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bill188 · Joined: 23 Jun 2006 Posts: 6 Location: Clinton, TN

'80 931. Has been running great for the last several months. Have done lots to the motor, new fuel dizzy, turbo, injectors, etc. But two days ago it started to lug (miss) just at 3000 RPMs. Above and below run fine. Today I took it out and above 2500 RPM's it now lugs real bad. By that I mean the engine will run then quit for about a 1/2 a second then run. It is an erratic spasm which happens about 4 or 5 times a minute. Idle is good. I can rev it up without a sputter. Just seams to be a problem under load. Any ideas.

Thanks;

Bill
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1980 931 bought in 2005
Bought a 924 in July of 1976 - kept it 11 years

Paul · Posted: Fri Mar 28, 2008 8:24 am Post subject:

Start by checking every hose and hose connection from the air cleaner to the throttle body for leaks.
_________________
White 87 924S "Ghost"
Silver 98 986 3.6l 320 HP "Frank N Stein"
White 01 986 "Christine"
Polar Silver 02 996TT. "Turbo"
Owned and repaired 924s since 1977
Porsche: It's not driving, it's therapy.

Smoothie · Posted: Fri Mar 28, 2008 10:16 am Post subject:

What Paul ^ said.
+ sounds like it could be part of the intake plumbing's getting pushed apart when under boost. This is a known problem that occurs when the small bracket that holds the lower section of the charge tube to the block becomes loose - and that happens due to one of the bolts loosening, then either working itself all the way out or vibrations eventually cutting through the bolt. -Then when boost comes on, the pressure pushes that lower joint apart, causing hesitation as air escapes from between the turbo and lower charge tube, boosted air pressure is lost and the A:F mix gets itself screwed-up.

Another possibility is torn wastegate diaphragm. Symptoms of that are a plastered back in your seat feeling followed by a sudden severe hesitation that feels like the car's trying to throw you through the windshield. This happens with a torn wg diaphragm because at first you have unlimited boost, then the overboost cutoff switch opens up and cuts power to the fuel pumps.

-But neither of these account for the preceeding symptom of a problem only at 3k rpm...
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"..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

bill188 · Joined: 23 Jun 2006 Posts: 6 Location: Clinton, TN

Well My bad. I posted before opening the hood which I did this PM. First thing I touched was the dist. and found the cap was loose. Snap it back on and It ran like it should.

Thanks all
_________________
1980 931 bought in 2005
Bought a 924 in July of 1976 - kept it 11 years

Smoothie · Posted: Fri Mar 28, 2008 11:58 am Post subject:

That's another known problem - if the distributor mount isn't installed right.. It leaves the distributor angled up too high, the cap and wires hit the hood, and the cap gets knocked sideways.
_________________
"..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