Drivin' me nuts! please help!

[mr_angry]

Hi - Newbie here needs some help!

My '88 golf gti 8v digifant (pb engine) with 85k miles is a bit sick - when driving, she just wont rev over 4900 rpm in 4th and 5th gears. Revs freely enough when stood, and drives ok through the gears - maybe a little flat compared to my previous gti's, but generally ok. Idles fine too. Just lacks top-end power.

Up to now, I've replaced plugs, leads, dizzy cap, rotor, coil. genuine vw temp sensor. I've checked for air/vac leaks, cleaned out throttle body with carb cleaner. Added several doses of treatment to petrol. Checked timing, had mixture and idle speed set up. Replaced air flow meter for a second hand one off ebay. Generally, car seems fine, only other symptoms I've noticed are mpg on trip computer shows 99.9 most of the time, occasionally dropping to 80, and the car does seem a little heavy on fuel consumption. I'm a bit stuck now, and need help as it's driving me that mad, i'm considering getting rid. Anyone point me in the right direction?

Cheers.

[rubjonny]

For a start it like you have a vac leak from the pipe to the clocks, its probably popped off at the back.
Next I would double and tripple check both the static & ignition timing, mine never ran right till I got this spot on!
Have a look at my digifant tuning post in the MK2 maintenance & info section

[Veedubgt18v]

check your vacuum hoses in the engine bay to, and your intake pipe could have a split aswell. this is definately pointing in the direction of a vacuum leak of some kind

[mr_angry]

Cheers - for the replies - have double and treble checked all hoses for wear and tear/leaks - can't find a thing anywhere

One thing I did notice is the big hose that runs from the ISV to the throttle body feels very weak, although not holed or split anywhere - wondered if this could be sucking itself closed and if that would cause the problems? although I thought I would have a dodgy idle if that were the case? anyone?

[Diluxe]

Did you manage to get the bottom of your problem?

[Mr Blue]

i doubt its your isv.

I have read on this forum that you can use a mk3 gti relay to make the engine rev slightly higher or something?

I had my relays in all wrong and the engine didnt run well. possible your relay/ throttle switch no?

[VeeDubGTI16v]

is that like one of those relays off ebay