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Cylinder 5 was misfiring, so i replaced plugs, wires & coil pack. still misfires (so far mainly from cold start it seems). not really sure where to go from here, any ideas?

What brand of plugs and wires did you replace them with?

The 3800 can be a fussy bastich regarding these 2 things.

Did you get a check engine light and had a code read for that?

What about the coil pack, did the old one test out bad?

Here's a link for testing/trouble shooting coils.
http://www.pontiacbonnevilleclub.com/fo ... c1683.html

Champion Platinum plugs, (I cant remember what brand wires). Yea I kept getting p0305 & it'd misfire, not as bad as before I changed everything out. Never tested old coil, just kept getting p0305 so i figured replace coil, plugs & wires, meaning I've already replaced 1 coil & miles are up there.

What plugs/wires is recommended with these cars?

Platinum plugs and our ignition systems don't get along. NGK or Autolites for brands, regular copper or iridium, copper is way cheaper per plug but you get more mileage out of the iridium ones.

For wires a majority of guys in the club run the Napa Belden wires. They have a lifetime warranty and are a good quality set of wires that will support even built up motors.

Also make sure that the wires are ran in their wire holders and are not resting against any sharp edges or really close to the O2 sensor wire.

If a good tune-up doesn't cure it, you may want to check the injector or in an unusual but not unheard of case, a broken valve spring.

Bing wrote:Platinum plugs and our ignition systems don't get along. NGK or Autolites for brands, regular copper or iridium, copper is way cheaper per plug but you get more mileage out of the iridium ones.

For wires a majority of guys in the club run the Napa Belden wires. They have a lifetime warranty and are a good quality set of wires that will support even built up motors.

Also make sure that the wires are ran in their wire holders and are not resting against any sharp edges or really close to the O2 sensor wire.

Thx, I'll swap plugs to ngk or autolites & see what happens as well as rechecking to make sure the wires are ran fine & swap different wire just to see. Weird being intermittent

Carefully go over the routing of the replaced spark plug wires. The wires should be routing to never have one wire cross over another. Crossed spark plug wires can result in a misfire.

So I swapped fuel injector #5 with #3, changed plug #5 again, swapped wire out & it still misses on cylinder 5 intermittently. Oh also checked for broken valve spring, rechecked wires so no crossing, as well as o2 wire not touching bracket. Anyone have any more ideas of what could cause it? After swapping injectors, it ran fine for a day & a half, then p0305 came up again today & its been off & on.

So before I go to work, it was missing, shut it off, 30 minutes later i go to work, its running fine to work. Get off work, come out, its still missing, goes away after a short time & drives fine coming home (when i started going home it was missing, then stopped about 5 minutes into my drive home) & ran fine after that. Any ideas? Gonna get ICM tested this week soon as i have time, not sure where else to look at

Static wrote:So before I go to work, it was missing, shut it off, 30 minutes later i go to work, its running fine to work. Get off work, come out, its still missing, goes away after a short time & drives fine coming home (when i started going home it was missing, then stopped about 5 minutes into my drive home) & ran fine after that. Any ideas? Gonna get ICM tested this week soon as i have time, not sure where else to look at

Did you switch coil packs to see if the misfire moved with the coil?

Yeah this is 3rd coil pack I've tried, also swapped icm. Still getting misfire cylinder 5. Usually only happens 1 or 2 times a day. Clear code, wait a few minutes, restart & it goes away. Starting to wonder if maybe its an exposed wire meaning its happening intermittent & have changed, plugs, wires, coil, icm, checked plug wires & o2 wires to make sure they aren't hitting anything or wrapped around anything. Also just cleaned MAF sensor.. Think just to rule it out & because its time gonna do fuel filter too. Misfire isn't real bad, & usually doesn't last long, but very annoying when it happens.

Have you looked at the wire loom that serves the ICM, cam sensor, and crank position sensor. It has a plug connection that snaps into a bracket between the UIM and valve cover (plug "A"). The harness then runs along side the valve cover and plugs into the ICM.
I wonder if any of those wires are damaged inside the loom that serve the ICM?



Just a thought here, plus it's one that doesn't cost money to do.

I will have to check that before work tomorrow. I did notice some exposed wires going to injector 3, just looked like the rubber had gotten hot & melted so i taped them. I'm going to have to pull that plastic shielding off & check rest of it meaning its missing on cylinder 5. Funny tho, ran fine up until I left work, then missing about 5 miles on drive home then ran fine for rest of ride home about 15miles.

Any chance it could be something stupid like a really cracked belt or fuel filter? I looked at belt today & its bad & its time for fuel filter. Because if it's missing, it will go away within like 5-10 miles or sometimes just shutting car off for awhile. (i do keep scanner hooked up so I can clear it when it comes up)

You can give the fuel filter a try if it hasn't been changed in quite sometime.
Just not sure at this point what the culprit is.

Remember with the fuel filter, to let it spin as you're loosening it. Most likely the nut has rust welded itself to the filter, and there is the potential the o-rings inside the snap on connector won't seal like there supposed to. You can replace the o-rings or just buy a fuel line repair kit.

I'd do a compression test on #5, just to rule out mechanical failure, if you don't find anything wrong with the wiring harness for the injector.
A DMM would be handy, most have a continuity test function, in case a wire is broken inside the colored insulation and you can't see it.
Or, use a one of those mini interior light bulbs with the flat base in place of the injector while it's misfiring (leave the car running when you remove the connector from the injector to install the builb), it will blink if the injector wiring is okay.

So, to clarify (correct as needed):
When you start the car cold, it misfires lightly (enough to be felt, but isn't having a major effect on performance) and the PCM is setting a code for the misfire. Once the engine gets up to temperature the misfire will go away on it's own? While it's misfiring, if you stop and clear the code, and restart then the misfire does not re-occur. Or if you let the car sit for a few minutes after you start it cold and it's misfiring, it will not occur even though the engine is still cold and the code was not cleared?

That would indicate a non-intermittant misfire, because it's repeatable under certain conditions (cold start).

Yea, I'd say about 40-50% of the time (lately after work 9pm or so) it will misfire (since 1st icm & 2nd coil replacement last weekend), not a bad misfire, enough to cause car to be sluggish & shake a little around now & then if driving. Sometimes it will go away while car is still cold. If i clear code & shut car off before it comes back on, most times it will miss again for a little while, time can very, but usually i can wait 5-15 min & it'll go away on its own or with me clearing code. If it stops missing & I clear code & restart car, its fine (cold & warm). When misfiring it does take a little while longer to hit 14 volts on gauge, about 8 seconds. But it doesn't always miss from cold start, everyday before work its been fine so far (i leave around 1130am) but getting off work lately its been missing.

Any chance of this being an o2 sensor? I've only had car about 4k miles & it has 215k miles on it now.

Haha kinda funny, wired checked out fine going to injector. The ICM I put on the car was used, it also came with coils, so i kept them on. Took 1 of my old ones i replaced before (about 2 years ago) & put it inplace of 2/5. Ran 1/2 can of seafoam through intake, no misfire symptoms so far, been a bout 6 days. Check Engine has came on throwing misfire cylinder 2, but like I said no symptons of a misfire. Gonna get another can so I can use half of that one, that way a full bottle went in to clean it.

I am having the same problem with my car. I had auto zone run a code scan on it. I came back as a misfire on cyclinder 5. I have replaced all the plugs. it has new (within the last 2 years) wires and one new coil pack. I tried moving the coil packs around to see if one was bad but still had the missfire. all the plug wires are running where they should be. I am wondering if the fuel pressure regulator is failing? I have concidered replacing the #5 fuel injector but haven't yet due to cost. I haven't ran a compression test but feel that isn't the problem. The car has 133,000 miles on it. some other things that i have done to the car since i got it (two years ago) are.
new head gaskets
new upper intake manifold
new fuel pump
valve job
new pcv