Djgyro

Hi all,
I normally find the answer to everything in the previous posts but my MY99 Version 6 Sti has both me and my mech scratching our heads.

This started with the car "gasping" when I bounced the throttle so my mechanic (non-subaru specialist) suggested I change the TPS. I set that up myself and all apprered well. She ran fine for about 50 miles then the next startup it was running rough and the CEL came on and problems accelerating past 3k so I limped it home. I got 31 - TPS and 24 - Idle control valve as fault codes and the car hunted on idle.

I checked for vac leaks and cleaned the idle control valve, reset the ECU with no fault codes but still hunting so gave to the mech to have a look. He also checked for leaks, tweaked the TPS and it still hunted so we agreed to replace the MAF sensor according to posts on Scoobynet. I should point out that normally I only use Subaru parts but because we weren't 100& this was the problem, I got a new non-descript sensor figuring if it was this, I'd get a genuine one and if not, I'd refit the old one. The new one is still fitted. Now shes stopped hunting on idle but its lumpy and running rich.

I've just done a reset and test-drive this morning and no fault codes but interestingly the CEL started flashing regularly after only 30 seconds from cold. I was under the impression the car needed to warm up first. No fault codes in the ECU at the moment but the idle is still rough, running rich and doesn't drive smoothly (but no hunting RPM and doesn't stall on idle).
Out of interest, I changed the MAF sensor for the old one and it was 10x worse - very lumpy and hunting so the new one, albeit a cheapie, seems to be an improvement. Could it be that it's because its a non-genuine MAF?

I'm also starting to suspect a problem the engine temperature sensor as it does idle better when warm than cold.

Anyone got any ideas what I can do to diagnose the problem further?

Thoughts gratefully appreciated

1509joe

iTrader: (2)

MAF's are notorious on v5/6 cars try unplugging it and see is there any improvement. Genuine one would be beneficial. O2 sensor only reports a fault if the heater circuit is bad iirc.

Djgyro

Thanks for the reply, I've just been out and tried unplugging the MAF and it stalls immediately. Interesting about the O2 sensor. That one is an expensive one if it turns out not to be the problem...

1509joe

iTrader: (2)

Strange one that usually they default to get me home values as such and run ok ish with the MAF unplugged.

Djgyro

Would that suggest that another sensor is faulty?
If the ECU relied on data from another sensor(s) if the MAF is unplugged, and their data was corrupt, maybe that would cause it to stall?

1509joe

iTrader: (2)

Quite possible. Could also be the reason your check engine light was flashing.