Unknown Misfire After Long Use

[tommyjt2006]

I am having a misfire problem after long periods of engine run time. It happens mostly on the highway after an hour or two. It will start to misfire heavily, so bad that the Service Engine Soon light comes on. The code always comes back Multiple Cylinder Misfire. The car has new 8.8 MSD wires, MSD Coils, & new ACDelco Irridium Plugs. It also has SLP Long Tubes, 3" True Dual Exhaust, No CATS, Bosch O2 Sensors, No rear Sensors, 2600 Stall, Vette Servo, custom PCM Tune, & Cold Air Intake. Any ideas of what is causing this? Thanks.

[2manycis]

Check your ignition module. chances are it's getting too hot and messin up.

[tommyjt2006]

I believe on the LS1 it's controlled directly by the PCM? It doesn't happen when hot, it happens after extremely long use (1-2 hours of straight driving or running)

[z28punk]

i would drive with a tuner and have the live data on the screen the whole time so when it starts misfiring u can see whats happening