Ignition coil or not????

[adrianMCmoreno]

Has anyone had an ignition coil work but fail at high idle? I'm having a spark issue or atleast I'm assuming I'm tired of throwing parts at it. It idles fine but as soon as I drive it it starts to not quite back fire but a small pop or should I say hiccup at around 30mph. If I rev it in park you can tell because it shakes.

It's a 350 tbi swapped to carb, heads have had a valve job new plugs wires distributor I've checked compression all cylinders are at 155.

Checked for vacuum leaks with brake fluid changed all hoses, even ran it in the night to see if it was arching anywhere and nothing.

Swapped carbs between a quadrajet and now a holley same problem Still there.

I need help before I blow this car up

 

[pontiacgp]

I would try another module

 

[fleming442]

Check the button underneath the coil. MSD makes a brass one. I would have never believed it could happen, but it happened to Hooptiewagon and I on Drag Week. The carbon button was cracked in half-$3 part...

 

[1320John$$$]

Sounds like the timing is late ck it

 

[adrianMCmoreno]

I would try another module

I've replaced module already

 

[adrianMCmoreno]

Sounds like the timing is late ck it

Why would the timing change all of a sudden though? I do have a hard time with the timing, the cover doesnt have a timing tab

 

[500/600]

Why would the timing change all of a sudden though? I do have a hard time with the timing, the cover doesnt have a timing tab

Get a timing tab first. Or at least find true TDC and get a pointer made of wire lined up with the balancer. With your timing light see if anything obvious is happening across idle to 3000rpm. May be worn out pins/bushings in the distributor advance, or a broken/missing spring in the same place, or a stuck weight. Do you have vacuum advance? Unhook it and see what happens.

 

[pontiacgp]

a couple of tests you can do....

 

[GuysMonteSS]

A worn distributor gear could also cause the problems you are having.
Might not hurt to pull the distributor out and have a look.
Guy

 

[airboatgreg]

Disconnect the vacuum advance. If it fixes it the wire to he pick up coil is broken