RealDealBJJ

Hey Guys,

I just drove my 2000 jeep cherokee cross country to Georgia after California locked down the state. Anyway, the jeep made it the whole way with no real issues. There were a couple of times where it had a rough start but overall it drove fine. After I got here and the care sat for a whole day, the next day I started it up and it had a rough start and then the engine light came on blinking and then it would stop blinking and go solid, then after a minute or 2 it would go back to blinking again. I checked the codes and a P0301 code is popping indicating an Cylinder 1 misfire.

1st off, any suggestions for the best course of action would be great. Also, how dire of a situation would this be? Should I stop driving at all until I resolve this or can it handle some short trips?

Thanks for any tips and suggestions

Spencer_P

I wouldn't drive it. It's flashing for a reason, a flashing CEL means there is an active misfire. Check the simple stuff first, plugs, wires, cap, and rotor.

Ralph77

Yeah I would check into it before driving it.
So one day not to long ago I start the Jeep and drive to work.
Thought I felt an intermittent misfire. Same on the way home.
No CEL but plugged in the scanner to see if there were any pending codes.
There were none.
Next day start her up to go to work and all hell breaks loose.
CEL flashing on and off, sounds like it is running on 5 cylinders, etc.
Then the CEL goes from flashing to staying on in a matter of moments.
Shut it down real quick and walk to work. Only a 1/2 mile away. LOL.
Anyway plug the scanner back in when I get home after work and now I have a P0304.
Easiest thing first. Pull and replace the plug in cylinder #4.
Been fine since but as soon as the weather warms up going to swap them all out.

tjwalker

A flashing check engine light indicates a serious misfire, which if ignored....will destroy your catalytic converter. You need to get this resolved ASAP. It's a process of elimination. Here are a few things to get you started. Good luck and keep us updated!

1. Replace all plugs (properly gapped) or at the very least, swap the plug from cylinder #1 to a different cylinder and see if the misfire follows.
2. Swap the fuel injector from cylinder #1 to a different cylinder and see if the misfire follows
3. Test your coil rail.
4. Perform a compression test on all cylinders and see where cylinder #1 falls in relation to the others. The spec is 120-150 with no more than a 30 psi variation between cylinders. Don't ignore the possibility of an internal engine problem. They happen.

Good luck and keep us updated!

RealDealBJJ

ok, so I went bak out to the car and I cleaned the Idle Air control valve and then I started the Jeep. It doesnt seem to be misfiring anymore but the CEL is on(Not flashing). I'm going to check the plugs and the injectors tomorrow. When I switch them to another spot, how quickly would the code change?

Spencer_P

I wouldn't mess with the injectors because you could open a whole other can of worms. I'd start with plugs, then if nothing changes you can unplug one injector at a time. Start by replacing spark plug 1 with the correct champion plug. And maybe clear the code and go from there.

dave1123

It might be a good idea to change the plug boots and springs in the coil rail. They could be hardened and cracked after that long drive. Jeep recommends NGK ZFR5N plugs in the coil rail engines because of the waste spark system used on them. The older ones use Champion. Those engines fire the plugs every revolution, once on compression and once on exhaust. This is to reduce emissions and reduce ignition complexity by using 3 coils and PCM drivers instead of 6. 1&6 fire together, 5&2, 3&4. A sure sign of a shorted coil rail is misfires in these pairs together. Most common is 1&6.

DON'T EVER check the spark by pulling the rail and sticking only one plug in it and cranking it over. That 40K volts has to go somewhere and it will almost always short the coils inside the rail. Install all 6 and ground them all to check the spark.

Spencer_P

Yes my apologies, I'm not too fimilair with 97+, I'm just used to Chryslers get Champion.

dave1123

No worries, your excused. I'm just conscience of it because I own two 2000 4.0's

RealDealBJJ

Hey guys, so I started up the jeep yesterday evening and today and both times there have been no issues. The check engine light is still on because I haven't reset it yet.

Here is what I was planning to do:

Switch spark plugs from cylinder 1 to a different cylinder to double check the issue
If the issue doesn't follow, I will try the fuel injector swap

I left my torque wrench back in Cali, do you think its imperative that I rent one to do the spark plugs?
f the issue still doesn't follow, How do I test the coil rail? what is the process?

And then what are the steps to checking the compression?

also, do i need any specific tools for either of those tests?
Thanks for the help

Spencer_P

The problem I see is that the problem isn't consistent. The misfire has to be occurring when you swap plugs. I guess what I would do is swap the plug and clear the code then drive it and see if it changes to whatever cylinder you put it in.
I don't usually torque plugs, thread it in by hand (hand on the extension) then snug it up with a wrench and go about 1/8th a turn past tight.
To test compression, you can rent a compression tester gauge from a local parts store and the gauge will thread into your spark plug holes.

cruiser54

Just put a new plug in. Forget playing musical spark plugs and injectors at this point. No need for a torque wrench. Keep it simple.

dave1123

Cruiser's got it right. If you're careful, you can feel the seal washer collapse as you tighten it. When it gets harder, just a tiny scooch more. If the misfire is truly gone, the code may clear itself, but maybe not because it was a "hard" code for a while.

RealDealBJJ

Hey Guys,

thanks for the help. I'm replacing the spark plug now. This maybe a dumb question but the plugs that are in it are NGK-R's when I went to autozone, all they had were champion copper plus. will it be an issue if I have 1 plug not matching the others?

also, I got another code coming up P0455 EVAP major leak. I checked the tubes going along the bottom to the square box in the back near the gas tank and I couldnt find any indications of a leak...any idea what else it could be? would it be related to the misfiure?

RockyMtn96XJ

I would say when chasing a misfire problem, its best to keep things consistent. Spark plugs are cheap, so I'd say replace them all at once and not have different ones in there. These aren't race cars so having iridium spark plugs is only going to make them last longer, not perform better.. Rock auto has really good deals a lot of times if you can wait on shipping...

Maybe the Jeep just got so excited about leaving California that it is super happy and just freaking out with excitement.... Hahahah