2003 GT- Rich Fuel...Why?

I had a clutch job gone wrong and ended up having to pull the engine and transmission as a unit. After re-installation, the car runs pretty well but has a slightly rough idle, a bit of coughing at low rpm starts, and a dash light for rich fuel. I've checked and double checked for anything unplugged or broken and cant see any problems. Any ideas on what could cause the rich fuel mix? I assume I must have made some error in the engine re-installation but I have triple checked on top and under the car and can't see any issues. Please help!

wmburns said:

Please post the full DTC codes. There are 1,000's and the each have a story to tell.

Did you remember to re-connect the grounding strap between the left hand motor mount and frame rail.

As for what "could" cause a rich condition:

• An exhaust leak.
• A disconnected or leaking fuel rail pressure sensor intake vacuum reference line.
• a dirty or damaged MAF
• A bad FRPS.
• A shorted signal return line from any fuel injector.

If asked for a handicap my vote is the motor grounding strap or the FRPS intake vacuum reference line. Anything else is really guessing. Trouble shoot based upon symptom following good trouble shooting basics.

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I believe it was code P0175 or P0172, The ground cable was on and tight; I just removed it and wire brushed the ends as well as the nut/screw that holds it in place and re-installed it. I replaced the Mass Air flow sensor after the re-installation of the engine (about 100 miles ago) and that hasn't accomplished much. I did have a hose come off of the DPFE sensor and I did have a minor improvement after reinstalling the hose but the light came back on after a few miles of driving. Thanks for the advice!

wmburns said:

Note that the list of things that could "cause" a rich condition is relatively short.

P0172 - System to Rich (Bank 1)

P0175 - System to Rich (Bank 2)

Air Measurement System

• MAF sensor (contaminated, damaged, corroded connector, etc.).

Fuel System

• Fuel pressure regulator (vacuum hose off, diaphragm leak, malfunctioning, etc.).
• Leaking fuel injectors.
• Fuel return line restricted.
• Fuel rail pressure sensor (incorrect reading).
• EVAP canister purge valve leak (when canister is full).

Base engine

• Engine oil contamination

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Thanks again for all of the Help! I will take another look at the fuel rail pressure sensor. I am pretty confident there are no issues with the injectors because the engine ran perfectly before we pulled it. I am pretty sure I replaced the EVAP purge valve as well about a year ago due to some emissions problems. I did have to remove the high pressure fuel line to the engine; is there any kind of special sequence during re-installation of the line to reduce air pockets or anything like that?