LS1 swapped (cams/headwork/professional dyno tune on stock PCM) Racecar ran amazing for 3 years. Then led a series of issues at the next 3 or 4 events;

- Misfire feels like running on 7 cylinders so swapped wires after finding some header contacted wire and cured for a day

- Misfire returns next event feels like running on 7 cylinders again so swapped wires again problem continues

- New plugs/wires/sensors all over the motor, problem seemingly getting worse with now problems as soon as you go to tip the throttle in off idle

- Car bogs down with any throttle application

- Shop screws around with it for 6 months and replaces all the sensors I already replaced.

- Now time for me to get back to actually diagnosing whats wrong. Have good fuel pressure so went to checking spark.

- No codes being thrown or misfires being detected by the worthless GM PCM

Can anyone explain this? The plug wires induce the timing light/rpm detector on ALL drivers side plug wires but do this on the passenger side plug wires:

https://www.dropbox.com/s/hxwxanzwn4...38.05.mp4?dl=0

I swapped one of the "bad" coil packs to the other side and the problem remains. Do I start tearing apart the wiring harness all the way back to the fuse block for this side of the ignition bank or is there a better method for next steps? Do I run a compression test? Is there something I can monitor with my scanner while running that would help narrow this down? Guess I could check O2's for that bank and see if they are running really really rich or would it be fuel trims that would go really negative on that bank to compensate for lack of spark if that was the issue?

I recently found that my emergency shutoff seemed to be failing and intermittently screwing with my power feed to the fuse block so jumpered that for the time being while I sort this out (although that may have caused some of this issue to being with).

Thanks in advance!

 

Check for power and ground. You then can go from the PCM to the Coil packs and check resistance of all circuits. Need under 2 ohms.

 

Bought and used a spark detector and it's showing spark on the cylinders in question so dead end there. Bogs down under throttle with all new sensors and new intake manifold. All headers seem similar temps any suggestions for next options to diag? Compression testing each cylinder a good idea?

Should I buy Hptuners and turn back on misfire detection to see if one of the cylinders in particular is misfiring?

Car was tuned by Speed Inc and ran great for 3 years before this issue.

 

What's the wideband say? Fuel trims okay?

Does the car have cats? Or any other exhaust restrictions?

 

Zero cats, basically a center dump exhaust dual 3" magnaflow muffler.

My foxwell reads all open loop and fuel trims show constant -1 both banks ST/LT I believe.

Not sure why it won't go into closed loop. New O2 sensors also due to a pending P0135 code nothing changed.

Should I buy a software so I can turn back on misfire detection to try and narrow this down?

 

Swap coils for known good coils, don't move them to the other bank. If you have access to a scope, you can scope coils and injectors and will find problems with either pretty quick.
Are you using factory Crank sensor or flying magnet? Again, a scope can point out shifted reluctor on the crank (not the sensor). I always go with the KISS principle...it will probably be something simple if it ran great for all that time, but sensors have to be getting good info to process.

 

I would check grounds as stated. Try changing out coils as stated. I’d check fuel pressure at the rail while trying to give it gas with a load (drive).

 

Bought HPTuners and started moving things around after I finally figured out how to turn on misfire detection.. PROGRESS! After swapping fuel injectors from bank to bank, the dead lean O2 sensor reading swapped banks and the O2 sensor went from flatlined 18mV to switching normally!

Ordered a new 42# injector and will update once I have finalized repairs.