Well... Ol' girl is starting to show her age, I guess. Or is it?

I have 207k on this SR5 V6. Recently had the timing chain done, and after getting some serious miles out of some NGK Iridiums, I thought it was time to swap the plugs again. They were TOAST, but amazingly ran well and got decent gas mileage.

Tonight I replaced the plugs with Denso Iridium "Long Life" plugs (purchased from Advanced Auto and not cheap). Easy swap, with the exception of driver's side bank (of course), but no biggie. Gapped everything to .043 as suggested for these plugs.

Reconnected the battery and started it up. It did the usual rough idle thing until the computer caught up and then let it sit and idle for about 5, maybe 10 minutes. Ran perfect. Then I went for a drive and everything changed. It was pretty well up to temp by this time. And as soon as I put it under load I got a BIG stumble and the check engine light started flashing, VSC trac light came on, etc. Stumbled back home on less than 6 cylinders.

So, I checked my work. I went back through every plug again and checked to make sure something wasn't off. Re-torqued everything. Couldn't find anything wrong. So, I cleared out the computer (10 cycles of the key) and started it up. Ran great. Drove it around and it seemed good so I drove it down the road to put a squirt of gas in it. After getting gas, I sat for a bit idling and I noticed some strange noises coming from the ECU area (behind the glove box??). Like solenoids cycling, or something. Gremlins?? Pumped the brakes a couple times and it seemed to stop. Maybe a total coincidence and frankly, maybe it has always made these noises and I never noticed because I had music on. But, it got my attention.

Left the gas station and headed home. There is a long hill on the way home. As soon as I hit that hill and started loading up the drivetrain it started stumbling again, and by the time I got to the top I couldn't drive faster than 30-35 mph without it violently shaking. Drove it in. Parked it. Went inside defeated....

I don't have a code reader or anything to do a leak-down, so off to the shop (probably the stealership, because we're supposed to leave for a trip on Wednesday) and time is of an essence. And time is something I have basically none of, since we have a 2 month old baby and a 2 year old.

So any ideas? Did a coil pack suddenly give out when doing the plug change simply from handling it? Something ECU related? Crap plugs?? Doesn't seem like it would be a head gasket, since this came on very all of a sudden and it gets driven daily.

Let me know your thoughts. I'm fearing the worst and still trying to recover from the timing chain, so the timing (no pun intended) couldn't be worse. In fact, down right terrible timing for us.

Thanks for any input!
S

First thing I would do is put the old plugs back in. What's the part# for the new spark plugs that you installed?

sk20hr11

Going to swap in the old plugs real quick this morning and at least rule that out before calling a roll-back.

UPDATE!

PLUGS!!!!!!!! I swapped back in the old plugs and drove around for awhile with zero issues. Even though the old plugs are virtually annihilated (WAY beyond their life), it runs decent and no misfires or cylinders down.

Needless to say, I'll be returning the "new plugs" to Advance Auto and run down to the dealer to make sure I'm getting the real deal Densos. Should have just done that to begin with.

Guess I'll be doing plugs again tonight. I can do them pretty quick, now! HAHA Hopefully no issues return after I swap them in.

Here's some visuals for you. This is what NGK Iridiums look like when life gets crazy. These things had a great life! I would recommend them for sure!

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And here's some visuals from the Denso's I bought from AA and what the packaging looks like. Sorry I didn't take more pictures of the plugs themselves. I took that one picture before I installed them. I'll try to get some more for comparison sake. I hadn't read about the "FAKE" plugs until this was started, otherwise I would have just gone straight to the dealer. I must have got some junk plugs.

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A question if you do not mind me asking?
Why did you change your timing chain? i'm just curious because according to Toyota, these chains are supposed to be non-maintenance item.
I have a 2004 T4R SR5 4WD with 172 miles, always dealership serviced, and I've read on here a few people change out their timing chains...

Yep! You are generally correct. Should last 300k+, I suppose. However, for some ridiculous reason (as I understand it) there was a quality issue with some of the timing chains on the 4th gen 4.0L's that lead to premature stretch. I made it to 206K before the switch ($$$!!!), but I've heard of people having to do it at 130k. I started getting the codes around 195K. When they changed it they found it had almost 1/2" of stretch. Was pi$$ed that it had to be done, but I didn't have much of an alternative, I guess.

You may have dodged the bullet. Searched the threads here. I think there might have even been a year range.

Okay. I got plugs from the dealer. Same part numbers, but visually they do look a bit different. Very subtle.

FIRST!

The part number for the NGK Iridiums I have been running are as follows:

LFR6AIX-11

This plug cross referenced by the dealer to the same part numbers as the Denso's I purchased:

SK20HR11

These Denso's were apparently only offered on 4.0L V6 in 2009 and are applicable for this vehicle, as were the NGK's listed above. I had them double check everything. These are all "long-life" plugs. 100K plus mileage.

Previous to 2009, only the standard 30K plugs were available, and obviously much cheaper. Praying that the swap goes good and no issues. There shouldn't be, but after fighting with these dang plugs last night, I'm on-edge. HA

Pictures of the dealer purchased Toyota pars for reference. Hopefully this will help someone avoid what I just went through:

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Glad you got it figured out. FYI, it's not really recommended to adjust the gap on iridium plugs due to the brittle nature of the electrodes. However, I've done it plenty of times without issue. Just make sure you are not using the electrode as a fulcrum point when adjusting the gap.

You're right on the year range specific;from the hour i just spend searching the forum, this is more common of 2005-2009 4Runners, specifically on 2007's from what i was reading, how much did you pay to get it done?
glad you found the issue with the spark plugs!

I also did the chain replacement on mine. I dont know if it is a coincidence or a trend but mine is also 2007. So was all other cases that I found on this forum.

Hmmm, it would be nice to do a poll and see how many 2007 4th gen 4Runner owners have change their timing chain. this is really interesting seeing the 2005-2009 are the sought after 4Runner years

UPDATE!!! We have a winner! It runs fantastic on the new plugs and plenty of power to back it up. Feels good to have this "tiny little thing" resolved. Goes to show that buying genuine Toyota parts will just about insure you're installing the right stuff on your 4Runner. Obviously there's some exceptions where you can get away with non-OEM stuff, but with engine stuff, I'll never risk it now.

As for the ECU sounds, I don't think it's related and I haven't heard it again. May be the actuators that some people mention in other threads. Going to keep an ear open and cross that bridge if I come to it.

The quotes all came in around $3500. I had it done at the dealership and I was actually able to get a discount with them because the company I work for has done a lot of business with the owner of that particular dealership, so it was kind of a slam dunk with a heavy discount. When I was first told what it would cost I literally about passed out. I couldn't believe it. But, in retrospect, the vehicle is 12 years old, at this point, and I've had to do very little mechanically to the car, so I guess I was due for a big ticket item. HAHA!

It is very interesting that 2007's seem to have the highest failure rate on those chains. BOOOO!

just FYI, 4.0 V6 is recommended to use OE copper plugs, not platinum or iridium.