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Engine Missing vz commodore 04 model, approx 250 ks

Morto

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Hi,

Have a vz commodore that has a liquid gas conversion. Has been running rough for a little while, took it to the mechanic and he put new plugs, made no difference, so I took it back and he put a new set of coils in. Still ran rough and almost immediately it threw up the code po202.

I put a new set of injectors in and it continued to miss and throw the same code, I guess I should have thought a bit about the gas injection as even if the injector was failing, the gas injection should have still worked ok. I pulled off the feeds to the coil and it seems to be missing on No 1 cyl (as you face the engine the 1st cylinder on the left hand side), i think p0202 should have been the first cylinder on the right side as you face the engine.

I have swapped the coil from cyl 1 to cyl 3 and it continued to miss on cyl 1. I then pulled the plug on cyl 1 and replaced it with a new one and guess what? It still misses, continues to throw po202 code.

Any advice would be appreciated.
 

99notout

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Put a noid light on the injector plug and see if it is flashing as you crank the engine. If it is flashing then suspect the injector, easy fix, If it isn't flashing, then it still could be the injector, as the ECU will temporarily disable the injector circuit for a bad injector to stop raw fuel going out the exhaust. So, if not flashing, then remove the negative battery lead for a minute, and try again. If you then have the noid illuminating, you can say the injector is probably faulty, or the plug is loose etc. If you still can't get the noid light to flash, it gets more complicated!

P.S just 'cause you had new injectors fitted, don't think for a minute one could be faulty! I would personally look at the injector connection, and where they tapped into the injector harness for the LPG impulse feed for loose connections, or corroded joints.

Good luck.
 

180Sv6

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Hey mate, just went through the exact same thing on my 04 sv6 same code on cylinder 2 . After testing the spark plug, coil pack, and all wiring from plug to to plug even pulled the coil pack out and watched the spark plug fire it led me to believe it was the injector so I swapped the injectors. still misfiring on the same cylinder, after running leads out from the injector plug and injecter loom so I could test it while the car was running . Turns out I was intermittently getting the injector firing signal. After testing all the wiring back to the ecu turns out the ecu was caput and only sometimes sending the signal to the injector, swapped the ecu and she's running fine again. Test everything and see how you go but apparently it's a common fault for the ecu's to **** themselves .
 

Morto

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Checked the wiring harness as suggested, could not find any problems with the gas line tap-in. Checked the injector line with a noid light and the fault was there, connections were fine. I then bridged cyl 2 to cyl 1 injector wires in the harness (as suggested on another thread), everything works well. I know its not a perfect fix, but seems to be better than spending another thousand on an old car.

Thank you to everyone who replied for their assistance.
 
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