Evo Ace

Please help I've a 1999 sti. If I floor the throttle at 3000rpm after running on a very light throttle (say waiting to overtake in 4th at about 50mph) the car splutters almost slowing down for a few seconds before accelerating well once over about 4000rpm. It actually accelerates better if you just use part throttle, also it's much worse when cold. Any suggestions please.

banny sti

iTrader: (68)

Sounds like the the lambda sensor is faulty.

banny

ZEN Performance

MAF sensor is more likely, and a slow lambda may be also contributing. A specialist should be able to tell you one way or the other for both sensors.

New_scooby_04

iTrader: (4)

Assume it is the MAF and keep it off boost till you get it checked properly!!

A faulty MAF causes fueling issues that can eaily kill your engine.

Ns04

Evo Ace

Thanks, swapped the Mass Flow Sensor with a second-hand spare and now, MUCH better, but not perfect, could it be that this one is still a bit dodgy or could it be that I need new HT leads?

Sc0oby

check for clog fuel filters

CupraDave

iTrader: (1)

You say the car is better now but not perfect, did you do an ECU reset after fitting the different MAF?

Another thing to think about, Do you have a DV fitted? when on light throttle what do you hear? does everything sound normal?

The reason I ask is I had exactly this problem and turned out to be the DV sticking open and leaking all the boost pressure, I sent it back and ended up with a new one now the car runs perfect.

The rookie

iTrader: (1)

I have had this symptom for a while (99MY) just at lower speeds (my hairdryer coming on boost at 1800), got very bad last night in the wet, pulled HT leads and they are FUBAR (track marks all over them - cheap non OE fitted by last owner), OE leads are £50.15+VAT list price from the dealer but you may get a discount.

Simon