Good morning folks, recent issue, 1997 850 AWD Turbo 5 speed, when I accelerate hard under boost I am getting a hard "stutter"..... almost seems like the engine is cutting out for a split second a couple of times in a row.....

I know, hard to explain it in writing but I hope somebody recognize the symptoms of a know issue.

The car runs great and I only have this problem when I push it past about 5psi of boost, any guidance would be appreciated.

 

It sounds like you're hitting a limit in the ECM or ignition failure.

Is your check engine light (MIL) working and is it on ??

 

These cars have a built in fuel cut off at 15psi. Engine will abruptly shut off indicated by a big jerking sensation

 

Hitting the rev limiter is a good guess but it did not do this before, engine was smooth and lots of power under boost, just started doing it with no changes to anything.....

There are no dash lights on and no OBDII codes.........kinda stumped on this one.........

 

I thought about that but I am not near 15psi when it happens, seems to be between 5 and 10psi it shudders and stutters........I have an aftermarket numbered boost gauge.........

 

Does the stutter happen in all gears and is it more pronounced at the higher RPMs ??

 

Yes it happens in at least 1st 2nd and 3rd..... I let off the boost at that point.....

I will check RPM level, I was watching the boost level instead.......

Perhaps I got a crappy tank of fuel or..........

 

I take back ignition as if it was an ignition problem it should set a code for a misfire and or multiple misfire.

 

i know im late to this thread but this is mainly for other people that might stumble upon the same problem.
the 850 awd is "lpt" meaning light pressure turbo lpt cars have a boost cut at around 6psi some cars i have seen with 7psi, if your bypassvalve and boost solenoid vacuum lines are old your ecu most likely thinking youre over boosting the car. Samething happened in my 850awd sometimes because i had tightened the wastegate a little bit so it would build boost even faster and boost a little bit more. Also a more free flowing exhaust and a sport cat will make the car boost creep which means that the turbo is able to flow out more exhaust gasses because there is less restriction which in turn makes it build boost better, easier and more. There is really no ther explanation for it that i can think of.