944 Runs Rough

[aviscomi]

I posted an item a few days ago about how my 1986 944 ran rough while it was damp outside. Well its been dry for about 2 days and no change in the way it idles or runs. While idling, I pulled the first two fuel injector contacts of (both at the same time) and I noticed no change in the idle.

Could I be getting close to the source of the problem?

TONY

[carsonmx114]

yes your are close in that you know which cylinders are down. your engine needs three things to run, compression, spark, and fuel. if no. 1 or 2 are missing compression or spark then taking away the fuel won't make any difference. try pulling the spark plugs out and looking at them, if they are dark and wet then you are probably missing spark or worse, compression. if they are white and chalkly you are missing fuel. your dme control unit has two fuel injector output wires so the injectors do work in pairs, they all share a ground but i can't remember which ones are paired together. they make a noid light which is a low amperage test light to test injector output voltage. if you could get access to a noid light, a spark tester and a compression gauge you could find your proplem in no time at all. let me know what you find out.

[aviscomi]

I pulled the plug, actually I replaced them, and they were dark & wet. The strange thing about this problem is that the engine ran fine the day before it rained. I wen to start the car the following day (the rainy day) and it ran terrible and still is.

[carsonmx114]

i was thinking about your car this morning and realized some of what i told you was wrong. the injectors share 12v not ground. the ground comes in the form of a pulse from the dme unit but if your plugs were wet i would guess the injectors are working. i would plug in a spark plug you know is good and rest it on the cam cover turn the engine over and look for a spark. i think your problem is in the ignition. i'm leaving for work now, let me know if your getting spark to the new plugs. good luck!

[aviscomi]

I replaced all 4 plugs & wires...still no change. I just order a cap & rotor online. If this doesn't work I may have to take the car to a tech.

[carsonmx114]

i still think you have a ignition problem. you might double check your firing order i know the car was running good but i wondered if maybe you had a moisture problem in the cap to start with and after you removed the cap maybe had the firing order reversed on 1 and 2. also you might check the cam timing, i don't know if that could cause your problem or not. you may know but remove the black rubber plug next to the distributor, turn the motor until you see the timing mark on the cam gear, no.1 piston should be at top dead center. there is a window at the top of the bell housing, it's hard to see but you should see a mark on the flywheel. hope you figure it out.

[carsonmx114]

hey me again! i just woke up with another idea about your car. about a year ago my throtle position switch went bad. the car would barly run, i just barly made it home and i got worse to the point that the car would not idle at all. i found the problem by unpluging the tps and starting the car. this puts the engine into closed loop mode, if this is your problem it won't run real well but it should run alot better with the tps unpluged. with the engine off when you open the throtle from under the hood you should hear a click from the tps, when my switch was bad it didn't make the clicking sound at all. hope this helps.

[aviscomi]

TPS...is what? Throttle Sensor? Where is it located?

[aviscomi]

Problem solved! I'm night quite sure how I solved it though. I began by starting to remove the Throttle Body, I got no further than removing the Air Intake hose(s) and look into the Throttle Body and noticed a lot of build-up. I sprayed it down with Gumout, wiped it out and put it back together. The car idled & ran fine! Just at that same time the UPS man showed up with my new Cap & Rotor. There still seems to be a slight miss, but its bearable.

These forums are great for a Porcshe novice like myself; my project last year was a 1988 Jeep Wrangler and their forums were a great help also.

Thanks for all your help!
TONY

[carsonmx114]

that's great that your car is running better. i meant the say throttle position sensor not switch. it's on the side of the throttle body with four or five wires coming out of it i can't remember for sure. you may have moved something around inside the sensor that made it start working so keep that part in the back of your mind if it starts acting up again. i'm glad your situation is improving!