Hmmm. Looking at the display, it shows 2590 misfires for #2 cylinder, but -0- for the #4 cylinder?
But back in reply #
17, the #2 plug looked OK, but the #4 has the signs of oiling on it?
I would be interested to see the difference in 3 spark plugs at this time:
* #2
* #4
* known good control spark plug (ie: cylinder that never misfires)
From here I'm going to guess that the #4 spark plug will still be showing signs
of oiling leading to misfiring. And that the #2 plug looks good? And hopefully
the known-good plug is clean and coloring to the good.
If this is what you find, then given that the engine seems to run well
until the
newly installed plug is fouled, then this shows that your engine can run smoothly.
But at the same time in order to fix this problem we have to locate/stop the
excess oil from wherever it is coming from? (Drawing oil from lifter valley due
to intake manifold gasket leak? Or damaged intake valve stem seal?)
****
NOTE: Assuming that the fouled #4 plug is causing the misfires, I don't have a
ready explanation for why it assigned the misfires to the #2 cylinder? But normally
the closer you get to the combustion chamber the more accurate the data, so I'd
tend to believe a spark plug pulled directly from the chamber vs the scan tool interpreting
the ECM data. Just from experience, this wouldn't be the first time that a piece
of test equipment has misdirected me. :0)
The distributor at the back of the engine falling behind the front of the crankshaft
is no doubt due to wear in one of the following places:
* Timing chain stretch
* knife-edge wear of the distributor shaft driven gear
* Excess wear between distributor housing bushing & distributor shaft.
Having said all that, I do not believe that a 5° variance of the cmp retard between
idle and highway speeds will affect how your engine runs. Since the actual spark
base timing is derived directly from the CPK sensor at the front of the crank, the
only real difference is a 2.5° (distributor, 5° crank) difference in the angle between
the rotor and the intended spark plug terminal in the cap.
And if we think that this is going to result in a misfire, then it should affect all 8
cylinders, instead of just 1. In other words, if we were to spend a lot of time/parts/effort
in eliminating this reading at highway speeds I don't think that it would fix this
fouling/misfire of the one suspect cylinder.
If I'm following your situation correctly, you will be away at the job for the next few days.
When you get a chance I'd like you to recheck the plugs mentioned above, and let us
know what you find.
Fingers crossed we can get the problem cylinder to quit fouling the plug, especially given
the really good compression test you posted. Too much is good under the hood to
not be able to get this running on all 8. (!)
Looking forward to your next status report.
