VZ LS1 misfire under load

[IDBHVE]

Hey guys,

I’ve just finished converting my VZ Calais from V6 to V8, and it now has a miss on cylinders 2&3 under acceleration.

Dash loom, engine loom, bcm, pcm, pim all replaced.

Plugs, leads and coils have been changed, injectors have been checked.

Happens around 1400RPM then smooths out around 4500 RPM

Any advice will be appreciated.

 

[Daniel Souza]

Hey guys,

I’ve just finished converting my VZ Calais from V6 to V8, and it now has a miss on cylinders 2&3 under acceleration.

Dash loom, engine loom, bcm, pcm, pim all replaced.

Plugs, leads and coils have been changed, injectors have been checked.

Happens around 1400RPM then smooths out around 4500 RPM

Any advice will be appreciated.

Which V8 engine and ecu are you using?

-On the VF service manual mention that vibrations on the drive train or suspension can cause some variation on the crankshaft speed and the ECU picks up as misfires. Just a thought.

-Check what is happening with the fuel trims when the issue is happening.

-Swap spark plugs and coils to see if the issue moves to other cylinder

 

[IDBHVE]

Running a VZ 5.7, bought a whole running, driving wreck for a donor car.

No codes come up, it’s only cylinder 2&3 missing under load

Plugs, leads, coils and injectors have all been changed, miss is still there in both cylinders

 

[Daniel Souza]

Hopefully it is not an compression issue. Has the engine had a compression test done ?

I guess it wouldn’t smoth out on higher rpms

 

[IDBHVE]

I did a comp test and all come back good.

I tested all injector wiring with a noid light and cylinders 2 and 3 the noid light goes dim and solid when it's under load, after doing some research, I've found that is cause by either a break in the ground circuit of those injectors, or the drivers for those injectors in the PCM are bad.

 

[Lex]

Sounds like the wiring harness for injectors needs replacing on that bank?

 

[IDBHVE]

It's 1 cylinder on either bank, so when I get home from work tonight, I'll be checking resistance on the ground circuit of all injectors with ignition on, then rechecking whilst the engine is loaded up and missing