Studdering under light throttle
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From: maryland
Studdering under light throttle 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.
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
You could always go from zero throttle to WOT every time to avoid the symptom.
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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.
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.
