matty01

UK MY98, full de-cat but otherwise standard,running optimax...[pet theory]i think it *may* be running lean[/pet theory],main symptom is lack of power when holding a steady throttle and THEN flooring it ,but only when allready in rev range where boost can be made ,if i then change up all is ok again[it does it most when hovering at 3000rpm ready to overtake, then gun it and low power ] ,if i let the revs rise from below ,say, 2000rpm past 3000rpm and onwards it'll allways make full power(seems like low boost pressure,but i've no gauge)it seems as though the car is backing the power off because some safety parameter has been passed,(but i'm only guessing)It will not do it every time but once or twice on a 15 min backroad trip.The other thing that made me think it may be running lean was that it doesn't pop and backfire all that much [pretty rare]and as i understand it that is due to unburt fuel ,my pet theory goes that if it's running lean there may not be enough unburnt fuel to cause this.
Anything you can rule in or out would be appreciated,thanks.

Timmy2004

I've got a uk my98 turbo with full de-cat and mines done just the same in the same sort of situation. i checked my guage at the time and it was only running 0.5 bar (Half boost basically), don't know the reason yet but will try & find out....

TonyBurns

iTrader: (3)

You could be overboosting, it wont be the emissions because i dont think MY98's had this one the ecu.
Does it hesitate when accellerating in gear (around 4k rpm seems to hit a bit of a wall??)

Tony

matty01

re: wall at 4k,hard to say, nothing obvious ,maybe a little hesitation but only slight if at all.
re: overboosting,when i gun it there's less power straight away it doesn't seem to be normal for a split second and THEN held back,would this fit the profile of overboost(is overboost corrected by fuel cut yes/no,please? )
Q. Is it mainly the ecu that marks the my98 apart from pre-98 and post-98 cars?

[Edited by matty01 - 1/9/2004 7:06:35 PM]

easyrider

It does sound like the classic"emissions holdback"-and it was on the MY98 ecu-it used to do it on my old MY98-i got over it by fitting a Dawes Device, and it made a world of difference knowing that it would get full boost after holding revs for a few seconds.

When i had it happen to me, i had all the same questions as yourself-all turned out to be "normal".

easy

easyrider

I forgot to add-the "emmissions holdback" cuts boost to about 0.5bar-an other way around it is to release the throttle briefly as if you were changing gear(after youve been holding circa 3K revs) and then floor it-it feels pretty weird doing it this way having to take your foot off the throttle to get full power.Or you can just change up a gear.

easy

matty01

Thanks all looks like a dawes and boost gauge and afr then ,cheers.