4x4Wire TrailTalk

Misfire - looking for suggestions

Posted By: Dryver

Misfire - looking for suggestions - 01/14/11 03:45 AM

Background: Degreased my engine three or four months back and sprayed it off, but apparently not very carefully. Started it back up and it was missing something fierce. Turned out water had gotten down around plug 4. Soaked it all up (along with the typical oil that ends up there too) and that pretty much solved the issue, with the occasional misfire on heavy acceleration.

Today, it decided it wanted to start seriously misfiring again, but this time on cylinder 3. I've pulled the coil packs and wires, found some more oil around spark plug 4 and cleaned it up. I tried testing the coils, but can't for the life of me figure out how to test the secondaries. If I test the resistance between the two connection pins on the coils, I get about .6 ohms on both coils.

Anyway, put it back together and it was still missing. Decided to test the coils by swapping them. Figured if the coil was bad, it would misfire on cyl 1 instead. I also pulled the plug from 3 and looked it over. Didn't seem too bad, and I just changed the plugs about 10K ago.

Fired it up, and it's still missing on 3. The plug wire going to 3 seems to have appropriate resistance when compared to the plug wire for cylinder 1, so I figure it's okay too.

Getting stumped here and looking for suggestions. Fuel injector maybe? Just ran fuel injector cleaner with a tank of gas a month or two back.

Thanks in advance
Posted By: Sportege_Panicmech

Re: Misfire - looking for suggestions - 01/14/11 08:22 AM

how did you confirm it was cyl 3? changing the coils and plugs and still being on three makes me lead to think it's signal to the coil issue but that would mean the other cylinder running off that coil would be missing too. Spray MAF cleaner into the intake and see if the misfire temporarily goes away and if so then it might be your #3's injector is clogged. if it remains the same then fuel inj. is not likely the issue. Remember that each coil fires two cylinders so if you're missing on only one for sure, everything up to your coil pack is likely good. I'd probably replace the spark plugs incase of a cracked porcelain insulator.
If your still stumped, you might want to try a compression check. compression is also key for proper ignition. but i doubt that's it.How do you know your other cyl is firing off the same coil? I thought my misfire was only one cyl years ago.. but it was two and it was a power wire to the coil pack. These motors can limp around town on 2 cylinders, but if you do, pull the connector on the misfiring cylinder's injector.. this shuts the injector off so you don't let raw fuel ignite in the downpipe and them burn up in the catalytic converter. Plus, you'll save fuel that is being wasted.. and no i dont think it would improve fuel economy over OE, lol. <img src="/forums/images/graemlins/lol.gif" alt="" />
Posted By: Dryver

Re: Misfire - looking for suggestions - 01/14/11 01:14 PM

I know it's cylinder 3 because that's what my OBDII scanner is telling me. I cleared the code before I started it up after switching the coils, but it still came back as a cylinder 3 misfire. No indication from the scanner that cylinder 2 is also misfiring.

I'll give your suggestions a shot and see if it gets me anywhere.

Thanks
Posted By: HarleyJohn

Re: Misfire - looking for suggestions - 01/14/11 03:23 PM

Swap the plugs like you did with the coil and see if it follows the plug or stays with the #3 cylinder.

It is almost always the 10 cent fix, not the 10 dollar fix and the plugs are the cheapest part of the system.
Posted By: Dryver

Re: Misfire - looking for suggestions - 01/14/11 05:36 PM

Will do, thanks.
Posted By: logansportage

Re: Misfire - looking for suggestions - 01/14/11 09:01 PM

When you have it apart, pull the boot off the coil pack and inspect the end for cracks. This was the same symptom I had when I had a coil with cracked plastic end. Under load or higher engine temps the crack will spread allowing for a loss in spark and a misfire. When you let is sit there and idle it would not throw the code. However, as soon as you put a load on it, pop there comes the code.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Dryver

Re: Misfire - looking for suggestions - 01/14/11 10:29 PM

I did actually pull the boots off of both coils and cleaned everything up with electronics cleaner before I reassembled it. I believe there may have been a slight crack on one of the coils, but the fact that the same cylinder misfired after I switched the coils makes me think that's not the culprit. I also bought a new coil "just in case" with the intention of returning it if I don't need it.
Posted By: Dryver

Re: Misfire - looking for suggestions - 02/02/11 12:49 PM

Update: I bought new NGK Iridium plugs at Autozone (they were out of the standard copper). Gapped them to .044 per what the guy at the counter said. Took it for a test drive and it seemed to run well until I got home and let it idle a bit, then it started acting up again.

I've been driving my wife's car for a week and a half or so, since the weather had been a tad on the cold side and she is recovering from surgery. I bought some new plug wires from the dealer (about $12 each) and I pulled it all apart again a few nights ago. Regapped the plugs to .030 based on some info I found elsewhere and swapped out the wires. It's been running perfect since them. I'm keeping my fingers crossed!

Thanks for all the suggestions.
Posted By: londart

Re: Misfire - looking for suggestions - 02/02/11 06:22 PM

on platinum and iridum plugs it is actually recommended to not gap,thats what the bottom # on an ngk plug is,the factory set gap...if you scratch the surface you can actually cause a misfire...there is a lot of people and so called countermen @ parts stores that still tell you to gap these...if they were properly trained like we train our counter people they could tell you this
Posted By: Dryver

Re: Misfire - looking for suggestions - 02/03/11 12:47 PM

Quote
on platinum and iridum plugs it is actually recommended to not gap,thats what the bottom # on an ngk plug is,the factory set gap...if you scratch the surface you can actually cause a misfire...there is a lot of people and so called countermen @ parts stores that still tell you to gap these...if they were properly trained like we train our counter people they could tell you this


This is from NGK's website FAQ:

Q: Do I need to set the "gap" when installing a new set of plugs?

A: Maybe. A spark plug part number might fit hundreds of different engines from many different manufacturers. Although the NGK factory will set the gap to a pre-selected setting, this may not be the right gap for your particular engine. The incorrect plug gap for your engine can contribute to a high rate of misfires, loss of power, plug fouling, poor fuel economy, and accelerated plug wear. It is always best to check the gap against the manufacturer's specifications. If adjusting the gap on fine wire or precious metal plugs such as platinum or iridium be very careful not to apply any pressure or prying force to the fine wire center electrode or insulator as they can be damaged. The gap should be adjusted by only moving the ground electrode.

So it seems the manufacturer thinks it's okay to gap their platinum and iridium plugs.

On another note, the CEL came back on. I think the unburnt fuel from the misfires fouled my o2 sensor(s). Looks like more work ahead. Yeah!
Posted By: londart

Re: Misfire - looking for suggestions - 02/03/11 05:34 PM

Quote
[quote]A: Maybe. A spark plug part number might fit hundreds of different engines from many different manufacturers. Although the NGK factory will set the gap to a pre-selected setting, this may not be the right gap for your particular engine. The incorrect plug gap for your engine can contribute to a high rate of misfires, loss of power, plug fouling, poor fuel economy, and accelerated plug wear.

This is the reason we usually recommend using OE manufacturer for plugs...in our case ngk which has a preset gap of 11mm or .43-.44 which is what is recommended for our engines <img src="/forums/images/graemlins/cheers.gif" alt="" />
Posted By: Dryver

Re: Misfire - looking for suggestions - 02/03/11 08:18 PM

Interestingly enough, there is conflicting information on Kia Tech Info.

If you look up the repair procedures under the Engine Electrical System/Ignition System/Spark Plug for the 2001 model year (and maybe others, too), at one point in the "installation" section it states that the gap should be 0.039-0.043. It also states this in the specifications.

But further down in the inspection section, it states the gap should be 0.028-0.031.

I saw a moderator on another Kia forum recommend .030, so I went with that for now. If I open it back up again at some point, maybe I'll gap it back up to .042 and see if it still runs smooth.
Posted By: Sportege_Panicmech

Re: Misfire - looking for suggestions - 02/04/11 07:23 PM

I'd imagine a smaller gap would run smooth, but not as powerful. A larger gap would be powerful moreso, but risking misfire or rougher run underload??? this is my guess. Anyway. Mitchel1 OnDemand at the shop I work at confirms .039-.043. I can also attest Londart's Credibility. He's our parts guy at the shop.
Posted By: Axe Man

Re: Misfire - looking for suggestions - 02/05/11 07:35 AM

The correct gap is indeed 0.039 - 0.043 (1.0 - 1.1 mm). I would re-gap them back to the correct spec.

If the misfire returns and the replacement/swapping of the coil packs and plugs haven't fixed the issue it's time to look for other causes.

If you are finding oil on any of the plug threads replace the valve cover gasket. Perform a compression test on all the cylinders. They should be within 10% of each other.

Other possible causes: Bad fuel injector (not very common), cracked exhaust manifold (very common). To see if the manifold is cracked remove the heat shield surrounding the O2 sensor.
Posted By: logansportage

Re: Misfire - looking for suggestions - 02/07/11 09:56 PM

A trick I learned to check if you have micro cracks or a leak in the gasket for the exhaust or intake manifold is to spray carb cleaner or starting fluid (ether) in the area around the exhaust or intake manifold. It is highly advisable to do this when the engine is cold and just started. When it gets warm it works too, but you need to be careful not to use too much because you can cause a fire. Carb cleaner and ether are not as flammable as alcohol and will plug the crack for a second or two. This gives you enough time to see if it starts running smooth again.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />
Posted By: Sportege_Panicmech

Re: Misfire - looking for suggestions - 02/08/11 09:14 AM

my xhaust mani is cracked, and has a small buildup of black around the crack, but it's been this way since I've owned it. runs great. Crack isn't big enough to cause any noticeable exhaust leak noise. (ie: pfft pfft pfft) ya know..
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