Hi All,

My car is hesitating up to 4800 rpm - the boost can be seen fluttering at 3000-4800 rpm from 14.2 to 15.22 psi - then bang hit approx 4800rpm and it's steady at 15.8psi. I've checked the ignition when the boost is fluttering and it's fluttering around 9degrees (sometimes drops down to 3degrees) ,when I hit 4800 it's up to 11 degrees and advancing.
I've checked the idle and it seems a bit lumpy (720-750rpm - ignition 10.5-13.0 degrees) - is this normal?
It doesn't seems to have this problem when it's cold it doesn't feel like it's hesitating- but I don't want to hammer it when cold to get to full boost.
The car was running fine until one day when it wouldn't start (took 3 goes) and then the problem has become inherant - I've had the prblem now for a month and no dealers can find the cause - I've had the maf cleaned and replaced it - no change
Anybody had any similar problems?

It's got a full SS decat, normal air filter and dawes (still does the same without the dawes)

Regards

Lee

 

I get a similar hesitation (not jerky or anything, just feels like something is holding it back).
I figured that this is just the ECU going from closed loop to open loop, as monitoring the Air/Fuel ratio shows it running lean/stoich, then as soon as it goes mega-rich (indicating open loop), then the car takes off! So in other words, this hesitation is apparent only when *not* driving with full throttle. (Full throttle immediately triggers open loop). So it runs a bit too lean for the boost that it is getting with partial throttle, and this is only due to closed loop control of the air/fuel to attempt to run at economical & environmental fueling, and thus the power delivered is poor?

I also figure that this hesitation is less noticable on a stock WRX because the horsepower and boost characteristics are a little different. The turbo is slower to spool up due to the more restrictive exhaust, and so by the time the boost is at a good level, the ECU would have popped into open loop, so "smoothening" the power/torque response curve. We are peaking it out a bit with exhaust mods etc, so the jump from slow to go is more obvious.

Does this sound like a reasonable explanation of your situation (apart from the not able to start it bit....)?
R's
Tony

 

Hi Tony,

The car hesitates on full throttle - on part throttle it's not that noticable.

It's in at the dealers today to get looked at.

Regards

Lee

 

Have you checked your grounding connections. Sometimes if the grounds are not solid you can get hesitation. I had a similar problem on my US MY02 and it seemed to help.

 

Sorted at last!

SPARK PLUGS! - gaps were massive on them - and full of residue.

Don't know if it's because of the Dawes and increased boost/temps - bit surprised if it was the dawes as it's only been on for 2000 miles.

Also not sure if the NF was leaving residue (or optimax) - but it's running fine now.

Big Thanks to Danny at Mainland Widnes for sorting it : )

Anybody know what uprated plugs I can get for running 16.5psi?

Regards

Lee

 

Blitz Iridium plugs

www.performanceexhausts.net

Paul

 

The Subaru World Rally Team use Blitz Iridium!

(so do i)