TJ Rough Idle when first started -
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post #1 of 5 Old 02-22-2008, 06:49 PM Thread Starter
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TJ Rough Idle when first started

I have a 2000 TJ with the 4.0 L six cylinder. When I first start it, it idles rough and I have to give it gas to smooth it out. Once I drive it for a minute, it idles fine. I recently had a check engine light. When Autozone hooked the code reader to it, it gave a message of a misfire in a couple of the cylinders. I replaced all the spark plugs, and the check engine light went off, but the rough idleing continued. Any help, please.

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post #2 of 5 Old 02-22-2008, 07:09 PM
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I'm not an expert on this, but it was suggested to me to clean the IAC and it worked very well. Very simple to do also.

Check out this thread and read post #2 by Jerry:

Give this a try first.
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post #3 of 5 Old 02-22-2008, 08:08 PM
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I have been having the same problem with the same year TJ. Hate to say it but I'm glad that I'm not the only one and will be trying out Jerry's solution.

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post #4 of 5 Old 02-22-2008, 08:31 PM
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I'm sure there are rough idling situations it won't cure, but it worked 100% for me. It seems at least once a week someone asks how to solve a rough idle. Jerry (or someone who read an earlier post of his) chimes in and it usually works.

Besides, it takes less than 20 minutes if you take your time (although the bottom 2 screws are a little tough to reach) so even if you don't totally fix your problem, it's a good thing to do.

If you want any more detail about how to do it, do an advanced search (if you can) for iac and jerry as the username. He has posted that response at least a hundred times and some of the threads have pictures in them, I just can't remember which ones.
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post #5 of 5 Old 02-22-2008, 10:56 PM
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if you have a missfire you need to check a coupple of things. If you can get someone with a vacume line and hook it to your intake a manifold. If your cylenders/pistons/valves are ok you should read about 18-19psi. If it varries more than that you have issues in the cylender. A missfire is caused by dirty/dead injectors, spark plugs, or like I said before a bad piston or something. Also Pull your spark plugs and MAKE SURE YOUR GETTING SPARK veary veary key. If you have access to a spark tester much much better. But pull each spark plug and have a buddy go in and give it a crank(remember to ground the plug). make sure you have good solid blue spark. If you find a non sparking plug(s) you've now narrowed it down a little. Now this tells you 3 things. A. Bad Wire(if you didnt replace the wires with plugs) B. Bad cap(pull off cap and look to see if you have a black line running between the points) C. Check for worn rotor(when you pull of the cap look at how much the rotor has worn down).

Hope this helps
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