Hello and Question about my 2008 FJC (1 Viewer)

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Hi All,

My driveway was recently graced by a 2008 AT 4WD FJ Cruiser with over 230k on the odometer. While diagnosing a catalytic converter malfunction, I noticed that the driver's side bank had NGK plugs installed, but the passenger side bank was equipped with Denso plugs. My understanding is that many FJCs rolled off the assembly line this way, so I can only assume the previous owners never replaced the spark plugs.

I would estimate the spark gap on those plugs to have been 0.15" when I pulled them from the engine. I replaced them with Denso copper plugs. On the bright side, the new plugs seem to have cleared the catalytic converter codes.

My question is this:

Should I replace all of the coil packs due to the extended interval that the engine ran with spark plugs gapped greater than spec? The extremely high resistance of such a big air gap suggests that the coil packs pushed more voltage than normal in order to generate spark, putting unusual thermal stress on the ignition system. The previous owner said that he had replaced the battery and alternator a couple of years ago, and that makes me think the electrical system really suffered due to the lack of spark plug maintenance. The idle has an intermittent miss, but I can't identify which cylinder is the culprit. I ordered six Denso coil packs today, but I'm not sure if I should replace them all and sleep easy, or if I should try to diagnose the original coil packs, replace only the bad ones, and return the extras.

This is my first Toyota, so any advice/suggestions are welcome and appreciated.
 

BMThiker

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I have had a few fail, but just drive it until you get a failure. They have specific codes for each cylinder so they are easy to diagnose quickly.
 
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I'm trying to recall when (since 1975) I've ever replaced a plug until 100,000. Yeah, one Ford Hybrid had plugs that should have been replaced at 100: but at 200k it was still running - just throwing a 'possible' plug issue that turned out to be an air sensor. Yes, the plug tip was a bit rounded - but gap was still within tolerance.
 

TrickyT

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2007 - 2009 FJCs used 30,000 mile copper core plugs. 2010 - 2014 100,000 mile iridium plugs. Different 4.0 V - 6 engines.
The engines are very similar. Variable valve timing on the intake valves was added in 2010 and air pump injection into the exhaust manifold was added in 2013, as were tweaks to the catalytic converter and on how the fuel pump is controlled. The factory recommended replacement interval on the iridium plugs is 120K. All of these changes were aimed at improving emissions. In the end, the never ending regulatory pressure on improving fleet fuel economy and emissions was a major factor in Toyota deciding to discontinue sales of the FJC in North America in 2015.
 
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I also think you are over-analyzing it. The coil packs are probably just fine. Sucks they are original plugs, but from that lack of maintenance, you'd be better off putting the money in the rest of the items that probably never got touched if you have not yet.

Each and every fluid, belt, maybe the PCV valve (which is easy to do when doing plugs since its right above the last driver-side one)
 

fjc-man

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The engines are very similar. Variable valve timing on the intake valves was added in 2010 and air pump injection into the exhaust manifold was added in 2013, as were tweaks to the catalytic converter and on how the fuel pump is controlled. The factory recommended replacement interval on the iridium plugs is 120K. All of these changes were aimed at improving emissions. In the end, the never ending regulatory pressure on improving fleet fuel economy and emissions was a major factor in Toyota deciding to discontinue sales of the FJC in North America in 2015.
Tom, the FJCs always had VVT. Starting in 2010 they had rocker arms and hydraulic lifters and cartridge style oil filter above the skid plate.
 

TrickyT

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Yes, dual VVTi is what I meant. Thanks for clarifying. All in all, the V6’s in all years of the FJC in North America were very similar and shared with several other Toyota’s vehicles like the Tacoma.
 
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Joined
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Hey folks,

Thanks for the input. Here is an update for anyone in a similar situation who looks at this thread in the future.

20200912_233716.jpg


I overestimated the gap in my previous post, it's closer to 0.1". Still huge compared to spec.

I ended up replacing the six coil packs using Denso 6731308, for about $32 each from RockAuto. I would have tested the original coil packs if I had an oscilloscope or one of those fancy spark analyzer tools.

The four-pin coil packs have one wire (IGf) for ignition feedback to PCM, another (IGt) for the trigger signal from PCM, and the other two are switched +12V and ground.

I also think you are over-analyzing it. The coil packs are probably just fine. Sucks they are original plugs, but from that lack of maintenance, you'd be better off putting the money in the rest of the items that probably never got touched if you have not yet.

Each and every fluid, belt, maybe the PCV valve (which is easy to do when doing plugs since its right above the last driver-side one)

This is good advice. Rear diff oil was fine when I replaced it, brake pads and rotors still have lots of life left, serpentine belt is new(ish), alternator has been replaced, thermostat too, etc, so I think the previous owner thought the plugs were platinum/iridium and also forgot to change them at 120k. My most pressing concern is to examine everything that the lack of good spark may have damaged, starting with upstream O2 sensors. I forgot to mention in the initial post that I have the four lights of death, which is part of the reason that I want to be thorough with bringing this motor back to good shape; I'm not just randomly replacing parts. The fact that the alternator had to be replaced tells me that excessive spark gap/resistance really stressed the electrical system in the vehicle.

For posterity's sake, here is some material that I found informative: This is an old but enlightening Toyota document that covers some of the functionality of Toyota ignition systems. This diagnostic video goes into some detail about how COPs function, and this one explains how the PCM triggers the COP.
 

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