irocurpony8489

iTrader: (2)

i picked up my lt1 today it runs great but under high rpms it cracks and makes pop corn popping noise from under the hood and shakes around. car has 158,000 its a 94 z28. The car is throwing no codes is this a bad opti?

Blacklightning744

iTrader: (7)

sounds like a motor mount or a very worn out harmonic balancer

irocurpony8489

iTrader: (2)

its a miss you can look at the rear view mirror and black smoke will come out with is popping

Blacklightning744

iTrader: (7)

hmmm timing issue maybe, all your plugs /wires good?

Chevyguy358

iTrader: (4)

i would see if you can localize it to one bank...you may may a broken valvespring, pushrod or valve issue

irocurpony8489

iTrader: (2)

i let the guys at work drive it they seem to think its hitting the rev limiter because it hits 5,500rpms in first gear stays there then goes pop pop pop until u left of the gas wot. old owner said it has a shift kit i work at a trans shop they seem to think the 1-2 shift point is higher then the limiter? still doesnt explain why it runs badly at 4,500rpms

ORedRoc4

iTrader: (15)

Does the stutter get worse with heat? It may be a bad coil... try and get it checked at autozone.

-justin

irocurpony8489

iTrader: (2)

you can hold it to the floor in drive when your in first gear and it will not shift into 2nd at wot it stays at 5500 and pops likes its hitting a
rev limiter

Chevyguy358

iTrader: (4)

you need to have the PCM reprogramed

sweetbmxrider

iTrader: (13)

sounds like someone was effing around and didn't know what they were doing. could be a bad tune in the computer. can you manually shift it WOT?

irocurpony8489

iTrader: (2)

nope cant even manually shift it will start to run shitty starting at 4500rpms then it struggles and shakes to 5500 and just sits there and jerks and pops badly if i hold the pedal it just stays at that rpm and doesnt shift when i left of a puff of black smoke will come out the pipes. Other then wot this cars runs beautiful it looks like oil is leaking in my opti i wonder if this can cause this also i took my hand and beat the cat and you can here the catalyst broken up in the cat. popping sounds like its coming under the hood and out the exhaust goes away as soon as i let of the gas

sweetbmxrider

iTrader: (13)

a bad opti will definitely do this yes. broken up catalyst could be adding to the effect especially if its inhibiting the flow of exhaust

Geneticallybroke

iTrader: (3)

start with a tune up maybe it still has the factory plugs

Blacklightning744

iTrader: (7)

now that you say that i'd double check to make sure its a bad cat, if it is then replace it asap, if you dont the cells might fuse together and the exhaust gets so back up it blows up your engine.