Thread: Lumpy idle v6
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Old 29th February 2020, 04:53   #9
kaiser
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Quote:
Originally Posted by bl52krz View Post
Could be the plug breaking down under compression. No slight cracks in the coil when you had the plug out to check for spark?
No, we have swapped the spark plugs between cylinders 3 and 5 (middle and right) and the misfire stays on cylinder five.

So to recapitulate:
Compression is good. Spark plug is good. Spark fires at all times (checked by pulling plug lead at different revs). Cylinder fires at higher revs (also checked by pulling plug lead at different revs). The injector has been swapped (which didn't seem to make a big difference).

So by elimination, the idea of water getting into the cylinder fits the bill, except there is no evidence for that. Which leaves the possibility that the injection control can be faulty.

Is it possible for the control to one cylinder to be out of spec? Either too long or too short delivery, or wrong timing???? But only at idle.

That is about the only logical option I can see left.

The only other option is that the swapped injector has a fault as the original must then also have had. The only way to make sure is to also swap the injectors like the spark plugs and see if the fault follows the injector or not. That is possible, but I guess unlikely.
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