What kind of performance gain was experienced after swapping all the old plugs? Mine is just over 100k on stock plugs and I don't know if I should do it while I'm changing the belts.
Installed new Plugs and air filter today (1 Viewer)
- Thread starter RobRed
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- Thread starter
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More of a drivability gain. Truck felt better, more responsive.
I just changed plugs on 2003 TLC I just bought at 177K from one owner who had no record of plug replacement. Seven came out easily while one was really, well ....... difficult. The plug was second from front on passenger side, so great access, that was not the problem. While others were easily removed, this one was a rock. I used PBB, was able to get it moving about an 8th of a turn, but then really bound up. I had to make a business trip so soaked it in PBB while gone. Today, after a week sitting and while stone cold I was able to get it moving and out. Plug threads actually looked ok. I got everything cleaned up, used a small amount of high temp never seize on the new plug, truck back together and running well.
Next time, the whole job for all 8 cylinders should take only about an hour and a half, now that I've figured out how to get access. Our shop rate here in North CA is 105-160/Hr, so I think my 1.5 hrs is well worth it.
I was able to find a two volume FSM on ebay and it recommends
Change plugs every 60K (I'm just reporting!)
Torque specs for plugs 13 foot lbs
Next time, the whole job for all 8 cylinders should take only about an hour and a half, now that I've figured out how to get access. Our shop rate here in North CA is 105-160/Hr, so I think my 1.5 hrs is well worth it.
I was able to find a two volume FSM on ebay and it recommends
Change plugs every 60K (I'm just reporting!)
Torque specs for plugs 13 foot lbs
How long should the Denso SK20R11 or NGK IFR6A11 Iridium Plugs last?
The FSM does say 60K miles, Scheduled Maintenance Guide has at 120K miles. Am I reading it wrong?
Parts stores say Iridium last over 100K miles, and some post say 120K.
The FSM does say 60K miles, Scheduled Maintenance Guide has at 120K miles. Am I reading it wrong?
Parts stores say Iridium last over 100K miles, and some post say 120K.
Last edited:
- Thread starter
- #45
Service life CAN be 120k... But degradation happens the first time you start the truck so for me 60k or 4 years.
I'd agree inspect at 60k miles, but why 4 years?
- Thread starter
- #47
Miles are miles but run time (hours) is really what you'd want to measure... I've done so much slow 4x4 work that 4 years is easily 60k miles of run time 
Since mine did not come with records, decided to replace the plugs on my 141K mile 2000 model. Thanks for the post Rob. It went very smoothly. Took about an hour including cleaning all coil packs. I can't believe the dealers charge what they do for this. Picked up the Denso long life iridium SK20R11's at Amazon for $6.03 ea. I removed NGK's so they were likely changed once but it was definitely time for a replacement set.
I just replaced mine today also. 2003 with 163K. It came with pretty comprehensive service records but no mention of plugs so these are probably original. They look pretty good for their age, replaced with the same. It went pretty well, after owning a long series of older BMWs I have a collection of just about every size of extension and flex joint known to man. A couple of them were really tight, and several came out with some very ominous loud squeaking sounds but all is good. Also did the air filter and flushed the PS fluid.
Just did plugs this weekend. Thanks for the walk through and pix. Compared to a couple other plug jobs I've done this one went butter smooth.
2004 LC @ 134k miles, had old NKG plugs that were gapped way off. Installed new Denso SK20R11 ($5.95 per plug off amazon).
I was in need of a spark plug wrench and came across a link to this Gear wrench version somewhere on this site. Bought that for $16 off amazon and it is awesome. Uses a magnet to hold plug in place vs rubber sleeve. Also has a swivel join built into it so it really helped. With the plug tool and 1 joint adapter and one extension I was able to get to all the plugs.
https://www.amazon.com/gp/product/B0014ZVSVK/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
After driving for another tank of gas I did see a slight bump in MPG (about 1 mpg, maybe even a tad more). 1 data point doesn't make a trend but I am hoping the slight improvement in MPG wasn't a fluke.
2004 LC @ 134k miles, had old NKG plugs that were gapped way off. Installed new Denso SK20R11 ($5.95 per plug off amazon).
I was in need of a spark plug wrench and came across a link to this Gear wrench version somewhere on this site. Bought that for $16 off amazon and it is awesome. Uses a magnet to hold plug in place vs rubber sleeve. Also has a swivel join built into it so it really helped. With the plug tool and 1 joint adapter and one extension I was able to get to all the plugs.
https://www.amazon.com/gp/product/B0014ZVSVK/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
After driving for another tank of gas I did see a slight bump in MPG (about 1 mpg, maybe even a tad more). 1 data point doesn't make a trend but I am hoping the slight improvement in MPG wasn't a fluke.
I'm probably one of the least mechanically inclined on this forum and would have never considered tackling this project on my own, however, with RobRed's comprehensive how-to write up including pix and tool list has given me the confidence to at least attempt. I have a 2003 LC with 106k miles, i have been recently experiencing rough idle, and with my local dealer quoting me north of $450 for a spark plug change was just added motivation to do this on my own. Over the weekend i changed the plugs and cleaned the throttle body as well, now she purrs like a kitten, and a qualifiable improvement in acceleration (b/c i dont know how to quantify acceleration). Thank you RobRED for taking the time.
It can be done with care, just don't put pressure on fine wire center electrode or insulator. I'll occasionally find one's where ground wire is out of alignment, that I'll bend. That said FSM is clear: Do not change gap on used spark plugs if out of spec replace. If gap becomes to wide, as they do with age, it pulls to much power and will overheat coil. Heat is the enemy of coils.
