ok, i have had this problem w/ my car shaking and studdering. i talk to a buddy, he says, new plugs, wires, cap, and button. i do it. then it still is doing it. i take it to a mechanic he says timing was off and charges me 30 bucks. i pull it off the lot, and its still doing it. i take it back and he says i'll get to it next week. then next week he says the wires i put in were on the manifolds. 20 bucks he charges. now i bought new wires and installed them so none are touching the manifolds. its still doing it. does anyone have an idea? no mechanics can get to it for a couple of weeks. thanks

 

It would help if you describe the car, but I would say possibly the IAC if it only does it at idle speeds. Give us some more specifics.

------------------
1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, Accel coil, 180 t-stat, Bald Eagle tires,
Hypertech fan switch, Accel 23# injectors, Holley AFPR, ported plenum,
Ruger P95DC, hot wife, new oil filter, thick rubber floormats.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

 

My car seems to be doing the same thing - I am very interested as to what others think. I have an 84 Z/28 - 305 (carb - not fuel injected), 5-speed. Just recently at idle the car has a nasty vibration. As soon as I start moving, it stops. And unless the car is completely stopped, I don't even notice it. I gave the car a major tune-up (cap, rotor, plugs, wires, all fluids, cleaned and retuned the carb) but nothing seems to affect it. I don't believe it is the engine that is causing it. And it does not make a difference in vibration if the clutch is engaged or not. So I don't think it is the clutch either. Someone mentioned the IAC?? What is that? Where is it located and how hard is it to replace? More importantly, how expensive? Thanks for any help.

 

sorry i forgot to add that. its an 88 iroc w/5.7 tpi. thanks oh yeah, whats the IAC?

 

Idle Air Control valve, located on the throttle body. It's a pintle valve with a stepper motor in it that adjusts the amount of air taken into the engine at idle. If it sticks or is malfunctioning, it can cause some of the symptoms you described. Also, is the actual engine idle speed jumping or is it just the tach? What speed does it idle at? Does it act up when first started, warmed up, or all the time? Sorry for all the questions, just wanted to give you a good answer and need more info.

 

well right when i start it, it starts with the jerking, but it get real bad when i put it in drive. it all goes away when i put it in reverse also. when im driving its like the car is jerking back and forth. when it is doing this the rpms are like jerking down. the motor is shaking fast too. thanks

 

Try checking the rotor as well as underneath your distributor cap.

[This message has been edited by 86z/92rs (edited July 05, 2001).]