924Board.org

[ih007]

Thats the only way i can think of to describe it anyway!

Under load ie acceleration, you can 'feel' the engine stuttering/hammering. I've replaced the plugleads as the resistance on a few was out but its not really helped much. Do i need to look towards ignition or fuel?

Could replace Rotor arm, plugs etc but thought i'd try for some advice first. All help gratefully digested!
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If it ain't broke, dismantle it anyway. It soon will be!

[Chrenan]

Is your air sensor plate moving freely? Maybe it is sticking and restricting the fuel getting to the cylinders under acceleration and load when the plate should be fully open?

How is the timing on your car? Could the timing belt have slipped a notch (from a loose tensioner maybe)? Is the distributor bracket tight? If not, the distributor may have moved which also knocked off your timing?

Is the car only rough under under load? Is it smooth at idle? How are you motor mounts?
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1987 951 - M193 Version for Japan

[ih007]

I havent checked the air sensor plate, so thats something to look at. As far i know, the timing is spot on (was checked a month or so back).

The idle isnt perfect, but not bad. I'm not sure how the engine mounts are, but from how it feels, its almost certainly more than that. Its a definite stuttering that wouldnt be caused by the mounts.
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If it ain't broke, dismantle it anyway. It soon will be!

[1982Porsche924]

Sounds like a fuel related issue to me. I would check to make sure your a/f mixture is fairly close to where it should be at idle (Turn the 3mm mixture adjustment screw at the fuel distributor to the left 1/8 turn at a time until the motor pops under deceleration, then give it 1/4 turn to the right). If the mixture is correct, then I suspect your Warm Up Regulator is bad.

Also, get a can of carb cleaner and spray around vacuum lines. If the idle changes when you spray somewhere - you have a vacuum leak. This could also cause the problem.

Good luck!
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1979 Porsche 924 "S"
Engine: Euro pistons, Light Flywheel, Weber TB, Bursch Header, Cam Wheel
Suspension: Front coil-overs, adj sways, Solid bush. Thicker tors. bars, 5-bolt, BBS rims
Body: Fiberglass widebody kit, 931 Nose

[wdb]

you should also check your spark and injectors .if any cylinders are not firing it can act like that . with the engine running pull and replace the spark plug wiires one at a time . if any cylinders are barely firing or not at all there will be no difference in the idle ,when you pull that wire , when you pull the wire of a cylinder thats firing well ,there will be a noticable diference in the idle . also check to make sure the plug wire are right on the distributor , if they are in the wrong order , it can also do that .

[ih007]

I'll try a few of these suggestions then and post again on monday to let you know the results.
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If it ain't broke, dismantle it anyway. It soon will be!

[ih007]

A few days early but i've checked it out. Pulling out each lead in turn showed no change on cylinder 3. Sure enough the plug was fouled and looked a little unhealthy. So, 1 new plug, problem solved. Now i wait to see if it happens again to see if the plug was duff and got fouled up through not firing, or if oil gets past the rings/valves and fouls the plug causing no spark. Of course a compression test would help no doubt, but time will tell.

Thanks for the help guys.
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If it ain't broke, dismantle it anyway. It soon will be!