98 Pontiac gtp running very rich


Asked by May 12, 2015 at 12:20 PM about the 1998 Pontiac Grand Prix 4 Dr GTP Supercharged Sedan

Question type: Maintenance & Repair

took car in for new cat, old one wore out leaking at collector and rattling in side, they
did some gas test and said have to fix rich condition before can install new cat. I new it
was running rich and had both o2 sensors replaced earlier. Also had replaced  injectors
earlier with bargain set bought on line. It has a hard to start problem except 1st thing in
morning.and intermittent up and down idle. air flow sensor replaced but still does it. It
also has a new maf sensor. My ECM is performance flashed and about 8 yrs old.
What am i missing here thks Andy

2 Answers


is the engine running cold? if so, replace coolant thermostat. that is another reason to cause a rich condition.

1 out of 1 people think this is helpful.

Turns out a 7.99 can of maf sensor cleaner did the trick. I removed the sensor and sprayed inside the maf housing, threw the screen, then the sensor. Let dry. Runs like a champ and has 280k miles.

1 out of 1 people think this is helpful.

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