XJ6 & XJ12 Series I, II & III 1968-1992

Intermittent engine miss

 
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Old 01-30-2009, 11:28 PM
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Default Intermittent engine miss

My 85 XJ-6, 4.2, has an intermittent miss at idle, in or out of gear, but mostlyout of gear,no load. Engine runs very smooth, except about every 10 to 15 seconds, then sometimes every 30 to 40 seconds, a very quick miss will occur. Nothing regular about the miss, very random. While driving no miss is detected. Might be there, just not bad enough to notice. Acceleration is fine, high speed driving is fine. Only at idle. Happens whether cold, or after warming up. The engine idles at 800 rpm out of gear, and drops to about 500 to 600 in gear. Everything seems normal, other than the random miss. Tonight I checked under the hood to see if there might be a light show among the spark plug wires, at the plugs, the coil, and in between,but nothing. New K&N air filter. Plugs haven't been changed, but would think it would be more regular if they were faulty. Its been there ever since I bought the car two years ago, and have gotten used to it, but would be nice if it wasn't there. Any ideas? Thanks in advance. Keith
 
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Old 02-01-2009, 04:42 PM
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Default RE: Intermittent engine miss

Update on intermittent engine miss. I posted this also on another site, and got several very good ideas. Several persons suggested the coil might be the problem. My 85 XJ-6 still has the original coil, with attached ballast resistor. It was suggested to replace the original coil with a V-12 coil, minus the ballast resistor. I've read about this for some time now, but never got around to doing it. Anyway, early this morning, I went out, just to take a quick look at the wiring on the coil and ballast resistor, disconnected the two white wires on the resistor, and noticed quite alot of corrosion. Didn't do a good cleaning, but did replace the wires, and removed them several times, to remove a little of the corrosion. This resulted in the engine starting instantly, instead of cranking for a few seconds before starting. Also, the miss is now gone. The rpms increased at idle out of gear from 700 to 1100 rpm, and in gear up to about 700 rpm. All is well, at least for now. I'll be ordering a new V-12 coil to replace the one I have now, and eliminating the ballast resistor. Hope this helps anyone with their series I, II, or III's. Keith
 
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Old 02-05-2009, 01:55 PM
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These cars manage our time better than we do. Just get one thing fixed, and it assigns you another task. Just like work. Got the interminent miss fixed, now my blower motors are starting to act up. Always something.
 
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Old 02-05-2009, 02:38 PM
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lol isn't that the truth.
 
 
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