RX in NC

Changing The 3 Rear Spark Plugs In The Rx300

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To those of you who have been successful in getting to and changing your three rear spark plugs - what tools did you require and what steps did you have to take in order to complete the job? My wife's vehicle is approaching 120,000 miles and I really want to do this job myself if I can manage to figure out a way to get to those very poorly-placed three rear plugs.

I've talked to Lexus mechanics, Toyota mechanics, and independent mechanics about this subject and while they all agree this is a definite pain-in-the-!Removed! job, they all seem to use different approaches. Some recommend removing plenums, manifolds, the windshield rain gutter, etc. Some say they have special tools and socket extensions that allow them to get to the rear plugs without having to remove any other parts at all (but they're reluctant to show me these "special tools", so I question whether it's just another marketing ploy)....

So if you've done this, please list the tools required and the steps you had to take to finally access and change those miserable three rear plugs. As always, thanks for sharing your expertise....

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Hey RX, the job will go easier if you find a 4 inch extension. That is the perfect length. I want to warn you it was no easy task. I remember you are a big man, I hope your hands will work those tight spaces. I do not have small hands but it helps. The other problem I had was the rubber kept coming out of my spark plug socket. I did not have the 4 inch, and had to use a 3 inch with a swivel which kept coming loose. That is the best I can advise you other than you will be working blind to get to them, useing feel. by the way the Iridium plugs where just as cheap at the LExus dealership than online. Good luck friend

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Thanks for the reply, Tom. I'll make sure that I have a 4-inch extension in my toolbox before I start the job.

What components on the vehicle, if any, did you have to remove before you could get to the rear plugs?

In the last couple of days I've found on-line sources for Denso iridium plugs that are about $5 less expensive per plug than what my local Toyota dealership sells them for. The best source so far is through drivewire.com, phone 800-895-8910, priced at $8.76 per plug with no tax and free ground shipping on all orders over $50.

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I removed the plastic cosmetic cover that has the Lexus emblem on it. 2 or 3 allen wrench screws on the front and the thing lifts out. I also removed the Air intake hoses tothe intake manifold to give me some better visual on the driver side of the intake. Be real careful removing the coil plugs on the spark plugs, the plastic gets brittle. Make sure you hand thread the spark plugs with a little never seize on the threads. the extension will help.

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Thanks again, Tom. I'm going to change the plugs at 120,000 miles - the vehicle currently has about 117,500 miles on it so I have some time to get organized and familiar with the task at hand. But I'm certainly not looking forward to it and will allow myself at least a full morning in case I run into major challenges. The good news is that I only have to do this once - the vehicle will be long gone from our garage by the time it needs new plugs again....

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I've changed mine twice...for the back 3 I only removed the pcv and its attached hoses.

For me, the hardest plug was the back right.

I used a short type 1/4 inch socket wrench and had an assortment if extensions to create custom lengths. In one case, the 4" ext didnt clear to where I could turn the socket. The 6" ext was too long. Using various extensions a 5" worked best for me. You migbt prefer something else, so the more varied your extensions the better.

Most important: Take about a foot of hose, push one end onto the tip of a new plug and lower into the hole. Roll the exposed portion of hose clockwise to easily start threading the plug WITHOUT the posibility of cross threading.

Good luck.

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Thanks for the input, guys. I know this task ain't gonna be a walk in the park. It's always good to get advice from those who've already been there.

If my fingers still work after this spark plug change is finished, I'll post my advice on how to best go about accomplishing the job. I'll try to keep my language as clean as possible....

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Changed the spark plugs yesterday. The three front plugs required about 10 minutes total, while the three rear plugs were every bit as difficult to get to and manipulate as everyone says they are. After removing the cruise control assembly and bracket along with the PCV hose, I spent 45 minutes changing the driver's side rear plug and could not manage the center rear plug or the passenger's side rear plug because my hands are simply way too large to get in there and still have room to work with the tools. Enlisted the help of my small mechanic friend in the neighborhood who was a tool-and-die engineer in a GM plant in New Jersey back in the 1970s and 80s. He was able to manipulate the socket wrench and extensions to get the final two rear plugs changed. It took him about an hour to get both old plugs out and then the new plugs in with me serving as spotter, tool boy, and flashlight holder. Glad I'll never have to do this again on this vehicle. By the end of the job, we were both ready to strangle the Japanese engineer who designed the placement of these three rear plugs....

Incidentally, those iridium-tipped plugs are really something. The original factory plugs were NGK, and they still look pretty good after 120,100 miles. The center electrodes were a bit rounded on the edges so the gap had increased slightly, but the plugs were all clean and intact. I believe that I could have easily left them in place for another 30,000 miles or so. I replaced them with the Denso iridium-tipped plugs that I ordered from drivewire.com about a month or so ago for less than $9 each. After about 50 miles of driving on the new plugs, my wife really hasn't noticed any difference in performance. I rarely drive this vehicle so it remains to be seen if I'll notice any difference myself. Any improvement in gas mileage will probably be slight. But new plugs are important for overall health and upkeep, so I'm glad this task is now behind me.

Good luck to all of you tackling this job in the future. For those of you with large hands, make sure you have a small-handed helper close by along with an assortment of socket wrench extensions, especially ones that are 3, 4, and 6 inches. A universal swivel comes in handy, also.

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Changed the spark plugs yesterday. The three front plugs required about 10 minutes total, while the three rear plugs were every bit as difficult to get to and manipulate as everyone says they are. After removing the cruise control assembly and bracket along with the PCV hose, I spent 45 minutes changing the driver's side rear plug and could not manage the center rear plug or the passenger's side rear plug because my hands are simply way too large to get in there and still have room to work with the tools. Enlisted the help of my small mechanic friend in the neighborhood who was a tool-and-die engineer in a GM plant in New Jersey back in the 1970s and 80s. He was able to manipulate the socket wrench and extensions to get the final two rear plugs changed. It took him about an hour to get both old plugs out and then the new plugs in with me serving as spotter, tool boy, and flashlight holder. Glad I'll never have to do this again on this vehicle. By the end of the job, we were both ready to strangle the Japanese engineer who designed the placement of these three rear plugs....

Incidentally, those iridium-tipped plugs are really something. The original factory plugs were NGK, and they still look pretty good after 120,100 miles. The center electrodes were a bit rounded on the edges so the gap had increased slightly, but the plugs were all clean and intact. I believe that I could have easily left them in place for another 30,000 miles or so. I replaced them with the Denso iridium-tipped plugs that I ordered from drivewire.com about a month or so ago for less than $9 each. After about 50 miles of driving on the new plugs, my wife really hasn't noticed any difference in performance. I rarely drive this vehicle so it remains to be seen if I'll notice any difference myself. Any improvement in gas mileage will probably be slight. But new plugs are important for overall health and upkeep, so I'm glad this task is now behind me.

Good luck to all of you tackling this job in the future. For those of you with large hands, make sure you have a small-handed helper close by along with an assortment of socket wrench extensions, especially ones that are 3, 4, and 6 inches. A universal swivel comes in handy, also.

Hey RX sorry, but we warned you, It is nice to have friends that help each other, I do the same for my friends. And your wife is right, no change in engine performance, Mine exhibited no change either, but it is done as you say and not again. Hope things are going well for you, enjoy the fall.

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Yep Tom, you guys did warn me, and I appreciate it. Glad it's done and over with now. Enjoy your autumn as well - gotta love this time of the year....

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Good tips., I replaced the front one without any difficulty in about ten minutes but the three in back was some thing. Poor design by the Lexus engineers. I guess, they do not have to work themselves and expect all consumers like myself and those who do-it-yourself type (us folks) to use dealership for all service needs. I removed PVC and its hose as well as cruise control bracket assembly. I used three inches extension for the driverside and center one. My small hands worked in tight space very well. the one on passenger side was tight to pull as well to insert back in hole. too close to fire wall. I managed to use one three inch extension with a universal and was able to install all three in one and half hour. I used Bosch Platinum 2 Part number #4301 spark plugs instead of the one recommended above..

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Good tips., I replaced the front one without any difficulty in about ten minutes but the three in back was some ting. Poor design by the Lexus engineers. I guess, they do not have to work themselves and expect all consumers like do-it-yourself type (us folks) to use dealership for all service needs. I removed PVC and its hose as well as cruise control bracket assembly. I used two three inched extension for the driverside and center one. My small hands worked in tight space very well. the one on passenger side was tight to pull as well to insert back in hole. too close to fire wall. I managed to use one three inch extension with a universal and was able to install all three in one and half hour. I used Bosch Platinum 2 Part number #4301 spark plugs instead of the one recommended above but continued misfire after 500 miles. Then I replaced NGK iridium plugs as recommended. I have driven for over 2000 miles and no more misfire. 

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Good tips., I replaced the front one without any difficulty in about ten minutes but the three in back was some ting. Poor design by the Lexus engineers. I guess, they do not have to work themselves and expect all consumers like do-it-yourself type (us folks) to use dealership for all service needs. I removed PVC and its hose as well as cruise control bracket assembly. I used two three inched extension for the driverside and center one. My small hands worked in tight space very well. the one on passenger side was tight to pull as well to insert back in hole. too close to fire wall. I managed to use one three inch extension with a universal and was able to install all three in one and half hour. I used Bosch Platinum 2 Part number #4301 spark plugs instead of the one recommended above..

I will say you did a great job, but the Bosch plugs from lots of experience are not good. I would have stuck with the NGK or Denso iridium plugs...Heck they will last 125k miles without even breathing hard. I and many of my fiends, as well as a German Auto garage have found the Bosch plugs fail really early, sometimes within weeks...Sorry friend I do not recommmend them...they have failed in my Honda, Mercedes, and Ford, and my friend at the independent garage says he gets lots of business because of customers whom just changed to them have running and missfire, and he gets the business of finding them and replacing with his choice for the Mercedes and BMW cars. Good luck.

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Tom,

How has your experience with your 2008 RX400h been compared to your old RX300? When did you make the switch, and how many miles were on the 400h when you acquired it?

My wife's 2004 RX330 AWD has been relatively trouble-free so I'm rarely on this forum anymore. Just did the 112,500-mile service last Saturday morning. She is still splitting her driving requirements between her RX330 and our 2005 Jaguar S-Type sedan acquired in December 2008. The S-Type had its quirks but it has been a fantastic car once I worked out those quirks, mostly when the car was still under the original factory warranty. The S-Type is approaching 60,000 miles now and has been trouble-free for the past 18 months or so. It's still the best bang-for-the-buck vehicle I've ever owned in more than 41 years of driving....

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Tom,

How has your experience with your 2008 RX400h been compared to your old RX300? When did you make the switch, and how many miles were on the 400h when you acquired it?

My wife's 2004 RX330 AWD has been relatively trouble-free so I'm rarely on this forum anymore. Just did the 112,500-mile service last Saturday morning. She is still splitting her driving requirements between her RX330 and our 2005 Jaguar S-Type sedan acquired in December 2008. The S-Type had its quirks but it has been a fantastic car once I worked out those quirks, mostly when the car was still under the original factory warranty. The S-Type is approaching 60,000 miles now and has been trouble-free for the past 18 months or so. It's still the best bang-for-the-buck vehicle I've ever owned in more than 41 years of driving....

YOu know, the RX400h is everything nicer....Great road car, drove to Los Angeles twice (435 miles one way) and just felt wonderful...Gets 25 miles per gallon doing this, much better than the RX300...The unknown is reliability of the hybrid hardware...The tranny (CVT) is a breeze, just drain and fill....And the rear transmission is the same...Glad to hear the Jaguar has been kind to you. I was a Sports car nut when younger and drove everything from Austin Healeys, Triumphs, and yes a Jaguar XKE....back then they were a mechanic nightmare...constantly needing attention...The RX400h had 88k miles on it so I will be doing a timing belt etc. but for the price I couldnt loose...got it for half price..of new. Have a great weekend.

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I have a friend that is a Master Toyota tech, he refers to them as "Botched" spark plugs ... :-)

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I have a friend that is a Master Toyota tech, he refers to them as "Botched" spark plugs ... :-)

how appropriate

:whistles:

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Thanks for the post gentlemen...it took me less than 2 hours to remove and replace my plugs. It cost me $12.40 for a 6" extension and 5/8 socket.

Haha....Pepboys quoted at $284 excluding the parts.

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Good job, just takes a little time and a few beers

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These gentleman are telling you the right tools when i did mines i loosed all three plugs and use a fuel or vaccum hose push down on the plug then unloosen them and pull the plugs out hope it helps ?

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I just spent my afternoon pulling the old Iridium plugs and putting in the new Bosch plugs... ...and then I read this forum!

Not looking forward to that job again, possibly in two weeks time. Job would have cost $300 at the Toyota dealership and they probably would install Bosch anyways.

Toyota Harriers 3.0 (a.k.a. Lexus) are popular in Africa imported direct from Japan as they"re RHD. My wife found the Landcruiser GX 4.2D too big so we traded for the Harrier and it's 16 inch pothole hoppers. It sits comfortably on the highway at a 100mph without even trying.

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can I change front plugs for now and change the rear one when I have some time?

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I have changed spark plugs in many cars most are pain in the neck. The best thing I read in this run was the short hose jamed on the tip of the plug once you loosen it, it makes sense it would be easier to turn by hand in a thight place.  If you use a swivel, I wrap them a few times with electrical tape, it makes it rigid instead of wobbly and easier to handle.

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