07-06-2020, 08:14 PM
Welcome to the club. Funnily enough the engine check light has just popped up on my 2.0l 16v XSi. Just stuck it on PP .....bl**dy mixture regulation code again. That error doesn't unfortunately point to any particular element in the system involved in managing air-fuel ratio, making for a difficult diagnosis. In the past I've had lazy lambda, faulty MAP & TPS and yet on each occasion PP only gave me a mixture regulation code, not one that pointed to the sensor causing the trouble. Assuming you can't narrow much down via OBD data, any of the following could be looked at/for as potential culprits (in no particular order):
> Intake vacuum leak (In the UK, unless it was a tiny leak the car would possibly fail on emissions, so assume it would be the same where you are)
> Poor spark
> Fuel delivery - fuel pressure (pump & pressure regulator). Also poss check EVAP valve isn't sticking open.
> Lambda / O2 or associated wiring (but you've discounted that on the basis the car just passed its test)
> MAP sensor or wiring to it
> Throttle position sensor or wiring to it (could be a slight dead spot causing the hesitation as throttle opened. This usually happens near idle position. The TPS is easy to test using a multimeter).
> Mechanical cause
....I know it's a long list (but not even exhaustive). In PP you can at least look at some live data and get a sense of the information the ECU is receiving. If it's an intermittent sensor issue though, or it's only slightly out (but just enough to throw a light) then it can be hard to spot.
At the end of the day these aren't OBD2 compliant & you don't get a fraction of the diagnostic info you would from a modern car. That leaves you following intuition to a degree. If I were you I'd start with the TPS, then look at the MAP. After that, take your pick. Good luck!
> Intake vacuum leak (In the UK, unless it was a tiny leak the car would possibly fail on emissions, so assume it would be the same where you are)
> Poor spark
> Fuel delivery - fuel pressure (pump & pressure regulator). Also poss check EVAP valve isn't sticking open.
> Lambda / O2 or associated wiring (but you've discounted that on the basis the car just passed its test)
> MAP sensor or wiring to it
> Throttle position sensor or wiring to it (could be a slight dead spot causing the hesitation as throttle opened. This usually happens near idle position. The TPS is easy to test using a multimeter).
> Mechanical cause
....I know it's a long list (but not even exhaustive). In PP you can at least look at some live data and get a sense of the information the ECU is receiving. If it's an intermittent sensor issue though, or it's only slightly out (but just enough to throw a light) then it can be hard to spot.
At the end of the day these aren't OBD2 compliant & you don't get a fraction of the diagnostic info you would from a modern car. That leaves you following intuition to a degree. If I were you I'd start with the TPS, then look at the MAP. After that, take your pick. Good luck!