scoobystan

when accelerating hard in my car i.e full throttle, my cae has an annoying tendancy to stutter!! u can hear the exhaust sometimes 'pop' so to speak and i have no idea what is causing it.
Trying to pull away hard from cars or when a drop a cog to overtake is annoying as it keeps stuttering between 3-5000rpm before dying and clean acceleration is eventually found, if i am in the troodos mountains using low gears and lots of twisty rds, hairpins etc it is even more frustrating as it is not clean in accelerating. it has not long had a 60,000mile service and no faults were picked up on the computer!!
anyone any ideas PLEASE IM LOSONG OUT ON VALUABLE FUN HERE!
MANY THANX STAN

rik1471

Try relaxing and taking deap breaths. It's probably due to the excitment from the acceleration.

Catalunya 051

Sounds to me like your car is overboosting and the fuel cutoff is activating to save it from detonation, then when the revs get higher the boost is dropping to safe levels and you are getting un-interupted fuelling.

LG John

Whats that then?

D8UGF

Gggget ittttttttt ffffffixed then!!

Catalunya 051

What? A safe level of boost? Depends on the setup of your car doesn't it Saxo.

LG John

TEK3, full decat, dawes at 1.25 bar on an MY99. In 5th at say 70mph if I floor it the car doesn't alway pull smoothly with very slight juddering....I wondered on the basis of your comments if this was something to do with fuelling? Its never really severe and I don't worry about it.

john banks

Nothing wrong with your fuelling Saxo. None of them are BMW smooth

LG John

Yours was.......once

Jaay

I have those exact same symptoms, im trying the new coils and plugs approach. The rubbers that cap the Plug head were perished/split/missing completely ! on 3 of 4 leads so I thought I might try the Oz Bosch coils with new plugs and leads. Still have to get round to doing it probably the weekend though. Ill let you know how it goes.

scoobystan

nice one bud, at least some one gave me a decent reply. for your info my car boost peaks at 1.1bar at 5500rpm, i run a custom backbox, apexi induction kit, have not really started modding engine yet as i have been concentrating on the styling. I plan to go down the route of, lightened flywheel, semi-racing clutch, i can get my ecu remapped by prodrive for 800notes due to an agreement between subaru cyprus and prodrive, then change my hoses for samco items. nothing too brash just a little more so i can keep up with my mates modded stiv5, then for handling i will go for bilstein shocks, uprated springs, sti stabiliser kit, anti lift kit etc. finally to stop it a 4 pot set up, up front and black diamond rear vented, drilled/grooved discs with mintex pads-my mate has this brake set up and it is amazing!!
cheers bud
stan

BruceWarne

Dumb question, but have you tried using some injector cleaner?

Catalunya 051

Stan, the four pot brakes (OE ones) are a good cheapish improvement, but watch out with drilled disks. A lot of people on here have had disks cracking because of the drilled holes, especially on track days (if you do them). Cast disks with holes don't tend to do this as the holes are not a weak point like drilled ones (drilling causes stress which in turn weakens the disk). I use grooved only and they work just fine, they clear gas between the pad and disk just as well as drilled disks. I have Tarox G88 (40 grooves) and they still look pretty good, and work great with the 4 pot OE callipers.

wirerob

This may be a daft question, but when checking my coil packs due to a missfire I noticed 2 of the rubber tips were perished and cracked. I taped them up with insulating tape and the missfire went away - so can you just buy the rubber tips on there own as this must be a cheaper alternative than paying £50 per coil pack.

Catalunya 051

Saxo - There are lots of other threads, mainly about the Dawes device that mention the safety cut out on the fuel supply that comes in when you get too much boost for the engine to be able to keep the fuel/air mix rich enough to avoid detonation. The values of boost banded about are 1.21 or 1.22 upwards where the fuel is cut off by the ECU to safeguard the engine. Most people set the boost to between 1.1 & 1.2 to allow a bit of "headroom" for the extra boost you get on cold wet winter days. I believe the only way round this (safely) is to put larger injectors that can supply more fuel to keep the fuel air mix rich enough at higher boost levels and to re map the ECU accordingly.

LG John

I run 1.25bar but the Tek3 remap should more than take care of any fuel problems should it not. There are peeps running upwards of 330bhp on standard UK internals before thinking about injectors, etc?

trance

Scooby stan,

I had the same probs with mine hesitating when accelerating. Anyway, was found to be just slightly overfilled with oil. The oil was getting in to the boost pipes. Just a thought with you just getting it serviced and all. Seemingly it just has to be a ball hair above the full mark to cause this.

N.b had it dignostic checked and no faults showed up.

[Edited by trance - 10/10/2002 1:03:28 PM]

john banks

You won't max out injectors with a TD04L. The limit on boost is detonation from excessive back pressure and charge temperature from the small turbo at excessive boost.

ShAnNo_RB5

Had a similar problem with my STi V2 about 2 yrs ago - took it to Power Engineering and they fitted new coils and spark plugs... Hey presto, problem solved!

Mind you, I guess it's a fair trek from cyprus to PE right?

Shanno

dowser

With dawes/td04/ppp ecu at 1.3 bar I hit 96% idc

Any ecutek remap will, of course, reduce that considerably

Richard

shunty

ditto the comments about new plugs & coil packs to cure the stutter....
worked on mine.....very smooth now, turned up the boost a bit as well now @ 18psi in 4th & 19 in 5th...

shunty

Forester_GP

Stan, have you checked your boost pressure while being at some high altitude? it could be fuel cut because i've seen (on DD)the relative boost pressure going up when the atmo is going down and this is determined by the altitude and weather conditions. At 500m above sea expect a steady 0.1 Bar increase on Manifold pressure but also expect spikes up to 0.2 Bar (specially on 3rd gear)which will push you well into FC territory. It looks to me that the ECU tries to maintain absolute pressure (boost + Atmo) but the fuel cut is based solely on Manifold, maybe John or somebody else can verify.

Regards,

George

Gez

Maybe its just as well its stuttering at Troodos mountains! Ive been up there and some parts are scary to say the least, especially when there is nothing between you and a 1/2 a mile drop. :-)
Appart from that its true that the higher the altitude the less boost you will need to run in order to prevent fuel cut.
I whent driving up Trodos mountains a year ago in a friends EVO 6 and i found the car to be stuttering after and during sharp bends. The problem was later diagnosed to fuel surge.

Gez

MikeSTI7

I have this problem between 3000-4000RPM but only with medium throttle long gears.I have a Pod fitted so tried the standard airbox and problem was solved, my uneducated guess is the MAF is getting a bit confused.

scoobystan

i shall get my coils and leads checked out, anyone running after market leads out there or oe items?

scoobystan

also how many coil packs does the scooby have, p.s i may be listed as scoobie newbie but ive been driving me car for a year plus im a fast response trained dvr!! good course. done some other bits with my job which cant mention due to having to reveal what i do for a living. sorry!!

Dario

I had a similar problem - turned out to be sparkplugs

Regards

Lee