Idle stumble every 5 sec.?
 

Driving the old 944 around and a new bug appeared. I had been driving around about half an hour - air temp aprox. 60F - Pull to stop light - idle drops to 800-900 for one sec. then goes to normal 1000-1100 then does it again. I notice it seems to be at regular intervals - I count it out and it is about every five seconds.

The car accelerates fine and otherwise seems to run well.

Any ideas?

I am taking the car in to a mechanic for a t-belt job March/April so I would like to get as many little fixes in before that. You know how it is when you take a car to the shop "oh buddy your gonna need a whole new framis system!"

TIA

unplug your lambda and see if it still does it.

Is that the O2 sensor?

Yep, O2 sensor

If it is running fine otherwise, I am more inclinded to believe O2. If it were running rougher, I would think vacuum leak.

Sorry, vague, I know, but this is one of those "could be one of 4 different things" problems

AFJuvat