93 z28 hesitation at 4k rpm

[93z]

My brother has a 93z28 6 speed with CAI and exhaust. His car runs fine up till 4 grand and then it seems to hesitate and stop pulling. Almost like it has a miss. Usually, once it passes 4-4500 it runs fine again and pulls hard up to the red line. Any ideas as to what could cause this? THX

[KissMyWhtSS]

Does it occur under WOT, partial throttle or both?

For starters I'd hook up a Fuel Pressure gauge and run it out over the hood and drive it a bit and see what your fuel pressure is doing. I'd also suggest checking the plugs and probably replace the fuel filter if you've never done it.

[My95Z]

Does it occur under WOT, partial throttle or both?

For starters I'd hook up a Fuel Pressure gauge and run it out over the hood and drive it a bit and see what your fuel pressure is doing. I'd also suggest checking the plugs and probably replace the fuel filter if you've never done it.

X2, I'd also have the coil pulled and checked.

[93z]

It does it under WOT and partial throttle, and does it nowhere else in the rpm range

[crows93z]

sounds like the same symptoms i'm having. after replacing like 5 different sensors, coil, plugs/wires, everyone is telling me it's a failing opti, which i guess is acceptable since mine has 160,000 miles on it.

[BIGT94z]

the opti is on its last leg. my old camaro did the same thing for about 1k miles then the opti finally went out

[93z]

It was a spark plug wire that came off of cylinder 7
thanks for the help

[KissMyWhtSS]

It was a spark plug wire that came off of cylinder 7
thanks for the help

hehe I guess I should've mentioned checking the plugs/wires, glad it was a simple fix.