x Wild Bill x

Alright guys, I have a 95 Firebird Formula with 116K and the 4L60e. The car shakes at a certain RPM, from like 1000 up to 1600 and after that the shake goes away. I cannot figure it out, the motor mounts are good and I just changed the transmission/converter and it shook before and after so I know it's not those two. I made sure the torque converter bolts were all the same and the flywheel looked good. I am going to go check the harmonic balancer right now. After that I have no idea what to do, I was thinking check 02 sensors and then the ICM. It has new plugs wires and opti spark that were put on before I bought it and there are no sparks jumping at night. When it shakes it vibrates the whole car and seems to get a little better once the car is warmed up. It feels like it has good power but does take a little while to fire, that's why I'm thinking ICM...

Thanks a lot,
Bill

ss.slp.ls1

iTrader: (36)

How did you verify that the motor mounts are good?
Check the trans mount & TA mount.
Could be an unbalanced driveshaft.

x Wild Bill x

I took a big pry bar and lifted up on both sides of the motor and neither side moved easily. The trans mount as well as TA mount are good as I just inspected them when I put in the new transmission and I don't think the DS has anything to do with it as the car will vibrate in neutral... So I feel it is not drive train related, I just swapped the ICM from my 94 Z28 and no difference so we can rule that one out, I haven't been able to check the balancer yet, but does those go bad often? What do they look like, the rubber looks a little weird...

Thanks,
Bill

creepingdeath94

iTrader: (1)

Maybe a misfire...stumbling/vibration from that perhaps. I had leaking valve seals on my '94 years back on number "8" and it would vibrate/buck around that rpm range as well. Pull the plugs and inspect them maybe. See what kind of story they tell. Should help you figure out if it is running rich/incomplete combustion/running lean/etc.

x Wild Bill x

Yeah, I was thinking to check the plugs after I check the balancer, but unfortunately it is going to rain here all day so I won't be able to work on the car for a day or two. I will let you guys know what I find so we can try to figure this out.

Thanks,
Bill

C5042081

iTrader: (5)

hmm i have just about the same thing, shakes at certain rpms not driving, anxious to see what you find

C5042081

iTrader: (5)

well i just found out my prob my trans fluid was low, put a quart back in and it stopped the shaking, hope ur is as easy as mine gl