Losing boost when warm.

[stinger_007]

Ok, heres the deal.

I've just fitted a gates timing belt kit and nevo pulley. (note: this problem was around before, just not as noticeable).

When the car is cold, it will boost to 11 psi. (7 before nevo).

Once its been running for 10 mins (operating temp reached), it drops to 5 psi (2-3 before pulley)

It also blows black (fuel) smoke on hard acceleration.

It could require a tune (factory ecu), but when cold it runs clean as.

I was going through my wiring harness last night, and found what looks to be a o2 sensor connector.
This was not attached to anything. but ran into the main harness.

The engine did have aftermarket managment before (ems 4424), it could be left over.

QUESTION :

Does the factory aw11 (4agze) run a o2 sensor in the exhaust?

Could this be why it is overfueling when warm?

Is this the reason for my missing boost?

Cheers,

Phil

[ke70dave]

don't quote me here.

but i was under the impressing that factory ecu's only use the 02 sensor when cruising along (like on the highway) to make fine adjustments to the mixture. this is becuase they use a narrowband o2 sensor which takes about 10secs (maybe longer) to react to fuel mixture changes. which makes it unsuitable for use when revs/load are changing to fast (ie driving around town etc)

so therefore not needed on normal driving, it just improves fuel economy at cruising speed

i can't really help on the rest I'm afraid

[dustyae86]

<div class='quotetop'>QUOTE (ke70dave @ Feb 11 2008, 10:33 AM) </div>hmm possibly the ambient temp changes and it sucks in hot air and can't compress it so much?? my car does run rich too though, not sure if it's common or maybe my tune

[Hen is a total nutcase]

O2 sensor does only adjust fuel when running in closed loop mode (cruising, light load, etc) and apparently it only adjusts fuel +/- 5%. So the oxy sensor is not your problem.

I'll suggest a big boost leak. Maybe a split pipe or leaking clamp that only gets bad when warm. Given you have an AFM, a boost leak would explain both the lower boost and the rich running.

Hen

[stinger_007]

i'll check my piping again.

It odd becuase once the motor is turned off, cooled (20mins) it has full boost again, then 10 mins later its droped off.

[dustyae86]

<div class='quotetop'>QUOTE (stinger_007 @ Feb 11 2008, 12:39 PM) </div>good one ben, yes i would definately suggest that!!

[slide86]

have you done the ABV mod thing?

perhaps the bypass valve is staying open when the engine warms up (for some reason)

[stinger_007]

Yeh, abv mod done.

At idle no leaks apparent, its tough to have boost and look in the engine bay!

Check again tonight.