SLIGHT MISFIRE

[Guest]

HI THERE,ITS A1982 3.0 911SC 204 BHP MODEL.THE CAR RUNS FINE WHEN YOU GET TO 2500 RPM AND BEYOND. ITS ONLY A SLIGHT MISS,NO SMOKE,NO NOISES GOES LIKE STINK WHEN YOU BOOT IT.HARDLEY NOYICE ITT REALLY BUT ITS THERE IF YOU KNOW WHAT I MEAN.CHEERS.JOHN

 

[Guest]

Had the same thing on mine and Tuthills changed the leads - now spot on.

 

[bones]

Give us some more details, how often do you drive it has it been standing for long over winter, etc? Before you buy new plug leads a check you can perform to observe arcing to ground is to run the engine at night with the engine lid up and spray a fine water mist (from a plant sprayer) around the plug wires and attached components. Even if you don't see arcing you still may have a lead problem as the Beru plug caps have resistors inside which break down under heat (bad design idea). Clean the terminals of the coil, unplug the green wire that goes from the dizzy into the engine bay wiring harness and clean and spray with an electrical contact spray. Remove your dizzy cap and check the inside for damp, wear and burning. If you see anything suspicious there replace the cap and rotor (read the numbers on the rotor before ordering to make sure you get the corect one).

 

[SJW BASIRE]

I had a faulty spark plug on my car.It was causing the plug lead to arc onto the heater hose on the left side of the engine.It was a genuine plug from a Porsche service kit aswell.[]

 

[Guest]

Had the same on my SC to check the leads/plugs I let the car run at tick over when warm and pulled each lead off one at a time soon found out that it was number six, so checked the plug for fouling/operation etc this was okay, so since the leads looked very old and some of the rubbers on the plug caps where broken I bought a new set of leads. Very expensive as they have to be shielded on the SC. I eventually found a set of Beru leads for 90 quid at GFS (www.gsfcarparts.com) this cured the problem and also I noticed better cold morning starting.

Rats

 

[sep4]

Some years ago my 2.7S would miss on a light throttle when warmed up, and accelerating gently away from a roundabout, or in traffic. This was a fault in the ht leads. I stripped out old leads and replaced with best quality copper-cored ht cable cutting each new lead to the identical length of the old lead, and carefully threading back through the braided covers. All connectors were fine and ran with these for many years. The genuine cable sets probably cost more then than they do now. Dirty job to do, however.
You've probably ordered your new set by now.
Let us know your results.
Cost to me for the ht cable was at most £10.

 

[bruceb]

My car also had a slight misfire at light throttle loads and low speeds. I also replaced the leads and this helped but did not cure totally.

I then removed the fuel injectors and had my local Bosch agent flush thru. He explained that the injectors need to spray fuel in a cone shape into the inlet manifold. At low speeds and part throttle when the injector need only supply a minimum amount of fuel, with dirty or gummed injectors the fuel cone spary is lost and fuel just dribbles out in drops and hence atomisation is lost leading to misfires.

For £30 for all six injectors plus £12 for new o-ring seals this was bargain and resolved my misfire.

Bruceb