Slight miss at idle to 1800 rpm......

[98malibu3.1]

Causes? I completed my LIM swap a couple of weeks ago and when I was done, CEL code "cylinder #6 misfire detected" popped up. I erased the code and it hasn't popped back up since. Now I have the aforementioned miss on one cylinder. I checked the gap on all 3 front cylinders and they were tighter than normal. Stock is .060 and they were sitting around .050-.052 I regapped them and stuck them back in. Still the same. Number 4 had some unusual deposits on the ground electrode that had me worried somewhat. Never seen them before like that. The plugs are NGK's and they're not very old. It's very annoying and aggravating. What do you think the chances of it being a coil or that plug? Any tips on trouble shooting w/out getting the hell shocked out of ya?? LOL

[19Cutlass94]

yeah if you wanna check the coils, get a pair of INSULATED pliers and with the car running take the wires off the coils... if its good youll see a nice spark

[tractorman]

Don't pull plug wires on this engine. The problem with that method on a DIS system is that you're canceling out TWO cylinders. It won't tell you much of anything. Here's an easier and safer method of cutting out cylinders:

Get 6 paper clips. Remove each plug wire from the coil, and insert the paper clip (bending appropriately) so that the wire goes between the terminal and the boot, and will stick up when you snap the wire back on the coil. Make it so that a paper clip sticks up for each cylinder, and so they they don't touch (or come too close). Now take piece of any ol' wire you have laying around and ground one end anywhere on the engine block. Strip a bit of insulation off the other end. Start the car, hold that ground wire with a thick glove, and ground each paper clip one at a time. This will cut out only a single cylinder, and it won't shock you.

Since you've just done a LIM job, I'd be looking at things like plugs, wires, and injector wiring. I had some intermittant miss problems on my '01 Lumina after I did the same job- long story short, one of the new plugs that I'd installed was bad, AND the seals for the injector connectors just didn't seal well- causing an arcing problem whenever there was moisture. One new plug and 6 blobs of dielectric grease took care of the problem.

[98malibu3.1]

Don't pull plug wires on this engine. The problem with that method on a DIS system is that you're canceling out TWO cylinders. It won't tell you much of anything. Here's an easier and safer method of cutting out cylinders:

Get 6 paper clips. Remove each plug wire from the coil, and insert the paper clip (bending appropriately) so that the wire goes between the terminal and the boot, and will stick up when you snap the wire back on the coil. Make it so that a paper clip sticks up for each cylinder, and so they they don't touch (or come too close). Now take piece of any ol' wire you have laying around and ground one end anywhere on the engine block. Strip a bit of insulation off the other end. Start the car, hold that ground wire with a thick glove, and ground each paper clip one at a time. This will cut out only a single cylinder, and it won't shock you.

Since you've just done a LIM job, I'd be looking at things like plugs, wires, and injector wiring. I had some intermittant miss problems on my '01 Lumina after I did the same job- long story short, one of the new plugs that I'd installed was bad, AND the seals for the injector connectors just didn't seal well- causing an arcing problem whenever there was moisture. One new plug and 6 blobs of dielectric grease took care of the problem.

Can you possibly post a picture of what you're talking about w/the paper clip thingy? Plug wires can be ruled out as they were replaced when LIM was done. Plugs, I may swap those out and see what that does. I figured that if a coil were going bad, it would run a lot worse since it controls 2 cylinders.

[98malibu3.1]

Ok, swapped plugs and made sure the new ones were gapped properly (.060) and the misfire is still there!! Well, I don't know if it is or not?? It sounds as if the miss is intermittent, but is really prominent @ 1800 rpm. HELP!! I can feel the engine shake like there's a miss but it doesn't sound like it....suggestions??

[tractorman]

You can narrow down which cylinder has the problem using the aforementioned paper clip technique. Sorry... don't have a picture.

If you're going to throw parts at it, then wires are the next thing to try.