Ignition repair on 1995 GMC Suburban
My 1995 GMC Suburban has had a bit of a stumble for a while now. It runs fine most of the time but will occasionally hiccup and stumble. However lately it has gotten worse and towing the trailer has been a bit of a struggle.
I began by replacing the distributor cap and rotor. The cap is held in place by two Phillips head screws. It seemed a #1 Phillips fit better than the more common #2. I swapped the wires over to the new cap one at a time to make sure I did not mix any up.
Before installing the new cap I installed a new rotor. The center of the old rotor was obviously burned. I just pulled up on the old rotor to remove it from the distributor shaft. The new one pressed on by aligning the tab in the slot and pressing it down on the shaft.
I then set the new cap in place and tightened the two screws. I made sure all the plug wires were properly routed and started the engine to test. Most of the stumble was gone but it was still down on power when towing.
When swapping the wires, I noticed the coil wire looked especially bad. When the truck started running really bad on the way home from Harlan, I stopped at Advance Auto and picked up a new set of wires. I swapped the coil wire in the parking lot and headed back out. The engine immediately ran better. I had had trouble starting from traffic lights but that problem went away pulling out of the Advance Auto parking lot.
I waited until I got home to swap the rest of the wires. I was happy that the set included all the proper length wires. Sometimes these lower cots sets don’t have the right length wires but all these fit nicely with a couple being an inch or two longer which made routing easy in the factory clips.
I laid out the wires on the shop floor in order of length. I then pulled off one wire at a time and picked the corresponding length wire to replace it. I did open up the loom clips and release all four wires form one side of the engine at a time. However, I only had one wire off the distributor cap at a time to avoid switching any wires.
The four original wires on the passenger side had extra protective sleeves on them. I transferred these to the new wires. These sleeve help protect the wires where they go behind the transmission dip stick. I put all the wires back in the separator clips and made sure they were routed away from heat as much as possible.
Several of the wires were burned up where they connected to the spark plugs. I noticed that the engine idled smoother and revved up smoother after I swapped the wires. I will have to wait for a test drive under load to know how much the new wires have helped.