Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP
What engine do you have?
I have a feeling I know what is wrong already.
With all the swapping you have done so far, does it have injector pulse tested with a noid light on those two cylinders?
I was thinking you might have had a AFM LS 6.0 litre.
With your V6, what do you mean by "shimmed crank"?
Do you mean the sensor?
DOES THE INJECTOR PLUG FLASH WITH A NOID LIGHT as requested above?
1 and 4 are 360 apart, could be something wrong at the sensor face or the reluctor wheel on the crank.
You did not state what engine you had in the first place.
I know your engine is a V6 after you said which car you have.
I have seen dropping multiple cylinders in LS engines where the fault IS mechanical.
I have been with GM Holden all my working life.
Cylinders 1 and 4 in your firing order are 360 degrees apart.
So if you can't answer my question to you about why you "shimmed the crank", I think you mean the sensor, don't know.
Did you look at the reluctor wheel while the sensor was out, maybe it has a bent tooth?