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2004 Chevy Trailblazer 4.2 Lt 6 cyl.
Service engine soon light is on DTC P0172 Fuel Trim System Rich.
Repairs = Serviced transmission, changed fuel filter, air filter and spark plugs.

Question = Symptoms, Engine runs very rough with very little power to go up small hills on
highway. Trans was serviced because it was time and while it was in shop I just had it done. After
the new plugs were installed it runs not much better. I am stationed in Germany with the military
and it is hard to find qualified mechanics to work on American vehicles. I found your web site
through yahoo and I am glad you have such a site!!!!!!

Many things can cause p0172-
rich condition. There is a computer re-programming available to
correct this code, but not usually a running problem with the engine.

Things that can cause this are excessive high fuel pressure, a stuck open injector (s) caused by
contaminated fuel, poor fuel economy, vacuum leaks, a leaking fuel pressure regulator, or just a
oxygen sensor.

If running so bad, there should also be a history in the computer for which cylinders are misfiring.
A live data stream through a scanner would reveal that. This could give indication as to which
cylinder (s) have a problem.

Would suggest having fuel pressure checked, should be about 50psi.
Pull the vacuum hose off the fuel pressure regulator to look for signs of fuel in the vacuum hose.
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2004 Trailblazer Code P0172