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jopo911's Avatar
 
Join Date: Jul 2003
Location: Latrobe, PA
Posts: 108
"Stuttering" problem with '86 930

I suddenly experienced a "stuttering" problem with my '86 930. 39,000 miles. Kokelyn intercooler, European Fuel distributor, K28 turbo, cold air intake, GHL single out exhaust, GHL headers with heat. Car ran perfect when I purchased a year a go, then all of a sudden it started hesitating seemingly at lower rpm. I noticed the turbo bar gauge "goes crazy", and it feels like something is holding the car back. I thought it may be the fuel pump fuse issues, and , sure enough, my fuse panel was black and burnt, so I did the modification and separated the 2 fuel pumps with separate fuses, but this did not help. I also checked all the pressures, they are all right on.
I did always notice that the car runs "rich". Even upon start up, the exhaust is very black, and always starts idle at 900-1000rpm. It never runs faster and then idles down, always one range. If I try to warm it up by gently using accelerator pedal, it will run rough for about 30 seconds, then smooths out. I checked the aux. air valve, froze it, and then heated it, it is working fine. I am stumped as what to look for next. I have had several SC's, and was able to figure out any problems, but this has me baffled. Sometimes it runs perfectly, but it is a hit or miss proposition. Any hints on what I could look for?
Thanks!

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Joe
1986 Black on black 930
Kokeln IC/ 1 bar spring/European Fuel Head
GHL Exhaust Dual Exhaust, Wevo shifter and coupler
935 Front Air Dam, Forgeline wheels
Old 03-08-2009, 06:13 PM
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OFF THE BOOST PIPE NOW...
 
A930Rocket's Avatar
 
Join Date: Oct 2003
Location: Mount Pleasant, South Carolina
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CHANGE your spark plugs, check your plug wires, cap, rotor, fuel filter.
Old 03-08-2009, 06:16 PM
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Check the intercooler and turbo air pipe o'rings and any other rubber couplers for the turbo air. If you've got a bad air leak as a result of a bad seal, all sorts of funny stuff happens. It will mess with your vacuum, and it will mess with your mixture AFR's.

In my earlier learning days (preliminary, as the learning process never stops and I always find that I know a crap load less than I think), I "over-boosted" once and got to experience that freightening emergency fuel pump shutdown (thought I blew the motor up). Afterwards, it ran like crap...because all that boost and jarring the engine around dislodged an o'ring. The car would not idle without my foot on the gas, would not boost above maybe .4bar (duh!)...stuff like that.

If your fuel control pressures are all ok, then it shouldn't be WUR related.
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Mark H. 1987 930, GP White, Wevo shifter, Borla exhaust, stock everything else. The result of a massive Pelicanite good will fire recovery effort. Truely an open book, ready for the slippery slopes to modification.
Old 03-08-2009, 06:34 PM
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I would first check all seals, hoses and intake gaskets for leaks. Also, what about getting your fuel injectors flow tested?
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87 930
96 BMW M3 Coupe
89 951
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Old 03-08-2009, 07:07 PM
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YUP, you've got a vacuum leak somewhere for sure,, sounds like a big one..
Get yourself some carb cleaner, when it's idling,, spray around the injectors, intake etc,, see if you can find somewhere that will make the rpm's jump, there's your leak.
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98 Tahoe ,2007 Saturn Vue
86 930 black and stock, 80 930 blue tracdog
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Old 03-08-2009, 08:20 PM
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Dave 86 930 Fl's Avatar
 
Join Date: Dec 2005
Location: 1000 Islands NY
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I would do the following:

1 - Replace the fuel pump relays & fuses with new units whether you think they are needed or not.

2 - Put a CIS gauge on the engine and verify system and control pressures are within specs. Also verify warmup cycle is correct.

3 - Check for vacuum leaks

4 - If no luck with items above, buy a copy of Porsche service manual.

Regards, Dave
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1986 930 - K27-7200, Andial Intercooler, Tial Wastegate, Electronic Boost Controller, B&B headers, Bodart Zork, Leask Adjustable WUR, Full Elephant Racing Suspension w/Adustable Spring Plates and Von Shocks, Wevo Transmission Mounts, Fuel Safe Fuel Cell, Forgelines (9"/11"), Hargett Shifter, Innovate AFR, Cobra CF Seats, DAS Rollbar, Coleman Floating Rotors, Lightweight Interior, Forgeline 17" x 9"/11", 2800 lbs.
Old 03-09-2009, 02:36 AM
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I had similar issues with my '87 a few months ago. Mine would break up under high load and boost but drove normally most of the time, on one trip it was bad enough to feel like a steady misfire and I decided to park it. To correct it I ended up replacing the plugs, distributor cap, plug wires, and rotor. I also replaced the vacuum line running to the waste gate and sealed all other vacuum connections with new lines and tie wraps. I then removed and replaced the seals on the intercooler (mine is a B&B). It runs much better now, good smooth power all the way to redline.

Here is my thread, Breaking up and stumbling under boost
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1987 GP White 930
1977 Ford Bronco

Last edited by willtel; 03-09-2009 at 05:40 AM..
Old 03-09-2009, 03:23 AM
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930s rule the wasteland
 
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Any of you guys ever try pressurizing the intake system off thefuel meter to look for leaks with regulated compressed air?
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1980 930 Turbo
1993 Corrado
1983 944
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2001 VW golf TDI
Old 03-09-2009, 04:10 PM
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I have.

I went to home depot and found some pvc fittings that fit inside the elbow going to the air meter. I then drilled and taped the fittings for a 1/4 inch npt fiting.

Hooked up a small air regulator and checked for leaks.

I found my overboost switch, the injector blocks, intercooler, and the throttle body all leaking air.

I ended up mixing up some really soapy water in a spray bottle and lightly missed the engine until I found some bubbles.

There are new professional systems that use smoke (by burning baby oil) to trace for air leaks.
Old 03-09-2009, 04:25 PM
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I like your theory. Could you elaborate on how to do this?
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Joe
1986 Black on black 930
Kokeln IC/ 1 bar spring/European Fuel Head
GHL Exhaust Dual Exhaust, Wevo shifter and coupler
935 Front Air Dam, Forgeline wheels
Old 03-09-2009, 04:26 PM
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930s rule the wasteland
 
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very cool, im gonna try to do mine tomorrow, what pressure do you regulate to? 1 bar or less?
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1980 930 Turbo
1993 Corrado
1983 944
1984 944
2001 VW golf TDI
Old 03-09-2009, 05:09 PM
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Quote:
Originally Posted by jopo911 View Post
I like your theory. Could you elaborate on how to do this?
Please do. I can only imagine that I didn't get all my leaks and I hate the thought of leaving power on the table.

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1987 GP White 930
1977 Ford Bronco
Old 03-09-2009, 06:48 PM
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