Changing spark plugs in 2005 Tundra V8...advice needed

[sixdogs]

The plug change was easy yesterday and yeah, I did over engineer things. But I had never changed plugs in anything with aluminum heads and didn't want to screw it up. Anyway, the old plugs came right out and the new ones went right back in. I torqued accordingly but the simple extra twist after the crush washer contacted the head would have worked fine. In any event, it's done.

The old plugs were laser iridium with 96,000 miles and looked worn. The gap had opened considerably on some of them and there was some metal deposit on the ground wire portion of the plug. Heat and combustion looked as they should. Now lets see if the mileage improves since it had dropped off recently.


I have a follow up question. On the IR plug box there was a noticeable warning not to re-use the crush washers. That's a given. But does this also mean you cannot remove and reinstall an IR plug in the same hole or do you need to use a new washer/plug? Stupid question but would that apply to checking the plugs in any aluminum head engine or is this just the typical warning that's been on plug boxes forever or a special warning for aluminum heads? Can you remove and reinstall the same plugs in an aluminum head?

 

[aczlan]

They also recommend changing wiring at that time, but I've had others say that since the wiring is low voltage with the coil on plug design, it doesn't matter. Any experience on that?

Not needed with a coil on plug system IMO.

I have a follow up question. On the IR plug box there was a noticeable warning not to re-use the crush washers. That's a given. But does this also mean you cannot remove and reinstall an IR plug in the same hole or do you need to use a new washer/plug? Stupid question but would that apply to checking the plugs in any aluminum head engine or is this just the typical warning that's been on plug boxes forever or a special warning for aluminum heads? Can you remove and reinstall the same plugs in an aluminum head?

Theoretically, you nshould replace it every time. The crush washer is made of a soft metal (usually Aluminum or Copper) and deforms to fill in the imperfections on both mating surfaces making a (almost) perfect seal.

Aaron Z

 

[dfkrug]

Stupid question but would that apply to checking the plugs in any aluminum head engine or is
this just the typical warning that's been on plug boxes forever or a special warning for aluminum heads? Can you remove
and reinstall the same plugs in an aluminum head?

That's the generic warning. I do not know anyone who buys new crush washers when replacing a used plug.
I have replaced plugs on hundreds of different engines, 99% with aluminum heads. It is often a good idea to
look at your plugs now and then to get an easy state-of-health check on any engine. I use a bit of 50-90wt
oil on threads as my "anti-sieze", and tightening a used plug will feel a lot different than one with a new
crush washer.

Interesting that the Toyota had eroded the Iridium plugs....mine still look great at 90+K miles.

 

[sixdogs]

Well, it certainly widened the gap but there was also a metal deposit/transfer as well to the ground side electrode. Beats me but my mileage appears to be better. Truck idles smoother too.

 

[sixdogs]

Update a month later. My mileage is up by at least one MPG and the idle is noticeably smoother. Actually, I figured the mileage would have been up more considering nearly 100,000 on the old plugs. Plug technology sure must have improved the last number of years.

I'll know more on the mileage when the weather warms up.

 

[3930dave]

1 mpg up is pretty good, this time of year.

Not saying Toyotas, but it's not uncommon to have a coil go out on coil-on-plug engines. Since even a 4 banger can keep going on 3 cylinders, there's probably a bit of cost-optimization going on - compared to single coil engines.

That said, IMO, one thing that may be helping these small COP coils along to an early grave is leaving these modern high-tech plugs in for a ton of miles. Modern plug gaps are wide, so these coils work hard from mile 1. As good as these modern plugs are, they will erode a bit during their rated life - so by end-of-rated-life of these plugs, these COP coils are working pretty hard.

100,000 is a lot of miles, but some people just keep on rolling past that.....

Rgds, D.

 

[meos1]

.



I changed the plugs on my E150 300-6 at ~95K. It was running fine but I just couldn't stand having plugs that old. The electrodes were worn badly but again, running fine. ???

I've found over the years that never seize dries out with time. So I've been using moly wheel bearing grease for many years now. Plugs, brakes, every bolt I R/R. Even on hot components it's still there and wet at the next disassembly.

When I was younger I used to put a drop of oil from the dipstick on the new plug threads. But that was back in the days of annual tune-ups. Worked for that interval.

I won't put any bolt back dry nowadays. Well, head bolts, but that's it.



.

I thought the new ARP guidance speced out a lube to ensure good stretch? Im not a pro so I could be wrong.

 

[BobRip]

1 mpg up is pretty good, this time of year.

Not saying Toyotas, but it's not uncommon to have a coil go out on coil-on-plug engines. Since even a 4 banger can keep going on 3 cylinders, there's probably a bit of cost-optimization going on - compared to single coil engines.

That said, IMO, one thing that may be helping these small COP coils along to an early grave is leaving these modern high-tech plugs in for a ton of miles. Modern plug gaps are wide, so these coils work hard from mile 1. As good as these modern plugs are, they will erode a bit during their rated life - so by end-of-rated-life of these plugs, these COP coils are working pretty hard.

100,000 is a lot of miles, but some people just keep on rolling past that.....

Rgds, D.

Yep! The wider the gap, the more voltage it takes to jump it. This high voltage then breaks down the coil insulation. I had not considered this before, but it makes a lot of sense.

 

[sixdogs]

Yep! The wider the gap, the more voltage it takes to jump it. This high voltage then breaks down the coil insulation. I had not considered this before, but it makes a lot of sense.

So to fix this you just replace the coils?

 

[3930dave]

So to fix this you just replace the coils?

If your engine is running smooth, with good power, no foul incurred. Many modern engine computers are able to catch an occasional misfire on an individual cylinder - sometimes this can be nothing more than bad fuel though. If a set of plugs doesn't fix a persistent misfire, then the relevant COP coil may be ailing. Changing one is normally easy; changing many gets expensive.

Not trying to raise any false alarms sixdogs.... if your gas mileage is good, engine smooth, and no engine codes lit up on the dash, then all your COP coils are likely fine.

My comment (re. your timely maintenance) came from seeing various vehicles rolling through my buddy's shop.... one Civic long overdue for plugs needed 3 coils replaced.

Rgds, D.