I have a MY00 uk turbo with apexi AVC-R boost controller and S-AFC fuel controller.

In recent weeks my car has started to hesitate and judder back and forward when im around 4000 RPM with light throttle. This happens in every gear. I have switched off the boost controller and have noticed that the car is only giving around 0.5bar boost without the controllers intervention (Shouldnt this be around 0.9?).

Do you have any ideas as to what could cause this and if so where i can source the relevant parts?

thanks for your help

Dale

 

iam having similar probs sounds like coil packs best get confirmed before u splash out £200 tho!

 

If you switch the boost controller off the boost will be governed by the wastegate actuator spring pressure only which is around the ~0.5bar mark.
Does the car still hesitate with the boost lowered - with the boost controller switched off?
The hesitation does appear to be ignition/spark plug related and will become increasingly noticeable when the boost is increased.

Cheers

 

If i put the boost controller on i get about 1.15 bar of boost and no juddering after 4500 RPM, it only occurs at 4000 RPM and light throttle.

Sounds like i'm looking at either the Lambda sensor or the coil packs then?

 

Delboy,
i thought with the boost controller off it would revert to standard boost which is around 0.9-1.0 bar i think on MY00. Is this not the case?

 

Wwitching the boost controller off will cause boost to be passed direct to the actuator rather then bled off via the boost control solenoid. The standard setup also uses a boost control solenoid driven from the ECU, but your boost controller probably uses it's own and has bypasssed the standard setup.

The cracking pressure for the actuator is about 8psi, so that's all you will get with the solenoid switched off or bypassed.

 

OK thanks for that info. It was obviously just a side effect of me trying to isolate the 4000 RPM thing and not enough knowledge

That still leaves the problem that it is going nuts at 4000 RPM, any suggestions about that?

 

Could it be MAF ??
Have felt similar thing in an MY99 scoob stuttering/hesitating at 3600rpm through to about 5000rpm, it was diagnosed as a faulty MAF.

 

If it was WOT hesitation, my money would have been on MAF as well. But as it's part throttle, I'd be thinking lambda sensor. If you perform an ECU reset (using the plugs and not the stupid "battery disconnect for an hour" method), if the CEL flashes within a few seconds of reset-driving, it probably isn't the lambda. If it takes ages to flash the all clear, or indeed if it flashes you a code 32, then I'd be phoning my local Motor Factor...