Hi
I am new to this site. I have a 89 cherokee , with 185 thous. miles. It runs well and I have resently replaced the crank sensor for a no start problem I had. I have now noted a flat out miss under a mild load or cruise. It is as if it is just one cylinder. But its so strong it makes the car jump like you hit somthing. Since it is not consistant 3 or 4 miss fires at once , could it be the coil or coil wire. I would like to get ahead of this problem before I end up going
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89 4.0 auto air 4x4

When warm does it miss at idle? And it does not miss at full pedal? If so it could possibly be a leaky intake valve. I'd be doing a leak down test.
A jerky miss at mild throttle can be caused by fire leaking into the intake manifold.
Does it backfire up front or in the back when it misses?
Big Jim

when cold start and warmed up there is no miss , well except when warm there is a very faint single miss every now and then that does not even make the tack needle move. I figure this is expected with the miles on the car. It seems to only occur when at mid throttle and at a steady speed. I have felt a miss caused by plug wires breaking down and its different.. not several misses just a single hit (miss) does this help

Ok that sounds like one of the electronic pieces is breaking down under heat. Could be coil, dist pickup or sparkbox. Might be tps? I betcha as the weather warms up the part will fail completely.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />

Snowing today and the wet air seems to have made it a little worse. After dark opened the hood and did not see a nice light show (like spark plug wires arcing), But did notice a sound like an plug arcing when the miss occured. useing a half inch hose I placed one end to my ear and the other around the wires. I noticed a louder zap at the coil wire to the cap and at the coil it self. Both coil and cap male connector for the coil wire had corrosion. cleaned with a small brass brush. will have to test tomorrow. Would this little corrosion cause enough resistance to make a coil work harder

put a little dielectric grease on it and the corrosion should stay away.