Usmc4hire

My first post,

Vehicle: 1999 Jeep Cherokee XJ. 4.0 with 166k miles. Stock but for a lift and tires. Maintenance unknown, owned the jeep for a month and a half.

Problem: Misfire in cylinder #1 causing error code (P0301), rough idle, very rough drive, and gas smell out exhaust.

Additional info: Started yesterday. Jeep drove fine to work, fine at lunch, on the way home it started the misfire. Stopped at a mechanic on the way home who agreed with a misfire but wouldnt diagnose without $85. Drove it home, took my anger out on punching bag in garage, drove to another shop still misfiring. Next shop ran the code, detected misfire in #1, cleared the code, and the jeep ran fine on the way back home.
Started it this morning and the misfire is back. Parked it and stole my wife's car for the day.

Searching the internet has brought up all kinds of results and a ton from this site. I guess I'll start with pulling and inspecting the plug and wire. Any other ideas? As always cash is an issue here, dont have a lot of it.

storm101

I would start with the easy/cheap stuff, pop the hood and start looking at the ignition system, plugs, wires, rotor, and distributor cap.

Check the condition/connection of everything, it may be time for a tune-up.

The only other thing I can think of is an injector issue...I'm betting it's probably in the earlier statement though.

Usmc4hire

Thanks Storm,
I sure do hope your right. Cash is not in abundance right now. Again, thanks for the reply!!

mentalbreakdown00

As already stated pull #1 plug, see if it's worn out, check condition of plug wires etc.

Usmc4hire

K, checked plug and it looked great. Misfire still persists. Pulled #1 plug wire while running and there was no change to the engine so I can assume #1 is not getting spark.
Humor me and pretend your talking to a complete bone head.
What should be my next move and how should I go about it?
Thanks guys, I really appreciate the help.

mentalbreakdown00

Well lets start with making sure #1 has spark, if you buy a spark tester it will either plug in line or plug on the end of the wire, and clip to ground.

Bustedback

Check for carbon tracking inside the distributor cap. The best bet would be to do a complete tune up, plugs, dist cap, wires, and rotor. Do a compression test while you're at it. Use good ol' Champion or Autolite plugs, do not waste money on E3s or platinum plugs. Set the gap to specs and let us know how it works out for you.

tjwalker

Agree with above. You need to eliminate the plug, plug wire and distributor cap first.

Then the fuel injector and be sure it is getting a signal. A simple "noid light" can work great for that. (cheap and available at a parts store)

After that, run a compression test on all cylinders to be sure there isn't something internal going on. Compression spec. for the 4.0 is 120-150 psi, with no more than a 30 psi variation between cylinders.

Usmc4hire

Copy that, looks like I'll be making a trip to autozone. Stay tuned.

Thanks guys

papod

how about doing the compression test before buying parts?

Usmc4hire

Got new plugs, wires, and cap last night and did the simple install. Problem went away for all of 15 seconds. With finals all next week and my full time job I'm gonna have to go the lame route and have this thing professionally worked on. Just dropped her off at my trusted mechanic. Fingers still crossed for nothing major.

Thanks again for the help. I'll keep you posted as soon as I hear something (Monday afternoon).