Exhaust system loose?

 

Good idea. I’ll check into that.

 

Hi @buildadog ; !

What is your idle rpm when in gear, under the conditions where you get the vibration? On the face of it, it sounds like your idle might be low for some reason. When you turn on the AC, the computer will run the idle higher to compensate for the additional draw on the engine.

 

Good question. Without he AC on, the idle is about 600. With AC on it fluctuates every 5-10 secs or so between about 600 and 1100 I’m guessing to run the compressor.

 

Have you identified and solved the problem yet? Dr. Dyno suggests that the exhaust system might be loose - could be a heat shield as others have complained about the noise which you have and the noise has sometimes been reported as being caused by a loose heat shield.

 

I think I’ve solved the issue. Cleaned MAS and throttle body and idle is now ~1000 rpm in gear. No vibration at all. Idles much more smoothly when AC is on. It used to jump between 600 and 1000 when compressor kicks in. Now it’s pretty much stable at 1100 rpm with AC on.

 

Just a thought. Do you have a small vacuum leak in the system somewhere - I think on MAF engines, low idle could cause a rough idle.

Are you able to look at any scan data at all to look in to fuel trims at idle a d say at 3500 rpm? I say this because on one of our cars, I had a dirty MAF (low readings from scan data) and a vacuum leak (high fuel trims at idle and normal at 3500rpm). Sorted these out and idle was back to normal.

Just some thoughts

 

glad it looks like it is sorted