car bucking
 

my 89 gt is not running right at no load situations. I cruise down the highway and under 2k it really bucks Like it is missing then its alright then missing again. Almost like the timing or the fuel mixture is changing under the same conditions. I had this problem before but it went away when I changed plugs and wires and put 89+ octane in it. I started puttin 87 in and it got really bad all of the sudden. Also I does not idle well any more up and down almost stalls then it catches its self What should I look for Thanks

does it get worse when you step on the gas a little, then better when you let off the gas?

No it tends to get better when I hit the gas and worse the more I let off. But what were you thinking I'm open to ideas

my 92 has an extremely similar problem and i have yet to find what it is. Does yours start to backfire in the intake manifold? The list of things that i have changed is too long to say. Im told that th problem might be either the coil pick-up or a feul pump going bad.

No mine does not backfire though the intake. It just jerks and hesitates

sounds like a coil, or coil wire.

Thats the weird thing the coil was replaced with an MSD coil

What's your timing set at? If it got worse when you put 87 in it, could be timing. Also could just be bad ignition parts. Could be coil, could be TFI module, could be the pickup coil in the distributor.

well then i would say u-joints, but with what you say now its not, check your vacuum lines that would cause shuddering at idle.

well i know i can feel my e-cam bucking my car a little, at a slow roll in gear......reason why i said coil wire, is cuz i had one go bad, but the wire was burnt inside the boot, and i didnt know until i pulled it off one day and it fell apart, i guess you could start on simple things, like check timing, cap and rotor ect... good luck

Well here is what I found. I disconnected the idle controll valve and then the idle settled down so Its not a vacum leak. The rotor cap, wires, plugs, coil are all less then 5 months old. Where is the TFI located is that the ignition module. I also tried pulling the ignition timing conector( the little plug you pull to set the timing) so the timing would not change. And it got worst, the bucking that is. Now timing I had just recently moved my timing back when I began putting 87 in it. Question first what controls the Idle control valve and second how can I make sure my coil is well grounded to the block.
Thanks

your coil should be fine, if it wasnt grounded, or was failing, it wouldnt start at all, they usually just go bad, not gradually.

I would clean the iac real good, and invest in a code scanner, they are like 30$ from autozone, it might give you an idea where to start.