Odd 3.4L spark plug problem

[ig2011]

I have a 1998 4runner 4WD 3.4 auto 298,000 miles. A couple months ago i got a P1300 code and a rough idle. I brought it to the dealer and they replaced the spark plugs with new. 2,000 miles later, the same thing happend, they replaced the plugs and it worked fine again. Now its been 1,500 miles and the same thing happend. So i changed the spark plugs myself to NGK copper double grounded, and it seems to be running better then it was with the dealer plugs. WHen you look at the old plugs they look almost new, and show no indication of obvious failure. Has anyone encountered this problem before? I beilive the ones they installed were 6 K16TR11. Thanks

 

[T4R_Finally]

Maybe not the plugs at all and you have a wire that is somehow working itself loose? Were the wires changed during any of the plug changes? Maybe you have one that is not holding well and when you change the plugs and put the wires back on, you are really fixing the wire issue and it has nothing to do with the plugs. Especially if the plugs are all looking none the worse for wear when you take them out. If/when it happens again, pull and replace the wires and see if it goes away. If it does, replace the wires.

 

[quicksilvr]

Wow, I'm surprised a dealer tech can't figure this out. One of the coilpacks or wires is bad. Every time they take them off and put them back on, it makes good connection...but then loses the good connection in a few miles. The plugs are not the issue. You need new wires, and maybe a new coilpack. If the coilpacks are originals, and have 298k on them, I would just spend the money and get 3 new ones. I err on the preventative side though.

 

[ig2011]

Good point! The wires were replaced about 5k miles ago. I could see on the middle cylinder of the right bank that one coil pack was new, so i figure they may have been using it for diagnostics and forgot to take it out, since they did not charge me for a coilpack.

Between putting these new spark plugs in and first having the problem, i removed all the plugs and inspected them and put them back in, still having the misfire occur. But i suppose there is probably nothing consistant when it comes to the problem which is intermittent.

 

[T4R_Finally]

I think you just narrowed down the problem by talking out the details in this thread. You've got new wires, relatively, new plugs, but maybe 1 new coilpack. I'd do the coilpacks next and see what happens.

 

[Devious81]

Replace the coil packs. They're probably worn out. If you still have a misfire after the coil packs are replaced, then you may have other, more expensive issues. Have you compression tested the engine yet?

 

[ig2011]

It runs perfect right now, better then ever. Lots of power. I have not done a compression or leakdown test, but it would probably be a good idea with that many miles. It had been serviced regularly at the dealer until 293k when i bought it for $500 ;-)

 

[Devious81]

Damn, that's a steal for $500. Good find!

 

[PitbullRescuer]

$500? Damn, I have to pass the crown, I thought I stole mine for $2800.

I agree with the others, safe bet it's the coil packs.