Monaro Misfire/rumble/power loss

[J8FF B]

Help anyone! Few weeks ago my 04 Monaro 5.7 VXR developed a misfire/power drop when warm. Very notable that its absolutely fine when engine is cold. Its possible even that since the mifire started it actually goes, and sounds, better than it ever did! Seems louder and has more grunt when cold and just about when temp gauge moves up the rumble and power drop occurs. Its very noticable through the clutch pedal and more apparent at 1250 to 1500 RPM! Its been on Tech 2 and Data Log and absolutely nothing comes as out of limits. Anybody got any ideas please.

[delmeekc]

Check your ht caps and leads, metal caps can be on but rubber caps not. Also if the engine gets too hot in traffic it always reduces power, I am sure someone technical will explain.

[essexhsv]

I think it will be your HT leads aswell. Theres been a few guys on here had the same problem where the HT leads looked ok but the engine ran fine after the leads were replaced.

[monkfish1]

Check the HT leads, then the plugs and coil packs in that order. These faults rarely show up on the diagnostics.

[Boosted LS1]

If it is a misfire would it show up on a rolling road if they do a plug trace with a diagnostics machine? This might get you a proper diagnosis. I'm assuming it's present all the time once the engine's warmed up. If you've not diagnosed a misfire then it could be vibration related caused by a mechanical issue. Sounds quite noticable if you can feel it through the clutch pedal. When did you first notice the problem and did it arrive all of a sudden or over time?

[DashRipRock]

My guess would be its the HT lead on the nearest spark plug to the driver.Its a real bitch to get to,disconnected from mine twice in 18 months.