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Discussion Starter · #1 ·
I've been having an on going problem for the past two winters that I can't seem to solve and was hoping someone might have a solution.

Last winter my 2000 TJ developed a misfire in cyl's 1 and 3, this only occurs randomly during idle and only during the winter months. I replace the plugs last winter, which seemed to reduce the problem for a while.

It ran all summer without a problem but here I am again this winter with the same problem. I replaced the plugs again with OEM (the old plugs looked normal, no buring or fouling)but I'm still getting a MIL code. Most of the time when I get a MIL code it's cyl 1, but occasionally it gives me a multiple cyl misfire in cyl's 1 and 3 and yesterday it gave me cyl 4 for the first time.

I'm looking for suggestions as to what might be causing the misfire? My TJ has a spark rail that shares 1 coil for 2 cylinders, so I don't have the issues normally related to bad wires or a bad distributor, and as I said it only happens during the winter months and at idle. She has 120,000 miles on her and I was wondering if it might be valves or possibly a bad coil on the spark rail. This is driving me nuts and having limited funds right now I don't have the luxury of going to a shop and have them diagnose the problem. So if anyone has any suggestion as to what I can check I'd really appreciate it.

FYI, it's recently developed a slight engine knock during acceleration which I don't seem to have if I run 93 octane gas, don't know if it's related but I thought I'd mention it.

Thanks to all


· Registered
10,738 Posts
I'd look closely for a vacuum leak, like a cracked hose or?
A vacuum leak is most pronounced at idle - your symptom.
A vacuum leak leans the cylinder, making it harder for the cylinder to fire (raised required voltage.) New plugs fire slightly easier (lowers required voltage), so the vacuum leak isn't as noticable - for awhile. Hmmm, your symptom again.

Spray a burnable type carb cleaner around where leaks are suspected. Not all carb cleaners burn like gasoline, many won't burn at all. Gumout works. Be careful you don't start a fire. You can test the carb cleaners, spray a bit on the garage floor, if they'll light with a match, they'll burn in the engine like you need for diagnosis. If they won't burn on the floor, they'll act like water - not helpful at all.

Or, do the "propane trick" - do a search on past posts where I outlined how to do it.

Oh - why winter? Cool air is more dense.

· Registered
417 Posts
Kinda OT, but I am also having a problem with my '00 TJ. Since it has gotten cold, it will die out every once in a while at a light (when warmed up). It usually takes me by surprise because I don't even realize the engine died till I hit the gas. It starts right up, but I fear it won't do that someday.
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