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Guest Message by DevFuse

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98 obw spark plug replacement

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4 replies to this topic

#1 wayneb


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Posted 27 September 2008 - 09:48 PM

Hi All;

Tine to replace plugs and I know I have to use NGK's,learned the hard way!

Does anyone know if platinum or Iridium plugs offer any improvement over stock plugs?

Thanks in advance;


#2 Rooster2


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Posted 27 September 2008 - 10:40 PM

I have a 99 Leggie OBW with the 2.5 motor. I installed Bosch spark plug wires and Bosch Platinum spark plugs. 12,000 miles later, the motor still runs good. I also have a 98 Leggie OBW with the 2.5 motor with OEM type NGK plugs. I can't tell any performance difference between the two engines.

Lots of people have written about trouble with non OEM plug wires and non OEM spark plugs, but I have not had any trouble with Bosch products. BTW, the Bosch wires were about the same price as Subbie OEM wires.

I would suspect buying cheap plug wires and cheap plugs from an auto parts chain is where most people have problems, and develop complaints, and therefore sing the praises about using Subbie OEM parts for the ignition only.

#3 NOMAD327


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Posted 28 September 2008 - 12:51 AM

NGK PFR5B-11 is the original spec NGK double platinum which was standard in the 99 2.5 DOHC engines at least. You can use plugs which are no platinum, or plugs which are double platinum. I would avoid the single platinum plugs because our ignition system will cause two plugs to wear faster than the other two. The plugs are moderately hard to change, and I did not want to do it any sooner than necessary, so I put in the double platinum. The advantage of platinum is they will not wear out as soon. Whatever you use, they will normally not be in stock anywhere you go, (except Subaru dealer), So when they order them for you, they will check what plugs are correct for your engine.
I found the PFR5B-11 NGK at advanced auto for $10 a year or so ago, best price I found back then, as the list on those plugs most places is $15 each and a lot of the internet sources wanted $12 or more with shipping extra. My kid who is on a budget bought Autolite APP3924 for about $4 apiece. They are double platinum and made in America. Very high quality appearance and seemed to match the NGK's for dimensions very well. The car has been running like it should on them for more than 30,000 miles, so they may be OK to use. The plugs on this engine are real difficult to change, so I bought the NGK not wanting to have to redo the job if there were any problems
Some people say there are holes in the wheel openings to make spark plug changing on the DOHC engines easier, but they are not present on my 99. Some people say it's easier to do laying under the car, but it went pretty well on mine from above as follows:
Once you remove the windshield washer bottle and battery (can probably just slide it forward on it’s tray a bit) on the left and the air inlet tube and mass air sensor and air cleaner box on the passenger side, access is fair doing a 2.5 in a 96 to 99 Legacy. I would do the front plug first on each side, as they are slightly easier to do. What makes it the most hard is that the plugs are really far down inside the wells in the heads. The rear plugs on each side are harder because the frame rails are closer in the back. My problem was that an extension was needed, but there isn’t room to get one in with the socket attached. You have to slide the socket into the hole first, then slide in and assemble the extension, and finally attach the ratchet to the end of the extension. I immediately removed the sponge rubber plug protector from my socket, the reason being it will be extremely difficult to get the socket off the end of the plug and out of the hole if the rubber is gripping the spark plug. I didn’t want it on for plug removal either, because there is a lot of trial and error with your socket set as to what gives just the right length for getting the socket stack down into the hole. As I recall, what worked best for me was to use a plug socket in the rear, and then use a ratchet with a standard socket on it to turn the hex on top of the plug socket instead of using an extension. On the front plugs, a 3" extension worked pretty well with the regular spark plug socket and a ratchet. There was at least one plug which worked slightly better with a standard deepwell socket instead of the spark plug socket, but that was not a critical must have item! I would recommend having a small hand mirror on a stick or a ladies compact to be able to glance down into the well to see what’s happening. I’ve done a few of these cars, and on each one, at one time or another, the spark plug socket became slightly jammed on some aluminum protrusions of the head that were down deep in the well. The impression is that the threads are pulling rather than the socket is cocked and dragging. If you experience this, Use the mirror to reconnoiter. If in doubt, reverse direction, and the condition should go away if it’s not the threads. This usually happens when it’s just starting to go real good to scare the heck out of you.
Going back in with new spark plugs, make sure you check the gap first, then lube the threads with an anti-seize compound. Make sure there is a washer on the plug or you will wonder later on if it was in fact there. The big trick for installation, is to have a piece of rubber hose that’s about three or four inches long and a snug fit on the top of the spark plug. Stick it down over the top of the plug and use it to guide the plug into place. Twirl the hose between your fingers and you can probably get the new plug in half to three quarters of the way which ensures the threads are started straight. It's also much quicker and easier than a socket wrench as far as it will go. Putting all the stuff back on after the plugs are in, make sure the three quarter inch hose that connects to the bottom of the intake tract after the air flow sensor is reconnected, The car will not run without the hose connected, and sometimes it slips off unseen during disassembly, and you don’t even realize it needs reconnected.

#4 wayneb


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Posted 28 September 2008 - 12:50 PM

Rooster2: Youv'e had much better luck with Bosch plugs than me! They fouled in my subie within 2k miles.

Nomad327: Thanks for the info about double platinum plugs, didn't know of such a plug. Great description on how to replace plugs! I've found for me that I can replace the passenger side plug easily from below. The driver's side I found through trial and error to do just as you described. One thing I found recently and can't remember where, I bought a long reach plug socket with a swivel end. The socket is about 5 1/2" long and the swivel end is just the right length to attach a ratchet to. Again the rubber tubing works great, learned that trick from working on small block chevy's with headers. Your spark plug replacement should be used as a sticky for others, it's just that good!

Thanks again;


#5 Buick350X


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Posted 28 September 2008 - 08:04 PM

Big vote here for Autolite plats, they last a long time and don't foul.

NGKs suck in my book.

cross reff plus here


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