Acceleration Problem - Fault Diagnosis Help Please!

driveforward

Is at the Nürburgring
Nov 5, 2002
3,245
0
www.driveforward.com
Cordy has a bit of a problem when accelerating hard using the full rev range, which is generally only apparent in 2nd and 3rd (prob more due to the nature of my acceleration than anything else)

Let's say I accelerate to 4K revs in 2nd before changing up to 3rd, when I've changed up and reapply the accelerator, there will be no acceleration for a few seconds, then it kicks in. During this time it's as if the engine isn't pulling, and it's being retarded. Pressing the accelerator doesn't increase the revs by much at all during this time, and there is no boost from the turbo.

After the few moments have passed, normal operation is resumed.. until let's say I then rev in 3rd in the 3-5K range and change to 4th.. where the retardedness returns again.

It seems as if the engine goes into a 'limp mode' momentarily after being in the higher rev range following a sudden easing off the accelerator.

There are no fault codes logged whatsoever.

Any clues?
 

devonutopia

fabia-lous
Mar 30, 2004
1,200
1
Exmouth / Exeter
Almost sounds like the worst turbo lag ever, eh? Well odd! :(

Could it be the boost sensor being intermittent? I'm cr4p at trying to be mechanically minded, but this might be killing the boost momentarily. Thought that might have logged a fault though - some kind of intermittent fault log.
 

muddyboots

Still hanging around
Oct 16, 2002
5,739
1
Just checking, you never know, sometimes the obvious things go overlooked....(you have got fuel in the tank haven't you ? ;) )
 

m0rk

sarcasm comes free
Staff member
May 19, 2001
27,787
33
Clanfield, UK
driveforward said:
Definately not, the engine seems lacklustre, nothing like clutch/transmission

Did you drive a petrol & now got back in yours?

only kidding.

do check the req vs delivered boost

log the MAF to make sure it rises...
 

basstard

Dropping Cogs is Useless
Aug 24, 2002
2,746
0
Roma, Italia
Visit site
Anytime pal,,,

btw, if you log the data, vagcom will do it in .csv format [comma separated values] and you might want to use the data in excel. In this case you'll need a csv to xls converter, there's quite a good bunch of'em around, just have a search on google.
 

driveforward

Is at the Nürburgring
Nov 5, 2002
3,245
0
www.driveforward.com
I wasn't giving it full on acceleration at the time, and I think I experienced it going from 2nd to 3rd (my memory is crap btw!), so I'd say it occurred at just after the change at 412.3s which looks to me like a 1st-2nd change; or 417.47 which I think may be a 2nd to 3rd change. The actual and requested boost at these occasions does seem to buck the trends, and both in a different way - which would tie up as the 'phenomenon' only occured the once.

I also logged MAF data and injector quantities. Does anything 'stand out' as a problem to anyone?

Ian
 

Niall

Active Member
Aug 6, 2003
880
0
www.testrake.com
Try swapping the N75 and N18 valves around. thes should be on the innerwing somewhere. If the fault goes away then your N75 is fecked