I have been dealing with a partial throttle engine shudder for a little while now. It is most noticeable while I'm staying in a certain gear for awhile but not accelerating really quickly. Sometimes it's really noticeable(even other people in the car comment on it), and sometimes I can't even tell. I used to be throwing an occasional egr fault code(32 maybe?) but I fixed a vacuum leak in my engine and haven't had the code since.

I have taken off my egr valve and cleaned it, but when I took it off initially I didn't really notice any buildup on it or the intake manifold, even my egr gasket was still in perfect shape. I did notice that when I took off my valve it took both thumbs to push the diaphragm down, but I don't know what's supposed to be normal.

Also, I am running quite rich in the upper rpm's I think. I can tell because of carbon deposits that form on my chrome tips only at extended rpms(not to mention the fuel smell). I think I have original O2's.

I have Replaced:
Plugs
Wires (15k on them)
Opti (15k on it)
Cleaned Maf and TB/IAC

Sorry for the book. Thank you for all the help in advance.
-Brad

 

Lemme guess, you keep your foot at a constant pressure, and it gradually gets worse untill it either corrects itself or you apply more/less pressure to the pedal? Sometime it'll even do it at idle?

If you answered yes to the preceding questions, go to GM Parts Direct and cut and paste this part # in: 25312184 to claim your prize.