Running Badly Please Help

[jaubuchon]

87 911 3.2 cabrio widebody, autothority maf, no cat.
My car is horribly running, rough, low on power from 2k to 3k then 35 to 4k but then it clears, done a cap, rotor, 02 sensor, all fuel system gone over, alarm removed, tank cleaned, plugs, alternator checked out, not sure where to go now.
Please help

[boss11]

ignition leads?

[jaubuchon]

Originally Posted by boss11

ignition leads?

all ohm ed within range

[ischmitz]

Does it have the stock barn-door AFM or an aftermarket conversion with hot-film sensor and modified DME? I assume it's the later when you say Autothority. I believe the kit is a modified chip (accounts for the different response function of MAF), a hack in the DME (power to the MAF) and the MAF itself.

Then your Garage says it has an electric Turbo?! - can you elaborate

What changed or was it always running terrible like this?
Was the change gradual or sudden?
Do you have the stock parts and can you put them back? (you need a stock DME & AFM)

If not my first guess would be something on the conversion went bad and you are stuck with replacing it on a hunch. The filament in these sensors can become contaminated with time giving wrong readings. Depending on the model used some have a self-cleaning function (heat up wire real high on start to evaporate contaminants) but others don't.

Not a good position to be in....

Next the usual suspect that affects mixture: vacuum leaks.

Ingo

[jaubuchon]

Originally Posted by ischmitz

Does it have the stock barn-door AFM or an aftermarket conversion with hot-film sensor and modified DME? I assume it's the later when you say Autothority. I believe the kit is a modified chip (accounts for the different response function of MAF), a hack in the DME (power to the MAF) and the MAF itself.

Then your Garage says it has an electric Turbo?! - can you elaborate

What changed or was it always running terrible like this?
Was the change gradual or sudden?
Do you have the stock parts and can you put them back? (you need a stock DME & AFM)

If not my first guess would be something on the conversion went bad and you are stuck with replacing it on a hunch. The filament in these sensors can become contaminated with time giving wrong readings. Depending on the model used some have a self-cleaning function (heat up wire real high on start to evaporate contaminants) but others don't.

Not a good position to be in....

Next the usual suspect that affects mixture: vacuum leaks.

Ingo

Maf, runs bad with or without turbo, just started running bad one day, dont have stock parts bought already converted, done vacuum checks

[jaubuchon]

So does anybody have any more ideas as to what it could be, i'm getting to the point where i'll take it to the crooks in town at the porsche shop

[snbush67]

Double check you plug wires and firing order.

[jaubuchon]

Originally Posted by snbush67

Double check you plug wires and firing order.

did already unfortunately

[DCinVA]

Check the idle microswitch. Its located on the throttle body, and it tells the DME that the throttle is closed. Sometimes when they go bad, they get stuck in throttle closed mode, effectively telling the DME the throttle is closed, even though you are pushing on the pedal. I believe the WOT switch overrides the idle switch. How does it run under Wide Open Throttle?

The classic symptoms of a bad idle microswitch are.
Engine idles fine.
Engine runs fine at Wide Open Throttle.
Any other throttle position results in bucking, running rough.

[jaubuchon]

Originally Posted by DCinVA

Check the idle microswitch. Its located on the throttle body, and it tells the DME that the throttle is closed. Sometimes when they go bad, they get stuck in throttle closed mode, effectively telling the DME the throttle is closed, even though you are pushing on the pedal. I believe the WOT switch overrides the idle switch. How does it run under Wide Open Throttle?

The classic symptoms of a bad idle microswitch are.
Engine idles fine.
Engine runs fine at Wide Open Throttle.

Any other throttle position results in bucking, running rough.

Thank you I will try that

[Nuen Werke]

coil?

[DCinVA]

Here is a simple test for the secondary wiring (plug and coil wires).
Wait till dark.
Turn off all the lights.
Open engine lid.
Fire up engine.
Visually inspect for small lightning bolts.
If you see any sparks at all, replace the secondary wires.