I have an 89 930 with SC cams, Garretson I/C, Greddy EBC set at 1 Bar, full B&B headers and muffler, and of course from Stephen at I.A. I have the modified fuel head. Makes lots of horsepower and has been running great. However starting last week, under full acceleration everthing works great in 1st gear and 2nd gear, but when I get into 3rd gear I get a stutter and miss, shift to 4th and I still get a stutter/miss there also. Sometimes in 3rd gear at full acceleration it feels like it suddenly loses about 10 percent power without the stutter. I have changed the CD unit, Coil, plugs and wires, fuel pump relays, and the fuel filter was replaced about a year ago. Anyone have any ideas where to go now??

 

What RPM does the stutter happen at?

 

Clutch slipping?

 

Overboost safety switch ? The small switch, not the large sender for the boost gauge.

 

That was my thought as well, but only if is happening at higher rpms.

 

This is what made me think it was a slipping clutch... Do the RPM's rise quickly without any feeling of power?

Brian

 

I was having similar issues that were ultimately resolved by new plugs. Mine looked like they had little bits of charcoal on the tips when they came out of the car.

 

It is not the clutch. No slipping of any kind. The stutter/miss begins at about 4000 RPM all the way to redline, then again as soon as I get into 4th, I get out of it then, no need to get into 5th..
I forgot to mention, if I let off the gas just a little, the problem goes away, however so does a lot of acceleration. I think the plugs will get replaced Monday. I'll let you know.

 

Check the distributor cap for any carbon tracking. How old are your plug wires?

 

Hi Guys.

Need help on this. I had a similar experience. It only happens on boost, 3rd gear and 4000rpm onwards. It flutters violently, feels like a power cut you experience form over revving.. ignition cut out. Only with the trottle wide open and max boost! Any inputs will be great.

 

Over-fueling problem - do you have an O2 sensor attached to monitor AFR? Check WUR fuel pressures - cold, warm and enrichment.

 

This was the EXACT issue I was having that ended up solved with plugs and a valve adjustment. My guess given the state that the plugs were in is that it was the plugs that solved the problem.

 

...ditto 930LDR repsonse. except just plugs fixed problem. it was totally amazing, felt like the car was not getting enough fuel. actually run ngk copper plugs and change them after every race weekend.

Jim -- kind of confused as you write in first post plugs were changed then, few posts down, plugs will be changed monday?

 

try new plugs, check your wires, and your cap and rotor. will it do it if your just maintaining certin rpms after a while too?? or say your in 3rd or 4th and your driving along them get into the gas some more to go up a hill under load it will sputter???

 

I know you said new wires but I had the same thing and they worked for me. Sounds like wires to me. .