NEED HELP PLEASE: cutting of power around 4000 + RPM

[Falnaim]

Hello There,

I have 1987 930 turbo just rebelled the engine and have new Alternator, Fuel pumps, Alternator Fan, Faabspeed "Headers, Mufflers, Air Intake, Intercooler", Tial W/G with a 1 bar spring, A/C kit.

When i drive the car Engin jurcking & losing power after around 3900 to 4100 RPM then i replaced the Distributor Cap, Ignition Wires & the Coil Wire with new set and still having the same problem but "more power with engine" as 2 of my Ignition Wires was broken.

Please can any one help me what to do ?

Thanks and Best Regards,

FAHAD

[einsteiger]

I recall a very similar situation with another 930, but I cannot remember on which forum I saw it!

I'll try to find it and link it here. This person also had to deal with power falling off after 400 RPM.

[Falnaim]

Thanks einsteiger

[RarlyL8]

I'll throw in a few suggestions even though you used the F word, ha!
HOW does your engine falter at 4K? Teeth in glass, bucking, or slow power loss?
> Teeth in glass - overboost switch activated
> Bucking - fuel pump, ignition
> Power loss - BOV, fuel pump, O-rings
These are generalities, need more info to hone in on it.

[Falnaim]

Thanks RarlyL8

when I mentioned " power cutts of " dos not means (as in engine stops ) it jurcks & los the power.

[totle]

Sounds like the overboost switch is failing. Had similar problem on my previous 930.
You can test by connecting the wire to ground and try. If all is good then, you need to replace the overboost switch. It is located under the IC in the BOV housing

[RarlyL8]

Bucking/Power Loss - check the easy stuff first, O-rings and vac leaks.
> Check timing / ignition function
> Check fuel system pressure and flow
> Factory BOV? Pull and check gaskets and piston

Kevin may have seen my post last week on the failed BOV. After replacing the gaskets I was not expecting the piston/spring to be hanging up in the bore but they were due to oxidation of the surfaces. The symptoms I had been experiencing were bucking and loss of power at full boost.

[Tt surgeon]

Question, if you convert to long neck, do you lose the ovrboost switch?

[RarlyL8]

No, the overboost switch should screw into the long neck intercooler.

[totle]

I think when going to long neck overboost switch is connected on the intercooler

[JFairman]

I've experienced that when it was getting too much fuel on boost. I have the Brian Leask adjustable WUR or control presure regulator and it needed boost control pressure raised a little bit to fix it.

You need a wideband air fuel ratio gauge or control pressure gauge on board to diagnose that.

[Falnaim]

What is BOV ?

[totle]

Blow Off Valve

[Tt surgeon]

Originally Posted by Tt surgeon

Question, if you convert to long neck, do you lose the ovrboost switch?

you don't happen to have a pic do you?
c

[908/930]

When rebuilding, is there any chance that you swapped the two vacuum hoses to the pots on the distributer?

Rod

[RarlyL8]

Swaping vac ports on the dizzy won't make any difference when on boost. Both ports connect to the throttle body just in different locations, above and below the throttle plate.

Jim getting too much fuel on boost is not a typical situation, they can choke on the midrange of a stock engine with a failing WUR. This engine is modified so I would expect it to go lean. Good point on the AFR gage, great tool needed in this situation to help see what's going on.

[Ronnie's.930]

Originally Posted by Tt surgeon

you don't happen to have a pic do you?
c

Post #9 pic #5 of this thread -

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/547032-sticky-common-answers-why-my-car-doesnt-start.html

[cuchanonM]

I'll try to find it and link it here.

[Tt surgeon]

Thanx!

[Falnaim]

I replaced the Over Boost Switch And Or Pressure Sending Unit For Turbo Boost Gauge.
Parts Number:-
930-606-101-00-M100
993-606-103-01-M100

My car is working now perfectly .

Regards,


FALNAIM