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About 2,000 miles ago I replaced my spark plugs with Bosch Fusion plugs. You know, the ones with 4 tips on them. Cost me $10 each. About 300-400 miles ago I got a after driving 50 miles or so after getting some gas (not a full tank). I drove about 150 miles with it before I could get the code read at Autozone. But before I got to Autozone I filled up with gas again, this time all the way full. When I turned the car back on the CEL went away. I went to Autozone anyways and they were able to pull the code. The code read: Multiple Random Misfires. I'd been noticing something that felt like that while cruising. A slight hesitation almost not noticeable. The code still hasn't come back in but I wanted to go to the dealership to see what they would say. When I was describing the problem the service rep said that it was because I was using Bosch plugs and that the only plugs that ANY Japanese built car could use were NGK plugs, also at $10 each (never heard of them before). Does this sound right or is the dealership trying to make a quick buck? I don't think my plugs are the problem I've always used Bosch products (including plugs) and NEVER had any problem with them at all. I pulled the plugs and they all looked just fine. All the wires are on tight and I don't hear any misfires. The car starts like new every time. I did have a problem at about 4500 miles with my fuel pump but the dealership said it was a known issue on some 3's and they fixed it under warranty. Could that be the problem? How bout a dirty fuel injector? I'm not sure what else to check. I just don't want to go into the dealership and they tell me it was the plugs and that not be the real problem. Suggestions?
 

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The dealer is right about Mazda3s using NGKs.

Because they are unfamiliar with other plugs, they have to assume it's the plug that's causing the problems.

I think NGK Iridiums are only like $7ea...

The gap has to be set correctly, the torque, and the right plug has to be used if you go with another brand.
 

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Discussion Starter #4
I thought about it being a bad tank of gas also but I've filled up again since then and the problem hasn't gone away. Just the CEL hasn't come back in. I still feel the misfires when I'm driving.
 

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haha, those Bosch Fusion 4-prong plugs are such a gimmick, i feel sorry for you since i used to fall for stuff like the "split fire" and other shit.

NGK Iridiums came on the car, they are great plugs, better than everything except for Denso's

if you wanna change plugs go with the NGK's or if you want to "Upgrade", go with the DENSO Iridiums.

Nothing Else, Period.
 

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Dunno how relevant this is, but I put bosch fusion spark plugs in a '91 accord and it worked just fine.

but that was just a week or so before i flipped it so i dunno how it woulda worked long-term.
 

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[quote author=ViperDom link=topic=70030.msg1220784#msg1220784 date=1172068414]
haha, those Bosch Fusion 4-prong plugs are such a gimmick, i feel sorry for you since i used to fall for stuff like the "split fire" and other shit.

NGK Iridiums came on the car, they are great plugs, better than everything except for Denso's

if you wanna change plugs go with the NGK's or if you want to "Upgrade", go with the DENSO Iridiums.

Nothing Else, Period.
[/quote]

+1
 

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Plugs can be a finicky thing. Try the NGKs.

How many miles did you get out of the original plugs?
 

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The Bosch plugs are a gimmic, electricity will follow the path of least resistance so the "multi-tip" plugs are pretty much worthless. Also look at it like this...If you are trying to start a fire, would you like one large spark or three little weaker ones?
Put the NGK's back in and you should be fine.
 

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Dang $10 for the NGK's that's a heck of a deal. I believe I paid $71 out the door for my 4 plugs from Jim Ellis Mazda. Non of the parts store had these plugs in stock...and when I had them try and order them after a week went by they finally told me ohhh they are telling us they are on backorder. I changed mine when the car had approx. 37k miles...I don't trust or buy the 75k intervals...JMO.

+1 for whoever mentioned NGK and Denso as being the best plugs.
 

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Discussion Starter #11
I guess I'll be changing my plugs back. Unfortunately when I first put in the Bosch plugs the car ran just fine. Almost better than before (although that was probably psychological.) So I dumped the stock plugs. Figures that I'd need them later on huh? Just curious though... why did the car run just fine with the Bosch plugs for about 1500 miles before I got any problems? And is there a certain torque spec I should put the new NGK plugs in at? BTW, I changed the plugs after about 33,000 miles.
 

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Both the NGK Ir's and Denso Ir's have tapered seats with no washer. they dont need much torque. All you need to do is tighten Firm with you fingers. then put your ratchetwrench on and turn another 1/16 of a turn.
Basicaly picture a Clock looking down at the ratchet and turn it 1hour, or 4 minutes
Look at this picture for the "Taper Seat Plug"
http://www.densoiridium.com/installationguide.php

Spec from NGK
7.2~14.5 ft/lbs
Spec from Denso
7~15 ft/lbs

(a torque wrench is unnecessary. since your cheepo torque wrench isnt good at reading down below 20 ft/lbs)

The NGKs are 7-8bucks in stock at PepBoys/Autozone
The Densos are 12-13bucks @Autozone (they'll prob have to order them, but it only takes a day or 2)

Goodluck, and dont forget to throw some Dielectric Grease on the top of the plug:
http://www.idealtruevalue.com/servlet/the-74255/Detail
and a little Antiseize on the threads of the plug (only a little)
both sell at any auto store for a buck or 2
 

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Just another confirmation on the "random misfire" CEL when using the Bosch Fusion plugs. The condition showed up in less than 50 miles of driving. Resetting the ECU and re-installing the old plugs fixed the problem. When I returned the plugs to the retailer, he confirmed that this is a common complaint in "direct fire" (coil on plug) cars. By the way, the "old" plugs had/have 62,500 miles and still look great - the 75,000 mile change interval is quite realistic and possible because the ground electrode (which normally wears faster than the center electrode) has a 1mm platinum disc welded on directly across from the iridium tip. Here are the correct Mazda 3 numbers from NGK:

Standard iridium plug - TR6IX - about $5.50 locally - standard ground electrode.
OEM iridium plug - ITR6F13 - about $12.00 locally - platinum tipped ground electrode.

Some cars, mine included, shipped with an ITR5F13 (OE plug for the 6), which is one heat range higher. I'm not sure why Mazda would spec a different plug for the 6 as the MZR engine used in both cars is essentially identical. IMO it's best to stick with the OE part number as it's something most owners will only do once - it only costs about 10 bucks more than a tank of gas around here...
 

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Yup, lots of guys with 3's have issues with eh Bosch 4 tip plugs. My friend has a GTI VR6 Turbo, and right now is running them, and he's misfiring like no tomorrow. I fully expect some quality plugs to fix it all.
 

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I put in the Bosch +4 plugs in my 04 2.3L and was having the same sluggish/misfire performance so after reading on here about the NGK V and Denso's I went to autozone to try and get them, well low and behold they did not have them in stock and the computer said it is not an orderable item. Guess I am stuck ordering them online.
 

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[quote author=rpn453 link=topic=70030.msg1221811#msg1221811 date=1172091126]
Plugs can be a finicky thing. Try the NGKs.
[/quote]

++

I've had some engines that run fine no matter what plugs I put in them and others that like one type of plug and nothing else. Sometimes you just have to go with what works rather than the brand you prefer. It shouldn't be that way but that's the way it is.
 

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Well, here's a new angle on this. My car was slightly misfiring BEFORE I put the Bosch plugs in, which is what motivated me to replace them in the first place. It was great (better than new, no really) for a day, but the day after the misfiring was back. Anyone have a part number on the NGKs?
 

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[quote author=MCRacing524 link=topic=70030.msg1223622#msg1223622 date=1172154263]
Dang $10 for the NGK's that's a heck of a deal. I believe I paid $71 out the door for my 4 plugs from Jim Ellis Mazda. Non of the parts store had these plugs in stock...and when I had them try and order them after a week went by they finally told me ohhh they are telling us they are on backorder. I changed mine when the car had approx. 37k miles...I don't trust or buy the 75k intervals...JMO.

+1 for whoever mentioned NGK and Denso as being the best plugs.
[/quote]


NAPA carries NGK. (I think they carry Nippon Denso also, IIRC)


My Honda previously, didn't like Bosch, either. I've been using NGK for the past ~10 years.

I just changed out my plugs on the Mazda at ~65k. Plenty of electrode left. No fouling. BTW, my Honda had over 100k miles before the plugs were changed. 125k miles before the stock clutch was replaced.


ViperKiller, look about four posts up. edbuckles posted the part numbers.

Standard iridium plug - TR6IX - about $5.50 locally - standard ground electrode.
OEM iridium plug - ITR6F13 - about $12.00 locally - platinum tipped ground electrode.
 

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NGK and Denso are normally about the same price.

NGK are easier to find so I would stick with those, Denso are not anything special and are pretty equal to NGK.


NGK FTMFW
 

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[quote author=ADaughen link=topic=70030.msg2442395#msg2442395 date=1215367528]
[quote author=MCRacing524 link=topic=70030.msg1223622#msg1223622 date=1172154263]
Dang $10 for the NGK's that's a heck of a deal. I believe I paid $71 out the door for my 4 plugs from Jim Ellis Mazda. Non of the parts store had these plugs in stock...and when I had them try and order them after a week went by they finally told me ohhh they are telling us they are on backorder. I changed mine when the car had approx. 37k miles...I don't trust or buy the 75k intervals...JMO.

+1 for whoever mentioned NGK and Denso as being the best plugs.
[/quote]


NAPA carries NGK. (I think they carry Nippon Denso also, IIRC)


My Honda previously, didn't like Bosch, either. I've been using NGK for the past ~10 years.

I just changed out my plugs on the Mazda at ~65k. Plenty of electrode left. No fouling. BTW, my Honda had over 100k miles before the plugs were changed. 125k miles before the stock clutch was replaced.


ViperKiller, look about four posts up. edbuckles posted the part numbers.

Standard iridium plug - TR6IX - about $5.50 locally - standard ground electrode.
OEM iridium plug - ITR6F13 - about $12.00 locally - platinum tipped ground electrode.
[/quote]

Actually, I saw those after I made the first post so I tried to search for them. It appears those aren't the right numbers or at least the OEM part numbers are different than what you get at Autozone. I found some at O'Reilly's but they were a different number as well.
 
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