93 lumina 3.1 spark plugs issues

4 days ago I replaced the plugs and wires on my car. The previous owner informed me that the wires were bad and the car wouldnt start after it rains. sure enough, after sitting for 2 days in the rain, it wouldnt start without a jump. I already had new plugs and wires, just had been too lazy to replace them. So, I got off my duff and did the work my self, being SO careful not to cross the connections. Before I started the engine ran very smooth, now it idles rough, and you can feel it when you accelerate. Now when driving I feel surges of power like some of the cylinders are firing erratically. Sure that I had managed to screw up the wires, I researched the firing order on autozone.com, traced each wire from the coil to the plugs, and all were good. When I did the installation, I had to call for the correct gap for that car and was told .045". Out of the box they were in between .045" and .050", I checked each one with a circular type guage. Since the ones I pulled out had a MUCH larger gap, I figured it was good. I also put a small dab of silicone into each end of the wires. I am told the silicone is not the problem. I checked each wire for a good seat on both plugs and coil, no effect. I am assuming that the gap is the problem, but where do I go from here? Do I make the gaps bigger or smaller? I am not paying good $$$ to have a mechnic fix my mistake, I'm at a loss as to what to do next, any advice is greatly appreciated, thanks!

I ran into a similar problem when I last replaced my plugs. In my case, the problem turned out to be that I cracked one of the plugs upon installation, as it's easy to do on the rear bank.

Don't discount the obvious.... that you could have gotten a bad plug or wire even though they are new.

If it wont start when its wet its because the ICM/coil packs are shorting. Sometimes when it rains here my car will run on 4 at the low end until its warm enough to dry up all the water that got in there, then its fine. I dont see it as being a problem for me yet cuz it at least stil runs when it does this.
Take out the coil packs and ICM and clean up the connections really well. Then put some dielectric grease on the tabs that plug into the coil packs.
Might be a good idea to have them tested as well while you've got em out.

The placement of the ICM was kinda a bad idea, being right in front. There you have rain coming in via radiator, roadsplash, and anything else that water can think of. I once drove through SHALLOW water (not even half an inch) and enough splashed up on the ICM to kill the car for a minute. I appreciate GM's later idea to move them to the back of the engine, though if you have bad ws at the firewall end of the hood similar could happen.

The placement of the ICM was kinda a bad idea, being right in front. There you have rain coming in via radiator, roadsplash, and anything else that water can think of. I once drove through SHALLOW water (not even half an inch) and enough splashed up on the ICM to kill the car for a minute. I appreciate GM's later idea to move them to the back of the engine, though if you have bad ws at the firewall end of the hood similar could happen.


These coils will fire across a 1/2" gap if allowed, so the gap is NOT the problem. I agree there is most likely a cracked insulator on one plug. Very common mistake if you are not someone who does this stuff daily. Might want to investigate the condition of the module, and the coils' connections to it also, given the no-start in rain you mentioned. You might try misting water from a spray bottle near the ends of the plug wires while running, to see if you can cause a misfire, then you'd know which plug was the problem.

Well folks, thankyou all very much for the advice. I wasnt able to get online the past two days, so I couldnt see that your advice was right on the money. I ended up ripping it all apart, and re-gapped all the plugs just to be sure. The last plug I pulled, #1 on the backside of the engine, pieces of porcelain fell off as I took it out of the socket. I must have hit it too hard with the air ratchet when I put it in the first time. I didnt know about the rocking the engine forward trick, so I actually took off the alternator to get at the plugs. That still didnt leave me much room to work with, so I though the air would get at them easier. I learned that little trick from you guys here, and WOW what a difference, all the plugs were right there easy as hell to get at, thanks again everyone! -Ryan

FYI- Don't install plugs with an air ratchet, especially on aluminum heads. Just asking for disaster.:sly::nono:

Seen guys run plugs all the way through the casting and into the combustion chamber.:eek7: