MY01 hesitation
#1
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
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
#2
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
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
#5
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
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
#6
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