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NEED HELP PLEASE: Engin jurcking & losing the power around 4000 + RPM

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


Last edited by Falnaim; 06-10-2012 at 11:31 AM..
Old 06-10-2012, 10:06 AM
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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.
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Kevin
1999 911 Carrera [996]-Vesuvius Grey Metallic
Old 06-10-2012, 10:49 AM
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Thanks einsteiger
Old 06-10-2012, 10:57 AM
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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.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 06-10-2012, 10:59 AM
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Thanks RarlyL8

when I mentioned " power cutts of " dos not means (as in engine stops ) it jurcks & los the power.
Old 06-10-2012, 11:26 AM
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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
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Trond R.
1979 930: Garret GT35r turbo, EFI, carerra intake, Link EMS, custom GT2 cams, 98mm JE P/C, 964 crank (stroker), custom valves & ported (XtremeCylinderHeads) etc..etc..
1972 914-6 GT replica project
1986 944 Turbo
Old 06-10-2012, 12:22 PM
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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.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8

Last edited by RarlyL8; 06-10-2012 at 12:28 PM..
Old 06-10-2012, 12:24 PM
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Question, if you convert to long neck, do you lose the ovrboost switch?
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Old 06-10-2012, 12:27 PM
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No, the overboost switch should screw into the long neck intercooler.
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'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
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Old 06-10-2012, 12:30 PM
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I think when going to long neck overboost switch is connected on the intercooler
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Trond R.
1979 930: Garret GT35r turbo, EFI, carerra intake, Link EMS, custom GT2 cams, 98mm JE P/C, 964 crank (stroker), custom valves & ported (XtremeCylinderHeads) etc..etc..
1972 914-6 GT replica project
1986 944 Turbo
Old 06-10-2012, 12:31 PM
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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.
Old 06-10-2012, 12:47 PM
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What is BOV ?
Old 06-10-2012, 12:58 PM
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Blow Off Valve
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Trond R.
1979 930: Garret GT35r turbo, EFI, carerra intake, Link EMS, custom GT2 cams, 98mm JE P/C, 964 crank (stroker), custom valves & ported (XtremeCylinderHeads) etc..etc..
1972 914-6 GT replica project
1986 944 Turbo
Old 06-10-2012, 02:07 PM
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Quote:
Originally Posted by Tt surgeon View Post
Question, if you convert to long neck, do you lose the ovrboost switch?
you don't happen to have a pic do you?
c
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Old 06-10-2012, 02:11 PM
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When rebuilding, is there any chance that you swapped the two vacuum hoses to the pots on the distributer?

Rod
Old 06-10-2012, 05:49 PM
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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.
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RarlyL8 Motorsports / M&K Exhaust - 911/930 Exhaust Systems, Turbos, TiAL, CIS Mods/Rebuilds
'78 911SC Widebody, 930 engine, 915 Tranny, K27, SC Cams, RL8 Headers & GT3 Muffler. 350whp @ 0.75bar
Brian B. (256)536-9977 Service@MKExhaust Brian@RarlyL8
Old 06-10-2012, 07:51 PM
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Quote:
Originally Posted by Tt surgeon View Post
you don't happen to have a pic do you?
c
Post #9 pic #5 of this thread -

Sticky for common answers to why "My car doesn't start...."

Last edited by Ronnie's.930; 06-10-2012 at 10:51 PM..
Old 06-10-2012, 08:03 PM
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I'll try to find it and link it here.

Last edited by cuchanonM; 06-10-2012 at 08:29 PM..
Old 06-10-2012, 08:26 PM
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Thanx!
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'07 997.1tt
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Old 06-10-2012, 09:05 PM
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Problem Solved

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

Old 06-26-2012, 08:45 AM
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