TrackJunke

I have been having an issue with a vibration at idle in my car. I installed RS motor mounts about a month ago. I only seemed to really notice it recently but that does not mean it has not been there since the install. My idle is solid right below the 3rd mark up on the tach (800 RPM). If I turn the AC on the vibration goes away. The idle goes up to a little bit above the 3rd mark with the AC on. The vibration feels like it fluctuates (up and down surge) a little if you know what I mean. The bolts to the motor mounts are tight. Today I cleaned out the ISV but to no avail. I am still having the problem. The distributor cap, rotor, and spark plugs have all been changed recently (30k service). I am kind of stumped. Any ideas? Thanks.

Steve Weiner-Rennsport Systems

Hi:

Couple things:

1) How old are your oxysensors?

2) Did you check for any vacuum leaks? There are many places for potential false air leaks that cause idle flucuations from an incorrect mixture.

TrackJunke

I dont know how old the O2 sensors are, I only got the car a few month ago and put about 3k miles on it. About 30k miles on it right now. I did not see any record of replaced O2 sensors. Where should I check for vac leaks? Will this cause any damage to the car?

dale_loch

To check for Vacuum leaks you can get a can of starting fluid and spray little bursts around your injector stacks, vacuum lines etc. If you see a surge in R.P.M.s while it is idling, you have discovered your vacuum leak.

Steve Weiner-Rennsport Systems

Don't ever use starting fluid,.............! First, its mostly ether and very dangerous, further,...ether does a VERY good job of washing oil off those expensive cylinder walls.

Use carb cleaner and follow Dale's instructions.

You'll need to plug one of the Porsche scan tools or a generic OBD-II tool in to measure oxysensor voltages and watch them cycle. That's the way you see if they are functioning correctly.

dale_loch

Thanks for the correction Steve, I didn't realize what I had posted!

Ooops