Subject: 1g dsm help
Question:

i recently rebuilt my 1g 4g63 motor on my 1990 talon awd tsi. motor has
all new internals: full rotating assem., and full valvetrain job. all
built to stock except .05 oversized pistons. now the motor is in and
idles at 400 rpm, full throttle at 2400 rpm, extremely rich black smoke.
it would be great if you could help me with possible solutions, steps
to diagnose, and/or specs. i could use to double check motor
functions...
Answer: Raul,
I would recommend inspecting the mass air sensor and all intake hoses. There may be a vacuum leak anywhere from the intercooler to the throttle body elbow. Check the idle air controller (IAC) and adjust the ignition timing if necessary. Check the knock sensor and O2 sensor. Even a clogged catalytic converter can cause this problem. Blockages in any air intake or exhaust can cause this problem, so focus diagnoses on those areas first.
Good luck!