Heinz57 Posted October 3, 2016 Share Posted October 3, 2016 My son has a 2001 Cherokee Sport 4.0 liter. We are getting intermittent misfire codes. Initial misfire code was on cylinder #1. Engine starts and idles rough. When accelerating down the road, significant missing at 40mph and can't accelerate beyond that (engine light is also blinking). Sometimes it works itself out of it after turning it off/on. Other times, no rough idle and all runs well. First think I did was replace the throttle position sensor. No luck. I then replaced spark plugs and the coil rack. First code I got after that was misfire on cylinder #5. So, I put the old coil rack back on to see if the misfire would go back to cylinder #1. It ran fine for a week and then the cylinder #5 misfire and rough running at 40mph came up again with the rough running engine. It worked itself out again and has been driving fine for a week now. I saw the recent related posts, but our problem seems a bit different. Really puzzled. Any thoughts? Quote Link to comment Share on other sites More sharing options...
Administrators Moses Ludel Posted October 4, 2016 Administrators Share Posted October 4, 2016 Heinz57...Understand your frustration. Frankly, this sounds like a PCM or PCM connector problem. I would disconnect the battery negative cable and try carefully disconnecting and reconnecting the plugs at the PCM. See what that does. Clear the stored codes and start again. If random codes occur, I'd be suspect of the PCM. The fact that the engine is capable of running well hints that none of the individual parts (injectors, coils, sensors, etc.) has failed. What's left? The PCM. See if there is an inexpensive dealership test for the PCM. If not, consider contacting or sending the PCM to a shop like Module Master: https://modulemaster.com/. This is rapidly becoming a rebuild industry of its own, there are other shops as well. Other causes of random issues include system voltage (charging current, resistance at the ignition switch, etc.). Note your gauge readings if/when the troubles begin, voltage reading in particular. Moses Quote Link to comment Share on other sites More sharing options...
Heinz57 Posted October 4, 2016 Author Share Posted October 4, 2016 Moses - Thanks for the quick reply and ideas. I'll investigate them and let you know. Quote Link to comment Share on other sites More sharing options...
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