Only Rev till 2500 RPM - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 12-05-2000, 04:06 PM Thread Starter
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Only Rev till 2500 RPM

I have an '87 YJ with a 258 I6, unfortunatlly the stock tranny, have done the TR upgrade, put in MSD bypassing the computer and still the engine power dies off once i get till about 2500 RPMs in any gear. I thought the TR upgrade and MSD were supposed to solve this problem? I will be installing a Weber in a few months. Will this solve the problem? Right now I have a rebuilt Carter on the engine. I noticed it in city and highway driving. If anyone has any ideas, please let me know. Thanks.


1987 YJ 258 I6, 5 Speed, TFI Upgrade, MSD 6A
1999 Cherokee Sport, Stock
donnyg is offline  
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post #2 of (permalink) Old 12-06-2000, 08:48 AM
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Re: Only Rev till 2500 RPM

Have you checked the timing recently? If timing is set correctly, check and see if your vacuum advance on the distributor is working when you rev the engine. You should be able to see it move. If it doesn't, it may be stuck or the diaphram is toast. FIRST, check that there is actually vacuum pressure in the line to the distributor. You may have a vacuum leak someplace causing this problem. Good luck

Tommy B. in AZ -
post #3 of (permalink) Old 12-06-2000, 08:56 AM
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Re: Only Rev till 2500 RPM

What can you see move on the distributor to make sure the vacuum advance is working??

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post #4 of (permalink) Old 12-06-2000, 09:14 AM
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Re: Only Rev till 2500 RPM

There is a spot right behind where the vacuum line connects on the left side of the dist. (Right where the cap sits on the metal part of the dist). If you can't see it because you installed the Ford cap, use this simple test... Pull the vacuum line off the distributor while the engine is running. The engine should run a little slower/rougher. If it doesn't, check the line to make sure there is vacuum. If there is no vacuum, then you have a vacuum leak or disconnected/incorrectly routed vacuum line. If there is vacuum in the line and the engine speed doesn't change when you pull the line off and put it on, the vacuum advance in the dist. is shot and needs to be replaced. The same thing happened when I bought my YJ. The vacuum lines were all hosed. One more thing to check would be the choke, make sure that is fully opened when the engine is warmed up. And check that the "trap door" on the air cleaner is opening when you rev the engine.

Tommy B. in AZ -
post #5 of (permalink) Old 12-06-2000, 09:16 AM
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Re: Only Rev till 2500 RPM

Thanks Tommy!

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