Got a my99 RB5, standard apart from PPP,Blitz nur spec and Sti panel filter.

Basically the car is overboosting to 1.4 bar and only seems to happen when the car has been driven for a while and when red hot, 5 gear is worse as the boost shots right up when i put my foot down then fluctuates off then back on again, you can actually feel the boost come in fits and spurts.

Have actually had this occur to me before when one of the inlet manifold gaskets had split, so far the car has a virtually had all new boost pipes the ones that haven't have been checked for leaks, changed the boost solenoid, dump valve and had the inlet manifold off again to see if it was the same problem and they were fine.

so any suggestion would be much appreicated
Thanks Chris

 

Check the arm on the actuator on the turbo. I heard they can come loose.
I always get dawes type manual boost controllers for all the trubo cars I've had, just to cap to boost to avoid overboost.

 

have you taken any cats off? and is the restictor pill in the new boost pipe from turbo outlet nipple to the tee piece the correct size 1.2 mm i think but maybe diffrent with ppp, mine did this as soon as i put fre flow airfilter onand de cat centre cat (normal airfilter fitted now)

 

No cats off, and restrictor pill was placed back in, i actually replaced all the pipes when i had this fault the first time with the manifold gaskets, and the problem has come back about 6 months later!!!

 

as joey turbo says cheak actuator arm may be for sticking or may have been wound up a bit to get more boost cheak that too,hole needs to just go over the pin if you have to pull the arm to it a long way it may of beenwound up

 

I've had the car 3 years and it's only just started doing it last week, i had this problem before and turned out to be the inlet manifold gaskets, but already checked them, got some grips on the actuator arm and comes out ok then springs back, any other ideas????

 

tee piece btween actuator is correct way round? i did it wrong and just for that i got over boost also is new pipe work has to be ome or correct size, mine did exaclty same on motor way in 5th boost up n down spent ages trying to fix but resorted to dawes device to fix it but i had taken a cat off though but now it has been mapped so all is fine

 

Well the CEl light came on tonight and plugged it into the select monitor and low and behold finally found the problem!

Knock sensor.

Only plugged it in a few days ago aswell and nothing came up, so that now explains the retarded timing and overboost, thanx for your help though guys.