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jopo911's Avatar
 
Join Date: Jul 2003
Location: Latrobe, PA
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Help!

Need help with my 1986 930 that has me frustrated and apparently nobody in my area that can help me. Trying to diagnose for several months now. Willing to pay anyone who can diagnose/help repair my problem:

42,000 original miles. Problem: randomly runs extremely rich for no apparent reason. Car just "stutters" and you have to rev over 3500 rpm then clears. It might be ok for minutes, hours, or days.....then it starts again. Checked about everything that can be checked; have followed many suggestions of fellow Pelicanites, but nothing fixes problem.
Have 3 bay garage with lift and all necessary tools, but need someone with more experience than me. Can anybody help me?

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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 10-02-2014, 01:54 PM
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PorscheMoparLiterbike
 
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sorry to hear Joe. I know it can be frustrating. not sure if you had other threads started. Bud maybe make another try and list everything that you've done sequentially for the brain trust to take another whack at it.
I'm a couple hours away from you in Maryland.I've done a little bit of work myself with the help of the guys here. But probably only qualified to bring you alcohol and the ability to lift heavy objects.
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88 930 BnB Kinesis tial 1bar k27/29, Turbokraft IC+blocks+rokr loks+ ported intake,edelweiss cams, KEP/Sachs, Verden Tool 38mm PP heads, ARP bolts/studs, twin plug for future
Old 10-02-2014, 03:16 PM
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I'd hook up some CIS gauges. check and denote your WUR pressures: cold, warm, boost.

Then, leave them in place. Place a couple zip ties to keep them firm and run your car [don't race it ] for enough time for the problem to replicate itself. Ensure there are no leaks at the connection points on the WUR and on the Gauge Hoses.

Then, when it happens, denote your Warm Pressure reading. I'll bet it may have dropped. If so, this could be due to a problem with your WUR Electrical Connector or the WUR itself.

That's what I'd do first...
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LIVN80S - - Red '79 Porsche 930 Steel Slant Nose Conversion [in 1987] w. 46k miles 3.3L; 964 Cams; K27HF @ 1.0 BAR, with Garrettson Intercooler; Rarly Zork; CIS Flowtech Fuel Head & BL-WUR.
Old 10-02-2014, 03:37 PM
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beancounter
 
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I'd agree that a baseline check of fuel pressures and the basic tune up list (check wires, cap, rotor) would be the first step.

Something intermittent like this sounds electrical to me. The WUR does contain a bimetallic strip that is energized with 12v and automatically adjusts control pressure as part of the "warm up cycle" although I am not sure if an intermittent loss of 12v power to the WUR would create an immediate change in the control pressure resulting in rich condition. There could be an ignition problem that is intermittent, and when it happens the combustion process is incomplete which leads to stinky gas smell in the exhaust. Smells rich, but it's not a fueling issue.

The '86 model will have the yellow square overboost relay of death in the engine comparment that gives many people problems, and I believe there are also some relays under the driver seat related to the k-jet lambda control module. Don't know much about that lambda crap since my '79 doesn't have it.

Intermittent electrical issues are tough to diagnose, especially over the Internet.

If you're at your wits end, there is a Pelican board member and 930 owner in the Pittsburgh area who is in the car repair biz. He doesn't post here much (see him in OT mostly), but might be worth contacting. His screen name is fastfredracing, says he's in Valencia, PA.
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Old 10-02-2014, 03:57 PM
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Do you still have the Lambda system hooked up and running? I ask, because I had a problem almost identical to yours, chased my tail for a couple of months, and eventually found that the engine wiring harness had a bad ground. Specifically, it was the ground that is bolted to the mounting plate for the coil. The plate had been powder coated (not by me), and was put back on without sanding spots for the ground wire and also where the plate contacts the fan/alternator housing (and the stud areas on the housing where the plate touches). After I took care of this, the problem was fixed for good. Corrosion at those points could cause a similar problem.
Old 10-02-2014, 05:14 PM
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Man, you guys always beat me to the punch. Lots of good advice, all spot on things to look for.
My bet is your WUR, or more accurately the electrical power to it being intermittent. If that bi-metalic strip inside the WUR stops heating up due to a power interruption, then you'll go pig rich when she's fully warm. Of course, we're "assuming" your issue is a rich condition. Your rear fuel pump relay is what energizes the WUR. If that relay is crapping out on you occasionally, then you'll loose power to not only the WUR but the rear fuel pump as well. Both can cause a rich condition due to lower fuel pressure (and thus lower control pressure at the WUR).
A set of gauges is a must to diagnose, otherwise you'll just chase your tail and get pissed off and driven to drink mass quantities of whiskey (which is fully appropriate....just don't get behind the wheel).
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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 10-02-2014, 05:54 PM
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Crotchety Old Bastard
 
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My money is on the Lambda system. Failure mode is rich condition.
Unplug the O2 sensor, adjust the idle AFR to 13.5:1 and never look back.
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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 10-02-2014, 06:00 PM
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Making progress

Thanks for all your advice, guys. I disconnected O2 sensor, and although it is running richer than it should be at idle (11.1), it is no longer "hunting" and is finally driveable. Question......I tried to adjust AFR with the 4mm tool, but the spring loaded shaft that the allen wrench fits in, then you have to push down on is hitting my air cleaner. Better to just remove this thing ? Looks like there is just one screw holding it on. I am assuming i need to nudge it very little counter clockwise, and hopefully good to go.
By the way.....what controls this Lambda system? The ECU under drivers seat?
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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 10-11-2014, 03:01 PM
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Quote:
Originally Posted by jopo911 View Post
Thanks for all your advice, guys. I disconnected O2 sensor, and although it is running richer than it should be at idle (11.1), it is no longer "hunting" and is finally driveable. Question......I tried to adjust AFR with the 4mm tool, but the spring loaded shaft that the allen wrench fits in, then you have to push down on is hitting my air cleaner. Better to just remove this thing ? Looks like there is just one screw holding it on. I am assuming i need to nudge it very little counter clockwise, and hopefully good to go.
By the way.....what controls this Lambda system? The ECU under drivers seat?
For the regulation of the AFR is needed one (key allen) btr of 3mm and not of 4mm. Good luck for the regulation.
Old 10-12-2014, 12:04 AM
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Thank You

Hey RarlyL8.........Thank you for your advise. Disconnected O2, and set AFR as you suggested...and wow! My car has never run this good. Fantastic! Thanks again. I have been messing with this thing for over 1 year!!
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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 10-12-2014, 01:00 PM
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The wealth of knowledge that exists about air-cooled Porsches on this forum is priceless!!!!!
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Old 10-12-2014, 01:38 PM
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uh oh

Went out to start my car this morning.....took about 15 minutes. Just would not start. Kept cranking and cranking. Finally started....Do you think maybe I went too far lean with the AFR readings? Once warmed up started every time. Set AFR from 13.5 to 12.9, waiting for it to cool off. Am I on the right track??
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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 10-13-2014, 06:51 AM
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Crotchety Old Bastard
 
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Idle mixture AFR has little effect at start up. The cold control pressure should lower the AFRs down into the 10s and then quickly raise. What was the AFR upon start up?
Old 10-13-2014, 10:19 AM
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Afr

AFR on my gauge is about 15 when initially started, then falls steadily to 13. (Since I disconnected O2 sensor) It used to fall rapidly to about 10.8, but then would never come back up and would start "hunting". Sometimes it would come up to about 12, but it would vary when you stopped at a red light, usually dropping to about 10.8, making vehicle undriveable.
What should my cold pressure be?
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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 10-13-2014, 11:12 AM
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Crotchety Old Bastard
 
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Cold pressure is a temperature dependent sliding scale. Somewhere around 20 psi would be reasonable this time of year then climbing to around 55 psi within a couple minutes.
Old 10-13-2014, 12:42 PM
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Quote:
Originally Posted by jopo911 View Post
Need help with my 1986 930 that has me frustrated and apparently nobody in my area that can help me. Trying to diagnose for several months now. Willing to pay anyone who can diagnose/help repair my problem:

42,000 original miles. Problem: randomly runs extremely rich for no apparent reason. Car just "stutters" and you have to rev over 3500 rpm then clears. It might be ok for minutes, hours, or days.....then it starts again. Checked about everything that can be checked; have followed many suggestions of fellow Pelicanites, but nothing fixes problem.
Have 3 bay garage with lift and all necessary tools, but need someone with more experience than me. Can anybody help me?
I see you are looking at this problem as fuel pressure related but I had same problem as above and it ended up being a bad CDI box. Also when I start my ''87 with oxygen sensor hooked up AFR is 10.8 at initial start then rises to near 14 warm.

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Old 10-13-2014, 03:37 PM
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