At full throttle, in 3rd gear and up, once the revs get to 4500 or higher, it will have a sudden loss of power, the revs will climb very slowly it feels like a misfiring or stuttering, like its starving for fuel. Its fine in 1st and 2nd gear through the rev range. But 3rd and up once the revs get higher it happens. When it starts to stutter the boost will usually drop from .6 or .7 down to .4 and stay there. NO check engine light, no trouble lights at all. The car is all stock, No mods.

I have already done a boost leak pressure test up to 15psi, and its fine. I have installed new bosch fr6 plugs and updated 997 coil packs.
I have removed and visually inspected and cleaned the MAF, I havent replaced it because from what ive read, when they're bad they turn on psm and abs lights.

Last month my durametric told me p1136 Fault code 440 pressure sensor signal comparison charge pressure/ambient pressure signal implausible. I cleared it, and it hasnt come back yet. I checked the faults yesterday and it said misfires on 4,5 and 6, I cleared them and took it for a test drive and they havent come back yet. But the problem still persists.

Only at higher rpm (aprox 4500 and up) while accelerating it feels like the power is cutting out, and the rpm's increase very slowly. During idling or normal driving its fine. If I floor it in 6th gear at 60mph it will hold .7 bar and accelerate like it was new. The problem only happens at higher rpm.

I removed and inspected the stock DV's and they seem to look and operate fine while applying vacum, but Im no expert.

Please help

 

I still think its plugs or coils... something may be loose.. like a plug...
are you using race gas? meth?
How much boost you running
markski

 

The car is all stock, the most I ever see is .7bar. I use premium pump gas, 91 octane is the highest I can get here.

I had this problem before I changed the plugs and coils, and after changing them the car still had the exact same symptoms. So that keeps me thinking its something else.

 

Variocam?

 

new fuel filters?...you also could have a bad injector or a hairline crack in the plugs that are mis-firing (4,5 and 6)

 

How did you do a boost leak test? from? throttle body? Turbos?

 

Are you getting any codes? Read them if so and see if it is on one cylinder or a bank, etc.

 

Every time I had or heard about a "breaking up" problem on the air-cooled 911 Turbo's, it was spark related. Voltage regulator being the most common issue...FWIW

 

Thanks for all the input guys.

Is there a way I can test the fuel filter with out buying one?
What should I do to either rule out of blame the variocam? Reset??
Is there an easy way to check the injectors?

To do my boost leak check I removed the airbox and tested it right there where that first hose clamp is. So I have checked everything between the MAF and the engine.

There are currently no codes, I erased them yesterday (misfires on 4,5 and 6), and after a agressive 10 minute drive that caused it to act up and surge or misfire several times, when I got home the codes had not come back yet.

When I replaced the plugs I checked all the gaps, they were all slightly larger than the recomondations I could find on these forums, but I had also read somewhere if it was close to leave it. Could this be my problem, even though it drives exactly how it did before I changed the plugs??

 

Bad gas?

 

Larger than recommendations? Gap is very important, even on a stock engine. What was the gap before and what is it now? Are you overboosting at all?

 

What is the correct gap for the Bosch LDC FR6's?

 

Unbelievable...right out of the repair manual...

 

Have you tried cleaning your MAF?

 

I have had this same issue with over 3 tanks of fuel from different stations, so I havent put much thought into bad gas. I have never seen it overboost. I will go check the plugs, I cant remember what they were, just that it was a litter bigger than the recomondations I could find, I used the preset gap from bosch.