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DIY: IS350 Spark Plug Service

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Old Aug 24, 2010 | 09:16 PM
  #46  
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Originally Posted by lobuxracer
There's a plug torque spec for a reason. If you overtighten, the shell distorts, the center electrode isn't where it's supposed to be, and it affects heat range - typically making the plug run hotter.

Use your torque wrench. There is no better way.
Should it be oiled then?
But at 14-18ft lbs a small percentage of error from the oil isn't going to be a big deal.
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Old Aug 24, 2010 | 10:27 PM
  #47  
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The FSM doesn't say 14 - 18, it says 25 N-m or 18 ft-lb. They're not offering a range of torque, they never do. They also don't say anything about oil, anti-seize, or any other kind of thread preparation. They expect the plugs to be installed dry.

If you change plugs frequently, anti-seize will help you keep the aluminum in the threads and not pull some out with every plug change. This was a very big deal when I worked on air-cooled motorcycles because plugs didn't last all that long in them. It's not such a big deal when the recommended service interval is 60k miles.

FYI - for all the junior tuners out there - you can't tell jack about what kind of service life is left in a plug by looking at it. A bad plug can look perfectly normal and be worthless in service. There are machines which are capable of testing a plug under service conditions by applying pressure to the area where the gap is and measuring the voltage required to strike an arc. If you don't have access to tooling like this, you'll need to decide when to change based on either the factory's recommendation (required to meet emissions standards) or by keeping track of your gas mileage sufficiently to know when your engine is running significantly worse (with seasonal adjustment).

I chose the factory interval only because it's easy and its guaranteed to work. Some people use this same approach to oil and filter changes, others don't. If I had the machine to test the plugs, I'd probably test them and find out if they still have some life left in them by comparing them to new. Since I don't and I really don't envision buying this machine to be cost effective even over the long haul, I'll stick with the factory interval.
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Old Aug 25, 2010 | 11:14 AM
  #48  
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Originally Posted by lobuxracer
FYI - for all the junior tuners out there - you can't tell jack about what kind of service life is left in a plug by looking at it. A bad plug can look perfectly normal and be worthless in service. There are machines which are capable of testing a plug under service conditions by applying pressure to the area where the gap is and measuring the voltage required to strike an arc. If you don't have access to tooling like this, you'll need to decide when to change based on either the factory's recommendation (required to meet emissions standards) or by keeping track of your gas mileage sufficiently to know when your engine is running significantly worse (with seasonal adjustment).
And for all the not even junior electrical engineers out there, the physics of di-electric breakdown is well understood and you don't need to have a fuel injected pressure chamber and variable voltage coil to tell if your plugs are done or not. Fuel economy will be sufficient to tell if you get a lot of misfire or not.

BTW, no matter how well tune is your engine, they all misfire once in a while and it is how often they misfire that matters. Also depends on how you drive you car your plug can last more or less than the factory recommendation interval. Maybe Toyota tested with the worst case scenario (people driving like a maniac for 60k) and you don't drive like that, therefore making the plugs last longer than 60k.

I'm not saying that everyone should extend their plug life to 90k, but I'm saying that 60k seems VERY CONSERVATIVE and I probably will pull the plugs out to see if they are done for at that time. Pulling them out every 30-60k does reduce the chances of seized plugs and it's worth doing even if you are not replacing the plugs.
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Old Aug 25, 2010 | 03:11 PM
  #49  
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I may have looked over this, but is this the same for the 2006 GS300 AWD, thanks
Can't find anyone with the spark plugs
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Old Aug 25, 2010 | 06:31 PM
  #50  
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thx.. this will come handy.
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Old Sep 2, 2010 | 05:05 AM
  #51  
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Is there a cross reference part number say for example if I go to a toyota dealership?
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Old Sep 14, 2010 | 02:31 PM
  #52  
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Good advice Lobux...I have not experienced misfiring and such, but really would not know much to recognize it anyways. Sewell Lexus has the plugs online for sale and I just assume change them around 60K anyways and not worry for several more years. Not too expensive anyways and local mechanic will install them for $40. Peace of mind.
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Old Oct 10, 2010 | 08:33 PM
  #53  
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Just did it this weekend. 5 of the 6 were super simple, did that in about 90 minutes and i was moving slow, wiping things down as I went along.

The screw on the drivers side, furthest from the firewall is a *****. This screw seemed tighter than all the rest and I ended up rounding the only 2 accessible sides (the screw is in a real crappy spot). So the only way I could get it out was to loosen up the manifold, rock it up a small amount and at that poin I could get my smallest socket in place. That part took me several hours and a few trips to the store to try to find a better tool.

My tip - take your time and make sure you have the wrench fully on the screw head. It doesn't take much to round it out. I'm generally pretty good with these things so I was surprised I had so much trouble.
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Old Dec 19, 2010 | 04:18 PM
  #54  
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The last screw thrizzy is talking about can be taken out with time and care with a combination wrench. Loosen the wire harness nuts and bolts. Lift the wire harness out of the way as much as you can. Then use the combo wrench 1/8 of a turn at a time (thats about all you can do because of restrictions) to get it loose. Then use your fingers when it is loose enough. If you ever think you will change your spark plugs again put anti-seize on it!!!
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Old Dec 19, 2010 | 04:32 PM
  #55  
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geez this looks alot easier then my flippen 250 =/ FML took me forever! but the dealership wanted $500. tomorrow ill do the cabin filter =) good DIY though!
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Old Dec 26, 2010 | 04:00 PM
  #56  
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Originally Posted by isthrizzy
The screw on the drivers side, furthest from the firewall is a *****. This screw seemed tighter than all the rest and I ended up rounding the only 2 accessible sides (the screw is in a real crappy spot). So the only way I could get it out was to loosen up the manifold, rock it up a small amount and at that poin I could get my smallest socket in place. That part took me several hours and a few trips to the store to try to find a better tool.

My tip - take your time and make sure you have the wrench fully on the screw head. It doesn't take much to round it out. I'm generally pretty good with these things so I was surprised I had so much trouble.
I ran into the same issue today. I was able to get an open-ended 10mm wrench on it, but not able to get enough torque to break it loose.

Someone earlier mentioned that they were able to get a 3/8" socket on it, but no way that was going to happen on my engine. I'm going to have to make a trip to the store to find a small 10mm joint-type socket that will give me the angle i need.
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Old Jan 7, 2011 | 06:10 PM
  #57  
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Awesome DIY. I was worried I'd have to take off the intake manifold. You saved be both grief and $300 taking it to the dealer!
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Old Jan 7, 2011 | 06:27 PM
  #58  
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Nice documentation...Can you post a reply with pics 3 and 15? 3 being the new plug and 15 being the 60K plug?
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Old Jan 9, 2011 | 11:38 AM
  #59  
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Quick and stupid question - the Spark Plug Socket, is that a particular size (15mm, etc) or is there a standard size for those?
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Old Jan 10, 2011 | 06:13 AM
  #60  
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5/8" with rubber gasket worked for me
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