Hi everyone, I have a bug eye with a vf34. When driving normaly everything seems fine. If I try using full power the boost drops off then comes back on again, this happens at around 4k rpm then agian at around 5k rpm, but then pulls fine to the red line holding a steady 20psi. It looks to be around a 5psi drop. Also seems exaggerated with colder air temps. Im checking all the obvious stuff i.e pipes split, hanging off but any other clues would be appreciated. Cheers Tez

 

Throw some octane booster in, if it goes it's the ecu pulling the timing.

Or like "KojaK's" car, you may be losing a lambda sensor, or even facing a MAF problem...

All just guessing of course.

dunx

 

It could be a dirty/lazy boost solenoid causing wastegate creep, as you accelerate and the boost increases the soelnoid (if a clogged 2 port) may be struggling to dump pressure away from the actuator fast enough which will cause the wasetgate to creep open early which inturn drops the turbo output pressure allowing the wasetgate to close again then the pressure builds up again and the whole process repeats until a happy medium is found.

This can also happen on a 3 port if the atmospheric dump port is restricted in any way ie the pipe is partially blocked or kinked or the internal diameter of any attached pipework is too small ie below 4mm

Cheers Iain

 

Sorted now, just a split hose. Yey easy fixes rule.

 

Which hose was split mate?

Cheers Iain

 

Mine did an actuator hose, 2 cm split in it !

 

The hose came from the manifold and went to a plastic disk type thing, not got a clue what its called or what it does.
Dunx, did you take that picture while driving lol. That must be about 30psi

 

It could have been that pipe for the MAP sensor, did it go from the manifold to the drivers side inner wing, near the solenoid?

Cheers Iain

 

no its on the front of engine. Il take a pic so I know what its called

 

It goes to the purge valve as the map sensor is in the throttle body.

 

Silly me I forgot it was a Bug

Cheers Iain

 

No ! peak recall function... I only take videos whilst driving...

Like Arf ! ( NOT ! )

dunx

P.S. Only made it to 1.85 tonight

 

OK problem is back, I have serviced the car, changed the maf, checked for more split pipes, cleaned the boost selonoid(will try this again) and the boost is all over the place again. Half throttle no issues at all but if i take the revs to 4k then try using full power my boost guage needle just bounces around and I have to gear down to speed up

 

Also can hear a srange clicking noise from around the steering colum, sounds like a relay type noise.