90 XJ idles and runs rough. Feels like spark

My father has a 90 XJ that is running real rough at idle. He says sometimes when he steps on the gas softly it dies. Always starts right up but then idles rough again. He has been a mechanic for 60 years but doesn't know computerized moters too well. He is sure it feels more like a spark issue then fuel. Any help?

Hey Moab, my Dad just had to do the electronic control module (equivalent to the coil) on his '90 a couple of weeks ago, are there any other symptoms that it's giving? He also thinks there might be a chance it could be a crank trigger sensor but that ECM seems to give him the most problem (I think this is #3 or#4 now.) He also said to check the vaccum lines over the valve cover to make sure the oriface isn't plugged up, ha's had that cause the same problem too. He may even want to check to make sure the throttle body isn't oiled up, both can be caused by excessive blow-by I guess.

DrMoab said:

My father has a 90 XJ that is running real rough at idle. He says sometimes when he steps on the gas softly it dies. Always starts right up but then idles rough again. He has been a mechanic for 60 years but doesn't know computerized moters too well. He is sure it feels more like a spark issue then fuel. Any help?

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Renix fuel injector connectors aren't great (trap moisture, corrode, etc.) and it will feel just like a spark miss. Check 'em carefully, if the boots are cracked or damaged, very likely to be a problem. Use a good light and eyesight to qualify the connectors.