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2003 Chevrolet TrailBlazer EXT - What are we missing

Car ran well in warm Texas weather. \When cold came, car would shudder so bad seemed would come off its blocks. Turn off, restart, run a bit, runs OK, but check-engine light on and throws ‘lean’ code (making fuel too rich, which burned up the catalytic converter). EVERY possible part, one-by-one which could be the problem, has been replaced OVER A FOUR MONTH PERIOD. Down to the computer now, but it would not reprogram; still ‘lean’ code and hesitates on acceleration into traffic (dangerous). Warm spell comes along and starts and runs well, but ‘lean’ code still present and dumping rich mixture will eventually take out the cat again. Mechanic has stopped charging me at about $1,500 (could have dropped in another engine or that price) and is as frustrated as I am. He is on a crusade and determined to solve the problem. I believe THE PROBLEM IS GENERAL MOTORS DESIGN! Help! Retired and I cannot afford another car!

A ‘lean code’ in my book is an indication that the fuel mixture has too much air in the fuel/air ratio, not excess fuel, which is too rich. You need to look for an air leak source somewhere between the Air Flow sensor in the intake and the O2 sensor in the exhaust system. Like the intake manifold or exhaust manifold areas. Vacuum lines should be checked also.

You might check the fuel pressure regulator, easy check pull the hose connected, if it smells like gas it is toast.

I believe the problem is poor or incomplete diagnostics by the mechanic working on the car. The Trailblazer has a pretty reliable powertrain and I see fewer of those with driveability problems than other GM models.

How about providing a list of the parts replaced and the fault codes reported? By the way, replacing parts because of a fault code without testing is a poor repair method.


Several reasons for a “Lean Code”, each one will give different codes.

What code are you getting ? P0000

If it was a design problem all the trailblazers would do that. When I hear that a mechanic has replaced everything that can make it do that including the computer, I just want to hold my head in my hands.
Some “mechanics” just replace the commonest parts that can produce a particular problem. The can get by like this for enough customers to stay in business for the most part but this approach leaves them unable to do a proper diagnosis. They either don’t have the right knowledge, equipment, or aptitude.
I applaud him for stopping charging you at some point, so he is not a bad guy, but I don’t think he is a great mechanic.

I don’t have an answer for you, but if you can provide the codes in the form of Pxxxx, maybe some one can.

Agree with @asemaster The problem is with your mechanic.

As for blaming GM… the truck is 16 years old. There will be problems with a 16 year old truck!


“What are we missing” . . . ?

A competent mechanic

The shotgun approach is the hallmark of a mechanic with limited diagnostic ability

Does the mechanic who replaced “everything” know how to interpret pids on the scanner screen in a useful fashion?

Or does he not even know what he’s looking at?

I suspect the latter


In the final analysis, a tiny bit of debris was clogging the needle-hole of the oil pressure sensor, which cam serves to set the timing, and when the cam was turned (tight at first) the debris apparently was ‘squished’ through the hole and washed down stream. NO PROBLEM SINCE THEN! Something so simple was causing the never-ending and virtually undetectable problem. Much was replaced in the process, but I have a ‘new’ car now and do not regret the wait.

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