Misfire problems

[sambo]

After a couple of days troubleshooting this I'm throwing it over to the brains trust.

Things were just going too well in the lead up to the IM240 test and my L98 (think LS2 if Stateside) has decided to throw multiple fault codes on cylinders 2 & 4. The engine goes into limp mode and runs extremely rich as a consequence. Engineering process has been halted and the clock is ticking.

The engine was making plenty of power until about Tuesday this week when I noticed a drop in power and rough idle part way through a test drive. This is a new crate motor with maybe an hour of running time and no abuse or obvious signs of damage such as smoke, noise, etc.

Codes picked up by the scanner: 202 & 204 (cyls 2 & 4 injector circuit malfunction/open), 300 (multiple cylinder misfire), 302 & 304 (cyls 2 & 4 misfire), 1381 (misfire detected). Plus others that are unrelated such as no comms from BCM.

The following tests have been conducted, the ECU reset and each time the codes come back after a short drive.

• Swap injector 4 with injector 8, fault stays at injector 4
• Swap coilpacks 2 & 4 with units from another car
• Swap leads, plugs
• Noid light shows injector plug working, flashes faster on accel
• Compression test cyls 2 & 4, both around 175 with hand held tester (minor leakage possible)
• Remove, apply compressed air and reseat both ECU plugs to engine loom
• Continuity test of coil pack wiring harness, OK
• Spark plug lead tester shows good arc

If you have any questions or suggestions please post them. I expect a few Ford vs Chev jokes but may not take the bait as I'm pretty over this little 'problem' right now.

Thanks

Paul