Rough Running '86 3.2

[spg356]

Greetings,

I have a rough running '86 911. It is a 30,000 mile original car, 2nd owner. Was running fine and then all of a sudden it seems to be running on 4 or 5 cylinders. I do not believe it is the gasoline as it started to run this way at half a tank from a fill up from the same gas station I've always used.

No backfires, spitting or pops; just runs rough as. I could start with puling plugs to see which cylinder is the culprit, but I would like some more ideas before I start to work on it.

I have lots of general suspicians but would like to know what you would do in this situation. Does anyone have a good progression of what to check and in what order?

Thanks!

[wvicary]

I would pull the spark plugs as a first step. Keep them in order according to cylinder location and they will tell you a lot about basic engine health.

[spg356]

Thanks, that is a great first step. I am also looking for what to do after that. In other words, a kind of a flow chart of what to try and in what order if you were to have the same problem.

Regards,

Edited July 10, 2012 by spg356

[Richard Hamilton]

Check plug leads, distributor cap and rotor arm too.

[wvicary]

Compression test when plugs removed and leak down test if you have the equipment.

Do you know the maintenance history of the vehicle?

[spg356]

Do you know the maintenance history of the vehicle?

Yes, dealer serviced the entire 30k miles.

Thanks again for the replies, any other things to check are quite welcome!

[wvicary]

Even though the dealer did the service, check the invoice to see what they actually replaced.

[intubator]

cylinder head temp sensor.

[EleCTriCT]

all the above mentioned... when they say check the leads, a quick one is to just make sure they are all seated properly... they tend to vibrate loose when they get old and sloppy and kind of just sit on top of the spark plug.

since removing the wire is the first step to getting at the plug you need to make sure one isnt loose before you take it all apart and possibly not find anything wrong (look deep inside the lead with a light if you see green corrosion replace them)

[sithot]

DME uses a sensor on the flywheel. They do go bad (or at least the trigger can). Change the fuel filter if it hasn't been done already. Does sound like ignition though.