hohl

I set the P0300 random misfire code tonight, but it seems that the misfire is not so random. #3 is misfiring three times more than #2 then 1,5,7 are all misfiring but less than 1% of #3.

My thoughts are that #3 is causing the misfire on #2. Is this wrong since they fire so far apart in the firing order? Is the misfire on 3 responsible for all the passenger side misfiring too?

The misfire on 3 goes away with RPM; less than 2500 RPM with varying TPS and LOAD. At WOT the misfires are as high as 64 but go to 0 as soon as I surpass 2500 RPM. Peaks between 2300 and 2500, right in my freeway RPM range.

This is a rebuilt LS1 that I swapped into a Tahoe and am running it with the 5.3 PCM and am using edit. Is this a classic example of CKS relearning required? The plugs and wires look good. I haven't tried moving the coil pack since the misfire goes away after 2500 RPM.

Black LS1 T/A

I know you said they look good, but it sounds a lot like fouled plugs.

hohl

OK. Even though these plugs are brand new, less than 500 miles, I have tried several different tunes so I replaced them and saw no difference. While I was changing the plugs I checked the resistance of all my wires. They all came in between 400 and 420 ohms, well within the factory 700 ohm limit.

I still see the same misfire. Number three...a lot with number 2 and number 4 misfiring when number 3 misfires get above 40.

I thought it might be ignition/coil pack related so I pulled it off and replaced it with a known good one.

What else should I look at? If it needed to have the CKS relearn wouldn't it misfire on more than one cylinder?