Usually in a rich condition a vacuum leak is not what your looking for, this would give you a lean condition, and lean codes, not rich. P1172 and P1175 are lean codes. In this case where you have a rich code, The processor could be compensating for a vacuum leak by adaptive strategies
Is the engine idling high? Around 1200 rpm or low?
Has the engine been loosing power ? gutless?
Last tune up and plug change ? and mileage on wires and plugs.
Does it seem to be missing at all?
Have the HO2S, O2 sensors ever been replaced? And how long ago?
At this point some of the possibilities are as follows:
1 Oxygen sensors, Highly likely the problem. Test them first with ohm meter, and make sure the heater circuit is working.
2 Cats plugging up, check back pressure = gutless question
3 Faulty iacv stuck in a default position. This is why I’m asking the high or low idle question.
4 Miss fires plugs not always lighting the a/f mixture.
5 Coking: this is where the intake is very oily inside, usually due to the crankcase ventilation system……. Pronounced: coke…. ing
6 Ring and or valve guide issues.
7 Although rare, injector or injectors stuck partially open.
8 Faulty coil pack, intermittent problem only.
9 Block or ground issues
10 Faulty processor
11 Fuel soaked Evaporative canister.
12 Fuel pressure too high.
13 Iat sensor out of range ( Intake air temperature )
14 Restrictions in intake
