Since starting my stage zero, my car has been running much better but has also developed a cut near full throttle in 3rd, 4th and 5th gear. I would call it a stutter, but it usually only happens once or twice on the way through the rpm range, and seems to happen pretty consistently around 90 km/h in 4th. I just went out and checked to see if my turbo hoses were collapsing, but I see no indication of that. Can't replicate it at a stand still, it seems to be only under load. My air filter is newish, replaced my fuel filter after my last seafoam treatment, and replace my distributor cap/rotor/plugs when I bought the car 8 months ago. The car also has slight pinging under high load, so I plan on replacing the vacuum lines and elbows, but failing that are there any suggestions?

 

What octane fuel are you using?

 

Are you running at stock boost levels or higher?

 

Stock boost level, 91 octane fuel.

 

Sounds like fuel cut off. Is it like the car falls on its face then goes again? A big abrupt jerk.

 

Yeah thats it, really abrupt and only for a moment. Is that indicative of the fuel pump going out?

 

Boxpin hit on the head was I was going for.
I would check the vacuum lines to the turbo. Sounds like one might have broke and you are running 15.5 PSI boost as which time the ECU cuts fuel.
It is programmed into the ECU to prevent damage to the motor.

 

You both nailed it. I replaced the three turbo vacuum lines, shown in the MatthewsVolvoSite picture below, and it runs beautifully. Got a bit of the power cut in third gear two times out of five or six spirited pulls, but I can live with it. Many thanks!

http://www.matthewsvolvosite.com/ima...iagram-850.jpg

 

I was having the same issue, I then checked the wastegate settings, and set it to the stock numbers. This stopped the boost from spiking so badly and fixed the problem.

 

Boost spike is fun though! Actually the first time it happened to me, it scared the crap out of me. thanks to ARD tune, I dont have that issue anymore.

 

It was fun, but the pinging and lurching was a little concerning for my passengers haha. Today the power cut returned with vengeance, but its much less abrupt and feels more like a momentary boost cut than fuel cut. Perhaps now that the wastegate is forced to work the bypass valve has disintegrated. Any other opinions from the board members?

 

Any codes now?

 

Nope, none yet.

 

Maybe you have a slight misfire now.

 

Did a couple hard pulls on the way home from work today and didn't feel any hesitation. If this continues to be the case I am going to chalk the after effect up to long term fuel trim, else I suppose there is some more investigating in my future. Have to admit though, I do miss the mildly absurd power my car was making, I'll probably have to tune the wastegate up to 10 or 12 psi later this summer and get some off that oomph back.

 

That over powering stuff damages the motor.

 

I have no doubt that it does, as well as damaging the rest of the drive train when the ECU cuts the fuel and the car lurches like that. However, I read in another post that I can go up from the stock 6psi to 10psi without endangering the motor too much. I'll certainly feel more comfortable with it after I finish the rest of my stage 0 and am confident in the health of my engine. I would prefer to make the power through more conservative methods like the exhaust/intake/ECU tune combo, but can't see myself forking out the $1200 - $1500 to do that properly in the near future.