02 Tahoe Heavy Misfire P0300

[Madgrty]

I wonder if P/O got a donor motor out of an express van... I'll have to look it up again but I'm 99% positive that the were all drive by wire (electronic) not cable driven

 

[D M 3]

Ill look at it in the morning. Gonna check some things on it.

 

[Madgrty]

Alright I was wrong, from 1999-2002? Maybe 03 but I believe if you either hadn't got traction control or cruise control it came with a cable TB. If you had those options then it came with the electronic TB.

 

[Tonyrodz]

My 03 is dbw.

 

[retiredsparky]

I am surprised that temp sensors were not changed- Intake air and coolant temp sensors can affect the fuel mixture and are not real expensive. If the PCM thinks the engine is real cold, the mixture will be extra rich.

Have you checked the spark plugs to see if any of them are blackened to see which cylinders are running rich?

You could have injectors that are not shutting off properly. Or injectors whose spray patterns are not optimal any more. If the fuel doesn't atomize correctly, some will not ignite properly. Remove them and have checked and cleaned at an injection shop.

Has the compression been checked? Low compression could cause incomplete combustion.

You didn't say that the plugs and wires or air cleaner had been changed. These are pretty common maintenance items.

I suppose a last resort would be to find a used or new PCM or have the PCM flashed at an independent shop or a dealer.
Larry

 

[D M 3]

Ordered a rebuilt ECU. I think this is the issue after speaking with previous owner. Hopefully it works will let u guys know. Thanks

 

[Tonyrodz]

Hopefully that's the issue and you'll be done with it. What made you come to that conclusion?