As I accelerate, boost comes in strong as normal, then every 200 rpm it backs off, then comes in, then backs off; cycling 4 or 5 times up through the revs

Any ideas?

MY99 full Scoobysport system + remap

 

Overshooting its boost target.

Sticky actuator, sticky solenoid valve, duty cycle too high for conditions etc. What boost does it peak/hold? Is it worse in higher gears?

 

John

Thanks for quick reply

I haven't got a boost gauge, so I don't know what peak/holding boost is.

Yes, seems worse in higher gears, perhaps just more noticeable as there isn't time for the cycle to develop in 1st, 2nd. In 3rd, 4th, 5th however, testing it from say 2500 up, it's very noticeable.

I'm no expert, but I'm up for basic DIY - anything I could try?

 

If it's none of the above, it might also be a pressure leak in the system.

Check all your hoses/hose clamps are tight and seated right.

I had a similar problem but the solenoid was fine etc. etc. I checked everything.

In the end I noticed the jubilee clip on the hose from the intercooler to the throttle body looked tight but was actually broken - it would turn and turn but not get any tighter. Replaced this and the car was fine!

Not saying this is your problem but it's another thing to look at.

Rich

 

Thanks, Rich

I'll check it all out as soon as I can....