The Stovebolt Site Forums The Shop Area Engine Shop Replaced spark plug wires, now truck studders under heavy exceleration...

What a fun night!! I drove my truck around real quick in between "Wife" errands and it studdered or missed under heavy exceleration. I changed my spark plug wires last night. What gives? I will put the old ones back on tomorow night after work but I was just curious as to why this has started. This truck is all stock, GMC 228, but upgraded to 12 volt. Maybe this is just a new issue regardless of the plug wires, but the truck has always ran great. I still had fun running around in rush hour traffic!!

Thanks!!

How dirty/plugged is your fuel filter?

Sounds like you got a wire crossed when you installed the new ones... Check the firing order..

I think bill is right on with the crossed wires.BEEN THERE DONE THAT...and thats how mine ran.Let us know what you find.

How well does the engine run at idle?
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The wires being crossed (wrong order) would make it run poorly at idle. It may be possible though.
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The correct firing order is 1,5,3,6,2,4.

UPDATE: Truck runs great at idle, tonight or over the weekend I will check the firing order and make sure all plug wires are correctly installed. It looks to be a real chore finding out the firing order on the distributer, but I think I understand how to do it, with the top dead center and lining up the timing marks on the flywheel in all. Any Pointers?

Also, I figured I might want to run my ohm meter on all plug wires to make sure they are all good. What do you think?

ALSO, I heard that if all is well the number one spark plug on the dist. cap it will point to the number one spark plug. Is this true?

Ohms on the wires should be between 4k to 8k per foot of wire.
WIth the #1 piston at TDC, and the ball in the flywheel lined up with the pointer in the hole in the bellhousing, look to see where the rotor is pointing. Start #1 plug wire at the point on the distributor cap where the rotor is pointing. The rest of the wires on the cap will go in a clock-wise direction on the cap 1,5,3,6,2,4.
Have you looked at the point dwell (point gap)?
Gap should be right at 16 to 18 with a CLEAN feeler guage. If you use a dwellmeter, the reading should be 32 to 36.

UPDATE!!!! Ok, tonight I lined up timing mark on flywheel housing with flywheel. Then I pulled my dist. cap and checked location of rotor. Then I put my cap back, located number one spark plug and wire and then checked firing order. Everything is the way it should be. I pulled the new spark plug wires off and put the old, crusty, dry-rotted plug wires back on and went for a ride. THE TRUCK DROVE PERFECT!! No studder under load, smooth get up and go. Bad set of plug wires? I dunno. Installed/seated fully? I think so. I should just keep the old tired plug wires on but they are in pretty bad shape, but the truck does run good with them.

Got any good part numbers for plug wires for my truck? I like the plug wires with the metal on the end with no boot, I guess you would call them "Old school" wires.

Thanks for everyones help here in this chat room!!!!

Are your new wires resistor wires ? Do you have a 12 V system with a six volt coil ? You may have new wires that break down and arc on your setup. The shuddering under heavy load can result when the ignition can't fire the plugs properly when there is more air/fuel in the cylinders.

I got some of those old school wires at Chevy Duty.

Have you compared the resistance of the new wires to the matching old wires?

UPDATE: I went ahead and installed a second new set of spark plug wires, and the truck runs great now. I guess either that was a bad set of wires or just one was internaly damaged.

These old trucks sure are fun!!!!