I was just about to post this too. It’s easy to make incorrect assumptions since the 4th Gens have quirks like this, another example being that 4th Gens use ATF as power steering fluid. I had never heard of that before buying this truck.

I kept my original timing chain when I did my HG at 160k miles. Not stretch or wear at all. 2005 v6.

Adjusting the gap on Iridium plugs is a no-no, and may have been the cause of your issue. I use Iridiums where they are specified and always stick to OEM (Motorcraft for our Mercury, GM for the Chevy). For my '07 4Runner (stretched timing chain replaced at 164K miles BTW) I stick with copper Denso plugs. First set was from Advance Auto, ran them ~40K miles with no issues. Second set was Toyota/Denso from the dealership as they had a parts coupon that made 'em cheaper than AA or Amazon.

Never gap iridium plugs. Risk breaking the tips is not worth their high efficiency even if gap is a little off.

I'm starting to see an 07 timing chain trend.. maybe a bad batch of timing chains

New plugs ran great on my more than 20 hours of total highway drive time through the mountains and hard driving, over the weekend.

According to the dealer, that is a correct statement, up until 2009 when they were offered as standard for the 4.0 V6. Same engine. They were simply not available as OE before 2009 for that particular engine and that's why the recommendation as a cross-reference to anything before 2009 doesn't recommend a Platinum or Iridium.

Just passing on what the dealer told me when I purchased these plugs.

In my vehicle's case, the original owner was negligent on oil changes which likely contributed to the chain failure. He was running 20-30K miles on crap oil.

With that said, I've seen pictures of '04-05 engines with major sludge (mine was fairly minor) and the chain tensioner showing no/minor chain stretch.

yikes!

Lets stay on this nerve for a minute. What are the definitive symptoms of a "stretched" timing chain? If that is even a good term at all... I'll withhold comment until someone with better measurements and data speaks up. I'm at 192K

thx

I can't speak for everyone else, but for me it was throwing codes pointing at VVT and my fingers were crossed that it was the oil control valves. Literally was about to order them and do them. I started a thread here and several people immediate spoke up and said that there was a strong possibility it could be the timing chain (which blew my mind). I was out of time to do the repair (needed to pass smog, so action had to be taken), so I took it in and they confirmed pretty quickly that the timing was off quite a bit and what the next step would be. For me it was worth taking it in to make sure that's what it was so eating the diagnosis costs would have been worth it before going any further ($120 max charge) only to find out it wasn't the OCV's, which it wasn't.

Physically, it was a bit down on power, gas mileage was starting to suffer, and it idled sort of odd. All of this could have been related to my old plugs, also, but it did have a noticeable change in power and gas mileage after the timing chain was changed and further improvement with the new plugs (obviously).

There are some Youtube videos on diagnosing the problem yourself if you have the equipment, otherwise a reputable mechanic can diagnosis it without pulling the engine apart. Dealer should be able to perform this service for you also, if you choose to go that direction.

Here's the thread I started about the OCV's that turned into "check your timing chain"
4.0L V6 VVT Oil Control Valves

Check Engine light and P0016 error code seems to be the usual first indication of timing chain elongation.

Easily confirmed by removing the small square 4-bolt cover plate on the front of the timing cover and examining the chain tensioner plunger extended length.