I have had the CL for a couple of years and it has always been a little "surgy" at low RPM in 1st and 2nd. I assumed that this was normal. Recently I had my car in the shop for an alignment and when they drove it for a road test they said that I had a throttle body issue causing the surging.

Does anyone else have this issue with a 6MT?

 

Dirty/bad IAC valve would cause it. Carbon build up in the TB would as well. What's the mileage?

 

After switching to 4th gear yesterday I noticed the RPMs jump (3k to 3.5k) with no real speed gain for a split second. It happened a few times after that on other gears.

This was right after I installed the Icebox. This never happened before and I'm driving a 6-speed as well.

 

could be the dirty/clogged iacv. restart the car and it usually goes away (until you clean it, you gotta live with it)

clutch might be going

 

DRU2... this sounds like a clutch problem, but I am surprised that you would notice it in 4th without it also being evident in the low gears.

Fuzzy, mileage on the car is 180Km or 112K miles... what do you recommend I try?

 

Yeah that's a lot of mileage. Did you get the 100K service done? Timing belt changed?
1st I would clean the carbon out.

 

Major service was done at 100K and T belt changed as well. The mileage is all highway. I will look at the throttle body intake to see if it is dirty. I recently changed CAI and didn't see anything obvious. Should I remove the entire throttle body? Where is the IAC valve (and what does it do?)

Thanks for your help