Fat Boy

My car has been hesitating recently particularly when driving away from cold (especially if it's wet), but also and more alarmingly at higher revs when fully warm. The latter is harder to describe but on the weekend, 4 up, doing some spirited driving down some B roads as we were late for something it seemed to being going fairly normally, until it sort of cleared it's throat and smoothed out/ accelerated with no change from me of throttle input.

Car is P1 with full SS exhaust and ITG filter, running Optimax and NF always.

Any bright ideas, MAF, or just needs an ECU reset (did track day last Thursday at Brands GP)as it might be running rich?

On a separate but not unrelated note. Toying with the idea of taking it to the next stage ie upgraded engine control (Motec, Link, Bob Rawle type input) as I'm not totally sure that it's ever run as smoothly as it did with the OEM exhaust system, although I like the sound and generally the extra urgency with the straight through exhaust;maybe this is what is making it run a little more lumpily? Any advice gratefully received.

BrianP

I've recently noticed this too on my STI2, particularly the cold bit. Occured after fitting a K&N panel filter and filling up with Opti and a dose of NOS.

Can't say I've noticed when warm, but then I haven't used the car much since then.

STI 2, T75 downpipe & centre.

Brian

fivepint

MY standard MY00 had similar symptoms... firstly plugs were changed, big improvement, then a faulty MAF was changed (under warranty), but it defo got better with new plugs,...

Cheers

Fat Boy

my local dealer, who shall remain nameless, is not helpful with such warranty issues, so I was hoping to self diagnose it or get a recommendation for someone who would know what they are talking about to have alook at it (which would clearly exclude me).

mega_stream

Mine did this tonight on the way home. (my99)
High revs, car was warm, lost it for 1/2 a second, clearing its throat is a good description.

Mines full decat aswell, just had a full service so running 3 week old plugs..has also had a new MAF recently. Reached peak as always at 1.125 on my Defi reading 1.1 held. Warm day so can't be overboost??

Fat Boy

mega

Are you running itg or any form of induction kit. Also what fuel do you use.

I'm wondering if full decat is leaning out the mixture too much and then ecu sort of resets itself, mind you after a fair bit of high speed running on Brands GP circuit maybe its enriching the mixture a bit, if it really does adapt to driving styles. Also I'm wondering if Optimax plus NF is too much "gunk", maybe should use ordinary super unleaded plus octane booster.

John