'82 924 stuttering and jerking

PORSCHE KEV · 03-03-2008, 07:20 PM

I have a 1982 924. the other day it started stuttering and jerking in 2nd gear under quick acceleration,then it started doing the same under normal acceleration and now it pretty much does it in all gears. The only way I've found to control this is by accelerating ever so slowly and shifting
before 3000 rpm.I just replaced plugs wires cap and rotor. the car starts and idles great. In neutral while running I can rev the heck out of it and it sounds great (very responsive and very smooth acceleration) Any help would be greatly appreciated

924RACR · 03-04-2008, 09:04 AM

I'd wonder about clogging fuel filter or dying fuel pump...

PORSCHE KEV · 03-04-2008, 01:21 PM

there is a loud buzzing noise coming from the fuel tank area

924RACR · 03-04-2008, 01:37 PM

There should be, as that is the fuel pump... but there's a theory going that they make more noise before dying! How much is too much noise? Nobody knows, conclusively.

But your symptoms do sound to me like a fuel pressure issue. That said, it could be caused by a weak or overheating fuel pump relay as easily as the pump dying. Check the temp of the relay and fuse... carefully! I've burnt myself before on malfunctioning fuel pump fuses before. Turbos are particularly bad, in my experience, for burning fuel pump fuses - too many other circuits piggybacked off the one fuse - but yours being a late car could still suffer from the same fate.

Corroded contacts can also cause overheating components.

jmd_forest · 03-04-2008, 01:46 PM

You say you just replaced the cap and wires. Was that before or after this problem started?

jmd_forest

PORSCHE KEV · 03-04-2008, 03:59 PM

right before

bradelporsche · 03-04-2008, 08:55 PM

I had the same Problem!!!! first i thought it was the fuel pump then i thought it was the fuel pressure but i hooked up a fuel pressure gauge and it ready good pressure. and so i tracked the problem down to the fuse box apparently one of the pigtails in the back was badly burned and corroded so i replaced it and got rid of most of the jerking but it still does it under full acceleration, hmmm... 924RCR now that you mention it the fuse is getting VERY HOT I burned my self touching it! could a higher amp fuse be the fix for the jerking?

Tim Hancock · 03-05-2008, 05:43 AM

My '77 924 acted very similar when it's fuel pump started dying. Took me awhile to figure it out as at the time I did not have a pressure tester and it passed the timed free flow test in my repair manual.

malpaslane · 03-05-2008, 07:15 AM

Hi, if you find it is your pump, take alook at the pump inside your tank, i,ve had them stop working or need the filter on them cleaning and make the outside pump make more noize and work harder, so burn them selfs out. Rik

924RACR · 03-05-2008, 08:10 AM

Bradel - no, you need to fix or repair the wiring to reduce the current consumption. I ended up completely bypassing the pump fuse in my '82 931, installing two modern inline fuse holders to replace the single fuse which was overloaded. Schitty electrical design, the engineers who signed off on those changes should be taken out back and gassed in the proper German tradition

Kidding aside, I would definitely fix that problem, the fuses should not be running hot enough to burn!

Rik's right about the in-tank pump, very important point. However this does only apply to later cars and turbos; earlier NA's don't have the in-tank pump. Think the changeover might be around 80 or 81, not sure...

Dark Skies · 03-05-2008, 01:46 PM

Quote:

Originally Posted by PORSCHE KEV

right before

Have you checked that the cap is on correctly? They can be a bit fiddly - might show up under vibration - such as during acceleration.

onZedge · 03-08-2008, 03:35 PM

Quote:

Originally Posted by Dark Skies

Have you checked that the cap is on correctly? They can be a bit fiddly - might show up under vibration - such as during acceleration.

Loose rotor.

gtroth · 03-09-2008, 08:39 AM

Quote:

Originally Posted by PORSCHE KEV

there is a loud buzzing noise coming from the fuel tank area

Fuel pump can groan quite loudly when the fpr is bad (fuel pressure goes way high and pump can't work well against that). So you might go ahead and check your pressure. Not sure of any connection to your hesitation issue, but it's best to make sure things are right at a time like this...

bradelporsche · 03-15-2008, 10:25 PM

My car did the same thing and i found out why, a leaking headgasket. a few friends and i were driving on the highway and they said my car was throwing white smoke out of the exhaust. Just last weekend we did a high speed run 140 mph on the highway the car felt great even at that speed. well when we got off the highway everything was fine with the car but about 3 minutes later my car starts missing and a huge white cloud of smoke comes out the back. but at least i get to build my engine up, im making it a 2.2 2.3 liter with flat dished forged pistons and a 9.5.1 Compression ratio.