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smart931 · Posted: Sun Apr 10, 2011 5:07 am Post subject: Strange surging.

Here's the issue.
I've had various running issues with my 82 931.
Recently i took the advice of Grenadiers, (Thanks again) i adjusted the screw on the throttle body which thankfully got my car running again. I've put 150 almost trouble free miles on it in the last 2 weeks.
There are still some running issues. After about 30 miles the car will suddenly start to labour at idle, ill have to hold the throttle to keep the car running. Over 2000 rpm the car is amazing. I blew away a similar aged 911 Targa last week.

The most interesting issue i have is a full throttle surging feeling when going up hills. Between 2500-5000 rpm the car doesn't pull cleanly up hill. It feels like it's struggling to get enough fuel maybe. The car has always had this problem, even before the no starting problem surfaced.
Also there is a drop in power when taking hard left corners. Never to the right. I had a lot of fun on the twisties testing this. I replaced the two fuel pumps last year.
Also i was going to test the CSV again. The manual explains how to do this. I followed the instructions to the letter and basically i can't seem to fathom a decent answer. Is there a simple way to test this? Ill look through the how to's to see if it's in there.
I'm slowly getting my car back to how it was when i bought it. Everything seems to be so overly complicated and i'm not known for my patience.

Richard.
_________________
1982 Porsche 931 (Sold)
2000 Smart Fortwo (Waiting for import)
1972 Opel manta (Left in England)
1965 Chevrolet Corvair (Left in England)
2010 Mazda 3 (Ex got this in divorce)
1974 Triumph TR6 (sadly gone)
1968 Ford F250 Camper Special (Daily)

Harm · Joined: 02 Apr 2009 Posts: 1376 Location: Holland

bump

Being from the standard 924 frontier, I would like to mention that on a Non Aspirated 924 the ignition timing (distributor) might be a few degrees off, causing this surging.
This could also be happening to your Turbo?
Here is a 931 related example: http://www.924board.org/viewtopic.php?p=212749#212749

Regards, Harm.

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Not sure if the ignition on an 82 has adjustable timing.
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Harm · Joined: 02 Apr 2009 Posts: 1376 Location: Holland

Oh well, that's Toofah King Bad then…
Cheerio!
_________________
Porsche 924 NA 1982 LY7A/A3A3 _ Greater driving pleasure never harmed anyone.

Smoothie · Posted: Fri Apr 22, 2011 11:56 pm Post subject:

Ya, no timing adjustment on '81-up (S2). Though there is a wire running along the inside of the upper left fender (wing) that when disconnected, retards timing by approx 8 degrees (for use when high octane fuel is not available).
BUT (and that's a big but (but no pictures please)), it's possible that you have a vacuum leak that's actually a boost leak and opens up when the pipes are pressurized. I had this and found the lower pressure pipe (first one, and attached to the turbo compressor's outlet) was seperating from the turbo and opening up a large leak, but only under boost. At other times, including while searching for the problem at idle or with engine shut off, things settled back into place and the leak is not apparent.
Anyway, check that the lower pressure pipe is bolted to the front on the block. It should be held by a bracket with one bolt to the pipe and two bolts to the block. Normal failure sequence is the one bolt loosens. then vibration eventually causes the bracket to cut through the bolt, then the pipe is loose, etc.
Check by grabbing the upper pressure pipe from above, where it bends down toward the turbo and exert up-down pressure on it. It should feel firmly attached to the engine - too much movement seperate from the engine means the lower pipe is loose. -And/or get a look in there at the bracket itself.. A leak here can also be accompanied by a sort of exhaust leak sound, or air rushing sound.
Also check the other end of the upper pressure pipe where it attaches to the TB. That too should be bolted together and sealed internally with a large orangy-red o-ring.
Some have also found their wastegate control line torn/disconnected - this would be accompanied by a loud higher pitched air rushing/whistling sound.
_________________
"..it's made in Germany. You know the Germans always make good stuff."

'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

smart931 · Posted: Tue Apr 26, 2011 5:51 pm Post subject:

Thanks a lot for the input guys. I'll look into that Smoothie.
Been pre occupied recently as we are mid way through moving so i need to keep the car as mobile as possible. Was going to sell it before we moved but that's all on hold. The new place has a better work space (still no garage) so i can sort the problems out there.
I'll let you know how it goes as soon as i can concentrate on it again.
_________________
1982 Porsche 931 (Sold)
2000 Smart Fortwo (Waiting for import)
1972 Opel manta (Left in England)
1965 Chevrolet Corvair (Left in England)
2010 Mazda 3 (Ex got this in divorce)
1974 Triumph TR6 (sadly gone)
1968 Ford F250 Camper Special (Daily)

Nein37 · Joined: 29 Dec 2009 Posts: 513 Location: New London, CT

I thought of this recently with regards to your troubleshooting difficulties.

Make sure to unplug the OXY Sensor cable under the car. The connection is attached to the crossmember. This will force your frequency valve to a 50% duty cycle and rule it out as a possible source of trouble. May even solve your problems.

And FYI, besides better gas mileage the car can run happily without it ever plugged in.
_________________
1981 931 CGT replica, OEM CGT intercooler, .8 BAR WG spring, GTS Headlights, Innovative Wide band A/F, A/C delete, 16" Fuchs, Weltmeister 200lb lowering springs, Bilstein HDs front, Koni Sport rears.

smart931 · Posted: Fri Jun 24, 2011 12:05 pm Post subject:

Thanks for the advice guys.

I found a mechanic who has years of experience working on these cars, not too far from me. He's built some awesome racing Porsches in the past. Including the GTR!
Gonna drop the car in with him soon and get the whole car checked out. It'll cost me but i think it's worth it to really get the best out of a great car. I've still been driving the car, even though it's developed a "hiccup" over 3000 rpm. Seems to be fuel pressure related.
Can't wait to get to the root of the problem. Been too long since i had a proper blast in my car.
_________________
1982 Porsche 931 (Sold)
2000 Smart Fortwo (Waiting for import)
1972 Opel manta (Left in England)
1965 Chevrolet Corvair (Left in England)
2010 Mazda 3 (Ex got this in divorce)
1974 Triumph TR6 (sadly gone)
1968 Ford F250 Camper Special (Daily)

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

Are you still around? What is the status of your car?
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

smart931 · Posted: Mon Feb 20, 2012 12:20 pm Post subject:

Hey Rasta.
I sold the 931 to a nice couple on this forum.
I hope they're enjoying it, and they sorted the problems.
I was looking to replace it with a Triumph TR6, but i actually found a 68 Ford f250 instead. I know, i have a strange taste in vehicles. It's in excellent condition, zero rust and a really strong motor.

I do miss the porsche on twisty country roads. And the surge of the turbo.
_________________
1982 Porsche 931 (Sold)
2000 Smart Fortwo (Waiting for import)
1972 Opel manta (Left in England)
1965 Chevrolet Corvair (Left in England)
2010 Mazda 3 (Ex got this in divorce)
1974 Triumph TR6 (sadly gone)
1968 Ford F250 Camper Special (Daily)