924Board.org

[januarytiger]

I really need help,
i recently purchase a 1982 924 5 speed manual.
after 6 mnts of being driven daily, i now have a very violent jerking when i hit 2500 rpms, not 2000 not 3000, im thinking clutch, or fuel related. but i cant tell. it feels like the engine drops in power the comes back and i make the drive shaft go..."ka-chunk ka-chunk ka-chunk, the whole car jerks forward and back.
i admit the car was in bad shape when i purchased it, i have replace the fuel pump in the gas tank, (it was leaking)
should i look at clutch?, driveshaft?, fuel system?, engine?,
it only happens at 2500rmps, it has increased in frequecy!
john

[Lizard]

I would start with the fuel system.
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3 928s,

[endwrench]

Definetly a tuning problem of some sort. I think due to the odd layout of these cars drivetrain and the small diameter shaft used to couple the engine to the trans you can get this cyclic bounce and jerk thing going. I expereinced it quite a bit in my car while tuning my EFI system. If you do not have smooth transitions between loads ranges things can get pretty violent. I don't know too much about the '82's but I think they have a lambda feedback system that could give you fits. I would try unplugging the O2 sensor and see if this helps. It could be getting old and slow and giving you a cyclic problem. You might try unplugging the EGR and see what happens also. If these leak or get weak it could give you fits too.

Todd

[januarytiger]

thanks for the direction
im looking to purchase a o2 sensor.
in the larger scheme of things i plan to replace most parts.
ill keep posting updates

i have a option code question and didnt know if i should post here
(my 82 originally had the factory alarm)

[numbbers]

You didn't mention if it was under full throttle or not. If it is happening under full throttle accelleration, then, my guess is the wastegate is not working properly, and you are getting enough boost to activate the overboost protection switch which cuts power to the fuel pump. It kinda feels like someone slamed the brakes on.
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1980 924 Turbo

[Lizard]

I dont think he has a 931 numbbers, indicating that he wouldnt have a overboost switch.
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3 928s,

[pyromjm]

No EGR on the '82.
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1982 924 NA gray/silver with black int.

[januarytiger]

had time to get under 924 and disconnect oxygen sensor today.
unfortunately i still have the drive train jerk at 2500 rpm's,
some good news, it is less violent, but still there,

i do not have turbo.

being under front i did notice some oil on clutch bellhousing, hope
none is on flywheel.

the jerking comes on when gas pedel is lightly press
no jerk if full throttle or idle.

[gohim]

I would guess that you have the mixture and idle speed set wrong.

The 81 and 82 use the same ignition and fuel system setup (which is different from earlier model years, and more sensitive to adjustments).

The problem usually starts when a vacuum leaks occurs (the fabric covered small diameter vacuum hoses crack and leak). This brings the engine into a lean runnig condition, and the ide speed falls. Then, somebody that doesn't know what he/she is doing, simply cranks the idle speed adjustment on the throttle body to bring the speed up. That makes the engine run even leaner. At this point, someone tries to correct the problem by cranking up the idle mixture screw, which further messes up the adjustments.

At some point, the O2 sensor system can no longer correct the mixture, and the idle speed will start hunting. Before this happens you will notice a flat spot, off idle, when you first come off the throttle stop where the engine bogs, before depressing the pedal further to get past the problem.

99.9% of the mechanics that I have come across do not know that you need to disable the electronic idle stabilization system, and warm the engine up to operating temperature, BEFORE trying to adjust the ignition timing, idle speed or idle mixture on a late model (81 and later) 924.

[januarytiger]

i had time on sunday to give the engine bay a good look over
for any cracked, dislodged or leaking vacuum hoses.

the previous owner replaced most vacuum hoses with heater hose.
this is a good thing
the tiny vacuum hoses are still the original ones, but look okay.

then by pure luck i located a completely missing hose, it is hard to
see since it is way back next to the distributor, under the air intake
distributor, almost to the firewall.

only thing left is the clamp and bits and pieces of hose,
from what i can tell its been missing for a long time now.

no reference or picture in the haynes manual

can anyone tell me what this is and where does it connect too?

[gohim]

The small vacuum hoses are the ones that crack and leak.

If they are really original ones, they are probably leaking.

You can't really tell how they are by looking at them. Try folding them back in 1/2. If they crackle, or are stiff, they need replacement.

To figure out what the unattached hose is, you need to present more information.

[januarytiger]

sorry for all the excitement abou the missing hose.
i did find what it is, its the Engine Breather, as detailed right
here on 924.org in the tech section under engine

i guess i have to purchase the hose from my porsche dealer
so i can guess at what it is attached to. the article on this site states
that depending on year of veh, there are different configurations

any one have any shop manuals that outline the 1982 layout?

this may or may not help the jerking the engine does when the
pedal is slightly depressed.

[bryanc]

jantiger,
Is it red?
Did you get from me?
I won't abandon you!
EMAIL me back and I will try to help.
My email is in my profile.

Good luck,
BC
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'84 944
I'd rather have a bottle in front a' me than a frontal lobotomy
Tom Waits