1996 GMC pickup truck 4.3 L

I have a 1996 GMC Pickup truck that has a 4.3 L engine. I keep getting an engine misfire on my check engine code. One mechanic told me to change my plug wire and plugs so I did. That did not help. I then changed the distributor cap and rotor, that helped for awhile, but when it is rainy or damp outside the problem returns. I looked under the hood at night and I have a blue glow around the ignition coil. I replaced the coil and the new coil has the same blue glow around it and the engine is still misfiring???? Any help would be appreciated. Did you make sure all the wires are secure and not rubbing something else? If so, I would replace the coil again. While doing so, Make sure it has good grounds, such as where the bracket meets the intake. Also, Make sure the ground cable and ground straps are in good shape and secured to the battery and frame.


-RickyRiot Whats the code number/s My guess - P0300 Random Cylinder Misfire

betcha lunch on it. Is this a vortec, with the central fuel injection system and possible intake manifold leaks? What do they call it, cpfi? Crappy port fuel injection? RickyRiot wrote:My guess - P0300 Random Cylinder Misfire

betcha lunch on it.


That is what it was random cylinder misfire Hmmmm, gotta try to figure out which cyl/s are misfiring and whether its ignition,fuel, vacuum, compression, wiring problem or controls(pcm) related The damp/wet thing almost makes you think ignition problem, but you've replaced all that huh? Wires,plugs,rotor,cap,coil? The only other things I could think of that relates to getting "wet" would be to check the rubber seal that keeps water coming off the windshield from entering the engine compartment and dripping on your dist cap. Another thing to check is to see if your fenderwell splash guards are in good shape, a lot of times people will rip these out when doing ft end work or replacing spark plugs, allowing water off the road to splash up on the spark plugs? You could ground out or pull off each plug wire at the dist cap and see which ones have "no rpm drop". This would indicate which cyls aren't pulling their weight or doing anything? Then go from there, compression test, check the fuel pressure/injector curcuits/wiring, check for an intake leak, etc.. jmaninfior wrote:I looked under the hood at night and I have a blue glow around the ignition coil. I replaced the coil and the new coil has the same blue glow around it and the engine is still misfiring???? .


This is the part that is still bugging me. I gotta believe the blue glow is spark - And a coil arching to the intake or the coil wire would definately explain a P0300.

jmaninfior, got any updates for us? The blue glow is the coil trying to take a different path to ground than what was intended. Electricity will take the shortest path of least resisitance. So the problem lies from the coil on.

You said the mechanic changed the plug wire?? Is that singular?? Make sure the whole set is changed with what was intended for your vehicle. Plug wires have different resistance values.

Even though you replaced the cap, take it off at night and have someone crank the engine. See if there is blue arcing. You could of replaced a bad cap with a factory defective one.

Check the quality of your grounds like Ricky said. This includes the negative from the battery to the block and the chassis ground strap and the grounding at the coil itself. This one makes the most sense as it seems the power is bottle necking at the coil.Car Repair Talk's forum.