Z20ATE

i have a 94 z with the basic bolt ons that has a very annoying studder when i'm cruising. it only happens when im barley touching the throttle. its almost like a miss but very random. about a year ago i installed a 58mm tb then shortly after that I installed a custom grind cam from comp (233/238 531/541 110 LSA). i noticed the studdering after the cam was installed. about a month later the opti crapped out so i replaced the insides and the problem still excites. since then ive also replaced the coil, icm, and plugs. the only thing i havnt replaced yet is the wires, they are 8mm taylors and they have been on the car since i bought it so im not sure how old they are. the last thing i noticed was when i swaped plugs from tr6's to tr55's the studdering was less noticable but def still there. if anyone has any idea what it could be id appreciate any help thanks.

lt1z28camaro

iTrader: (2)

cam surge? Mine will do it at 1500rpm..

integraxtc

iTrader: (11)

What's cam surge?

Z20ATE

I thought tat might have been the case but i didnt think the cam was big enough to cause that

djjab57

iTrader: (17)

mine is doing the same thing. it is almost gone since i took off my aftermarket coil and put the stock one back on but still has a little. only happens when slightly pushing the pedal and i have stock cam

ss.slp.ls1

iTrader: (36)

I think it's big enough to cause slight cam surge under light throttle at very low rpms. Does your TB ever get sticky?
You could always go from zero throttle to WOT every time to avoid the symptom. JK.

Z20ATE

no the tb has never gotten stuck. and believe me i have gone wide open a few times when its doing it because it drives me nuts

pointvirus

If it only does it with light throttle and not WOT, try checking the O2's. Worked for me, it would feel like the car was getting stuck, and all the sudden it would surge forward.

tylert14

iTrader: (11)

The stock PCM makes the AFR leaner at cruise to save gas and for emissions. The bigger cam is letting unburnt gas leave the combustion chamber and the O2s read this as it running rich at cruising RPMs so it leans out the tune way past lean (it overcompensates). Won't hurt anything while cruising but it produces that annoying shudder you feel.

I see it get mixed up with cam surge all the time. Old (not necessarily bad) O2 sensors can worsen the condition. Just swapping to a new set of AC Delco O2s might solve it. If they don't it's a tuning issue that needs addressed.

Hope I helped, I've had this issue a few times. Short term fix, you can unplug one of the O2s and the shuddering will go away but it won't run as good. It won't be using the O2s to adjust AFR.

Z20ATE

the above makes sence. once i get some money ill have to give it a try and see what happens. thanks for the info