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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
faulty 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.
2004 Trailblazer Code P0172