99 prerunner 3.4L 240,000km. At the start of the week my truck started to misfire, I found out that the misfire was in cylinder #3 so just today I replaced all my plugs. All of them had normal wear aside from #3....when I went to pull it the plug was quite a bit easier then the other plugs. The plug was burnt up pretty bad and the ignition coil was covered in brown paste. Fired the truck up, all runs good shake and sputter is gone. Driving around town for a few hours, all is good but when I went to head home coming up a steep hill i stepped on it and my check engine flashed again. I drove around the block a few times and it wouldnt come back on so i decided to try gunning it up the hill again and sure enough the light started to flash again, I cant feel or hear the misfire anymore. I hand tightened my plugs to about the same as they were when i pulled them out. Any ideas why im getting a misfire again when going up this steep hill? Should I worry about it?

 

Brown paste?..Leaking oil from the valve cover down the spark plug tube?..If so it could cause the spark to short before going through the plug,causing the missfire.

 

Maybe brown past was a little to much....its a thing layer of brown, similar to the black carbon you get if you were to hold a flame close to something. I'm a pretty big noob when it comes to mechanics but im trying to learn. Where would I start if im leaking oil from my valve cover.

 

Sorry for double post.

 

Heres some pics.

Coil #3, all others are clean
http://img504.imageshack.us/my.php?image=coilar6.jpg

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Plug, picture is blurry couldnt get it to focus. All the plugs have black sut on them with a little bit of white. JUST changed them they have maybe 20 km's on them.
http://img167.imageshack.us/my.php?image=plugmi9.jpg

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And finally the bolt to secure down the igniton coil on cylinder #3 only is covered in what appears to be corrosion?

http://img187.imageshack.us/my.php?image=boltkb3.jpg

Maybe this will help a little more.

 

The brown on the boot ended up being rust, water leaked in and caused a short. Replaced the boot for $20, sanded the ignition coil tip and cleaned the throttle body out while I was at it. Running smooth and flawless again....just in case anyone else ever runs into a similar prob I figured id post.

 

Where did you find the boot for the coil?