2001 Jeep Grand Cherokee Need Help

I have a 2001 Jeep Grand Cherokee I cant get the engine light to stay off. It kept saying misfire 234 and 5 I have replaced coil pack, plugs , had the head taken to a head shop, replaced the gas cap and fuel injectors. light went off for a couple days and keeps coming on Jeep is getting good gas mileage and is not shaking when driving it. Please any help would be appreciated.

Unfortunately…the CEL system is very weak when it comes to troubleshooting. It was designed to alert you to a problem but that’s about it. A very accomplished (experienced) mechanic can often find the real problem quickly but on occasion…they are as stumped as anyone else. As an example, my brother had a persistent CEL that he could not get to go out even after having it worked on by a couple of dealerships and an independent mechanic. I looked at the fault codes and determined it had something to do with oxygen to the engine. I pulled the air filter and the light went out in a few miles of driving. I installed a new air filter and cleared the fault codes. The light has not been back on since. I suggest you get an experienced mechanic to take a close look at your Jeep.

You can’t have that many cylinders misfiring and still have a running engine. Take it to an AutoZone or other parts house that will read the codes for free and get the actual code or codes. They will be in a format P0xxx. Post those codes here, the actual code, not what someone else says they mean.

Also tell us which engine you have, inline 6, V6 or V8.

Good advice above. One simple thing you might do is idle the engine in a dark garage, at night with no lights on for example, with adequate ventilation of course. Do you see any sparks or anything else unusual lighting up in the engine compartment?

Very good post for TSB on carboned exhaust valves causing multiple misfire codes on the 4.0

Sounds like a bad ECM throwing erroneous codes…If emissions testing is not an issue, I would ignore the CEL…

I think there’s some info missing . . .

In my opinion, it’s highly unlikely to have that many misfire codes, but the engine is running great

I bet if any of us actually were to drive the vehicle, we might feel the miss

Perhaps OP has just gotten used to the engine behavior

After all, we all get used to our worn out shocks. But when somebody else drives the car, they can immediately tell something isn’t right

One more thing to consider . . . OP said the car doesn’t shake when driving it

Okay, that’s fine. But . . . I’ve worked on several cars that had a definite miss at idle, yet if you drove it, it didn’t feel that bad

I wish I could explain it better

"had the head taken to a head shop"
Tina, can you describe in the best detail you can what this statement means?

The reason I ask is that clarification of this statement could have a very large effect on determining what’s causing the Check Engine Light.

I should also add that, as Missileman already suggested, the CEL only warns the driver that there’s a problem. It does suggest areas where the problem might be found with diagnosis, but it was never intended to diagnose problems. It’s triggered by the OnBoard Diagnostic system, but the system is designed only to monitor those things that might if malfunctioning cause excessive emissions and notify the owner that a problem exists. Inclusive of these things are numerous operating things, but the system is only a “red flag”, not really intended as a diagnostic tool for the owner. Mechanics find them useful because they can by their nature store and allow direct monitoring of the readings from numerous sensors that a mechanic can use to help find the possible faults.

Tell us more about the “head shop”.

Head shop means that I had the head removed and taken to a place that replaces valves and gaskets and whatever else they do cost almost $400 The dealer said it was the head. auto zone says it is misfiring on cylinders 2,3,4,5 it wont pass emissions and it does run fine had 3 mechanics look at it and they are stumped even gas mileage is around 18 per gallon. I know I don’t know a lot but have mechanic friends and all have checked it with the code and all say its misfiring but clearing its not because of replacing everything.

engine is inline 6

Has anyone checked for a stretched timing chain?


No one has checked anything about the timing I wrote down all your suggestions and I am taking them to the mechanic if one of them work I will let you know Thank you for the time of trying to help me

If a vacuum leak check hasn’t been done yet I suggest doing that. Also check the EGR vavle and replacing the the crank position sensor may solve the issue. This kind of trouble can come from a number of things, some of which you have already tried without success.

Can you read the codes and post back the exact codes you’re getting?

When AutoZone read the codes, they should have entered the codes into the computer in the store and it would give you a printout of the code and what it means. The actual code will be at the top of the printout. If you have these printouts, please look at the top of each one and give us the actual code, not the interpretation of the counter guy. If you don;t have the codes, or the counter guy didn’t print them, go back and have them read the codes again and give you the printouts or at least copy down the actual codes and post them here.

A misfire code does not actually mean there was a misfire. It means the voltage measured on the primary coils during the firing of the coils was not the same as other cylinders, and there can be a number of reasons for that. The voltage needed to cause an arc at the tip of the sparkplug varies by compression, fuel/air mix, plug gap, resistance from the secondary of the coil to the plug and other factors.

If your mechanic has an old fashioned oscilloscope, he could hook it up to the hot primary lead of each coil in succession and see the actual voltage spike on each coil and that may help him find the problem. It is possible that the sense lead from the coils to the computer have been damaged or the coils have different manufacturers. All the coils should match pretty closely, as should the plugs.