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I have been hanging around here for a while and I want to make a few comments.
Troubleshooting problems is a science, it can be an art but it is not alchemy.
ODBII error codes are simple, direct and easily interpreted. THat is why we have them. They do one thing and one thing only, they give you data on faults for the fuel injection system (EFI).
Sometimes the ODBII codes will tell you exactly where to look for the problem. Example: Misfire on cylinder 5.
Some codes are more general and can be caused by a number of things. Example: I had a V8 throwing Lambda (O2)sensor codes and it was due to a leaking head gasket enriching the amount of oxygen in the exhaust mixture beyond the parameter stored in the ECU.
For starters I would suggest that if you want to solve problems on your vehicle that you go to a local parts house and spend $129 for a decent code reader. Mine tells me in simple language what the code means instead of only listing a fault code number.
Second, get a book on basic fuel injection systems and read it. It is not really complicated when you understand how the coolant temp sensor, MAF, fuel maps, O2 sensors and other bits interact.
The third suggestion is that problems in the trouble shooting process are usually due to a mistake in the basic set of assumptions that one enters into the process with. If trouble shooting does not yield the answer then look at what you are assuming to be ok and correct.
I had some buddies put a zip tie on the rear prop shaft of a truck I was doing an intake manifold job on. It took me less than 60 seconds to locate the noise and see that I was the butt of the joke.
Internet forums are helpful for problem solving with two caveats.
One: small simple problems are usually extrapolated to the most exotic cause becuase smart people want to show how much they know. Example: Intermittent miss in V8 was thought by another forum to be exotic valve sticking due to carbon build up due to faulty factoru design, turned out to be a bad plug wire.
Two: The spaggheti against the wall technique is rampant. Forum users will suggest everything remotely related to the system in order to guess what the problem really is and get to beat their chest.
In direct response to your problem.
First: look up the codes.
Second: Design tests to isolate the potential problem and test is it solves the issue.
Third: Fix the problem or examine your "givens" and start over.
Just buying parts and throwing them at the problem is expensive and has the potential to add additional variables to the trouble shooting that can obscure the thing that is causing the codes in the first place.
One of the most difficult for me was a leaking intake manifold on a V8. I replaced it and after went to start the vehicle. No start. Trouble shoot starter and no love. Replace starter, no love. Eventually after re-examining the givens, and much head scratching, I determined that in a completely unrelated problem, the power steering pump had locked up at or near the moment I shut off the truck to do the work and the motor could not turn fast enough in that state to start. Replaced power steering pump and life was good again.
Trouble shooting is a rewarding experience when approached properly. Don't just throw money at the problem.
Thank you for listening and carry on.
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