

My issue is after start up it idles good for about a minute and a half, then I get a grinding noise followed by a rough idle and it feels like its going to stall, then it kicks back up and is fine. After driving it for a couple minutes its running good, but if it sits for about an half hour same thing happens.

This issue has caused It to stall twice right after startup. The grinding noise seems to be coming from the drivers side between the drivers seat area and engine which is followed by loss of power.

Also if it helps It has new alternator, ignition switch, Starter, plugs & wires, oil filter < (2 weeks ago), coolant flush < (a week ago). Cleaned out the throttle body 3 days ago and checked the TB cables which are good. It does have a slight oil leak, and coolant leak.

Could this Issue be related to a vacuum leak or possibly and bad/or going fuel filter or pump? There does seem to be a slight gas smell that can be smelled from inside the jeep. Don't see any leaking gas from the lines or tank.

I love fixing stuff, but hate when I cant find the Problem.

Any help would be great! Thanks.

 

i'm not sure what would cause a grinding noise. But two things to check would be possibly a sticking Idle Air Control valve. or potentially a failing oxygen sensor. These could both cause problems as that car goes from closed loop control(when you first start the car cold and it's going through its "warm up") to open loop control(usually once the oxygen sensors heaters have turned off and the car is above a preset temp) Again neither of these would make a grinding noise though. so either you have one big problem. or you have a rough running issue that's causing the engine to rattle a loose exhaust or something else.

 

Ok thanks I'll check those two things tomorrow after work. Turns out that the grinding noise was due to dirt mixed with some oil/grease at the back of the fan. I removed it and clean it up, now no more grinding noise.

Happened to notice it while replacing the coolant temperature sensor/switch. Guess I didn't clean under the hood as well as I thought. Haha.

 

Has this running issue been going on before the previously stated repairs?

 

XJred96, yeah it has been going on before the repairs. Only had the Jeep a little over a month now. The repairs were done since those parts were on their way out. The problem has been less noticeable the past few days after the new starter, and coolant flush + new coolant temp sensor/switch. Also gave it a good power wash. Wonder if a sensor or electrical connection has has gotten loose, dirty or needs to be replaced?

 

Rough idle causing the engine to shake on bad motor mounts?????

 

Thats what I was thinking as well when it came to the "grinding" noise. But it seems OP figured that out. Could still be motor mounts causing the engine to lean closer to one side of the shroud than the other? maybe?

If you have a fuel pressure tester you should do a leak down test. If you don't have a fuel pressure tester rent one. Hook the gauge up, start the jeep and check that it's between 45 and 55 psi. after it warms up. Turn the jeep off and monitor the fuel pressure over the next hour it shouldn't really drop more than 5 or 10 psi. if it does you have a leak somewhere; Injectors, Fuel pump check valve, fuel lines etc.

One other way to check and see if you are having a problem with fuel pressure drop is to do the Poor Mans Prime. Before attempting to start the car, turn the key to the on position for 5 or 6 seconds then turn the key to the off position and repeat this two or three times. After the final 5 or 6 second wait instead of turning the key off, start the Jeep. If it starts and runs well(when you know it would have normally started poorly) you know you need to start checking fuel delivery.

 

Motor mounts look good, but I'll try testing the fuel pressure. Just gotten so busy lately haven't even check the O2 Sensor. Thanks.

 

Post up a photo of these good looking motor mounts.

How's the trans mount also?

Are the big bolts going up into the adapter housing from the mount loose or missing? Seen that a lot.