Misfire Cylinders 1 3 6 - Weird Situation

[tscribne]

From my mechanic, any suggestions?

Basic Problem: Rough Idiling, Misfire on cylinders 1,3 6 with codes to say same.

Hello Tom, it's really not playing nice. We have checked damn near every component. Compression, Coils, Plugs, even did a leak down on the injectors, Fuel Pressure, Exhaust Back Pressure. The Misfires are on 1,3 and 6. We swapped coils and plugs from those holes to the sister holes and misfire stayed in the original location. Compression is within specs 130-140psi. It had 9 codes related to the Exhaust pressure sensors yet no faults can be proven there. He did locate a pinched with near those coils so he repaired that but no change. He was a bit concerned that that may have damaged the DME but has not found anything that would say this is the case just yet. The valve adjustment was brought up but typically they are loose when they need adjusted and this doesn't cause misfires (every time) so we have not gone there yet.
That said. No answers just yet.
So much fun is being had.

Any suggestions?

Thanks,
Tom

[dworthy]

Welcome to the Forum!

Wait, 130-140 psi on all cylinders? This is a high compression motor and you should be seeing 145 - 160 psi. Valve adjustment can play a part if they are way out, I wonder if the test was conducted properly.

Next would be to check timing, for that too can lower the compression some.

Has the VANOS bolts been looked at? How about the exhaust hub tabs? Timing chain guides?

[dworthy]

Welcome to the Forum!

Wait, 130-140 psi on all cylinders? This is a high compression motor and you should be seeing 145 - 160 psi. Valve adjustment can play a part if they are way out, I wonder if the test was conducted properly.

Next would be to check timing, for that too can lower the compression some.

Has the VANOS bolts been looked at? How about the exhaust hub tabs? Timing chain guides?