I have a 1988 IROC with a 305 TPI and 5 speed, it has a 3.08 posi rear. The chip in the computer is a Hypertech and the clutch is a center force. It has Edelbrock headers and a Hooker muffler.

Ok this car runs great it starts everytime and goes where I steer it and brings me back home. When I run the engine up to 3500 rpm I feel a vibration but it dosent seem to be from the wheels(Original Iroc wheels) as far as balance is concerned the tires are older. It feels like its in the engine. And then it goes away about 3800 rpm. The plugs are new and cap and rotor are very good shape. Not sure how old the wires are.

The drive shaft has been rebuilt new u joints and balance.

It also seems to whine at speed.

My plugs have less than 200 miles on them and they seem a little dark with a little fuel smell.

Could this be something with the ignition? The Hypertech chip? A broken motor or trans mount?

Thanks the help

Mike

 

Any ideas, good ones or off the wall long shots?

 

does it do it in every gear or just in first gear? I would guess that if it does it at the same rpm level in multiple gears it would probably be engine related where as most vibrations coming from tires,wheelbearings or front-end vibrations etc.. are noticed at a certain speed and not engine rpm. Does it do it with light and hard acceleration?

 

It does it in every gear, under light or hard accealeration. The only difference I have noticed is that at highway speed it seems not be as much when your in fourth gear when you run it up to 3500. I dont remember if fifth gear does it.

Dosent seem like a frontend or wheel balance problem. I notice a slight shaking of the dash. But I dont feel any vibration coming from the shifter.

Thanks
Mike

 

Just an idea.....i had a similar problem with mine a while back...it was around 3000rpm i think, and it would do it in every gear, and in park as well, turned out to be a engine miss...replaced the plugs, wires, cap and rotor and vibration went away. just an idea for ya. mine almost felt like a wheel out of balance but that would only do it at certain speeds not certain rpm.

 

Hope its something simple the wires, that was going to be my next guess. I went into the garage the other night and ran the engine in the dark. I didnt see any arcing from the wires, I was kinda sad I didnt. But the other day when I was looking at it I heard a "snap" like a spark arcing while it was running. It only did it once and the engine never seemed to miss a beat.

Thanks

Mike