Walkthru on coil replacement for 2002-

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boldive · Newbie Joined: 22 Mar 2008 Posts: 5

Gasket is made from plastic/rubber material. Don't wary about it. Look at the picture.

alschnertz

milanomike · Newbie Joined: 25 Mar 2008 Posts: 29

Had to do this as I've had 3 coils fail in 2000 miles on my 04 MPV. Great write-up. I'll add that instead of disconnecting the coolant lines from the TB, I simply undid the 4 bolts and let the TB hang. It makes getting the vacuum lines a bit easier. So, I've got six new coils and OEM plugs in my MPV, coil issues should be gone for the next 50 kmiles. Thanks for a great write-up as the Mazda OEM manual isn't the best I've seen.

Mike

saerandy · Full Member Joined: 29 Oct 2003 Posts: 162

Just got to do this wonderful (sarcasm) fix for the third time. Not only that, it was cyl #3 so the fun never stops. When this first happened, it was a front coil. The second time, it was one of the rears, so since I was going to the trouble, I changed all 6 plugs as well as all three rear coils (I still have 2 old coils left in the front). At any rate, 5K-8K miles later the CEL comes on again, and it's a rear coil.

Doing this (rear) the second time around definitely speeds up the job. I also learned from the first time around so if you're going to attempt this for the first time, a "good-to-know" is that you don't need to disconnet the rear PCV valve, nor the two little vacuum lines attached to the TB in the second to last step. By loosening everything else, you can lift and pull out the TB far enough to get to the rear three coils & plugs.

If you are planning on cleaning out the TB, clearly it's easier to pull everything out. But on reassembly, you can attach the PCV hose BEFORE getting the TB back in to place. By far one of the more unpleasant parts of this service is working on the PCV hose back near the firewall. The first time around it made me cuss a blue streak, but this second time it was a breeze.

OK - so the code is clear and since the replacement coils I used the first time around were OEM I actually get a warranty on them. These were the "AC" version, so I just got a bad one. Just my luck.

Now that the misfire code has cleared, I have a new one - P0037. I'm going to clear it & hope it's just a fluke, otherwise I guess I'll be doing an O2 sensor next weekend.

Nick_WI · Newbie Joined: 08 Jun 2008 Posts: 2

Sorry for the noob question, is reading the code with a machine the only way to tell if a coil went bad and which one it is? I don't want to replace any or all if only one is bad. I do not have a way of reading the code myself.

Thanks!
Nick

saerandy · Full Member Joined: 29 Oct 2003 Posts: 162

You are lucky if you have a misfire and the engine stores a code, but it does happen. Autozone will read the codes for free, and you must have at least one near by (or some parts place that would read for free). As you've probably understood from all tese posts, if you have a rear coil go bad (and #3 tends to be particularly suspectable) you might as well change all three in the back as this isn't a job you'll want to do twice. Also, replace all 6 plugs and use a good one like NGK.

The "bad coil behavior" can be caused by coils, plugs, bad pcv hose (very common), gunky throttle body, and sticky or broken IAC valve. Take your pick if you don't have the codes read.

Nick_WI · Newbie Joined: 08 Jun 2008 Posts: 2

Thank you for the reply. Turns out a friend of my wife had what we needed to read the codes:

P0304
P0431
P0306
P0174

He switched coil number 4 with coil number 5, and then I drove it again. We wanted to rule out one particular coil, or at least see if that was the problem. The van ran great until it started raining a little later this evening. Then it was the same story again. He read the codes again and this time it was coil number 6. It seems that I have one or two bad coils.

jaybird722 · Newbie Joined: 07 May 2008 Posts: 25

Nick_WI..

by your codes I would say you have coil #4 (maybe now swapped to 5) and 6 bad.. as well as a vacuum leak...Intake plenum (code 0174).

coils 4,5, and 6 are front and easy to replace...

but it sounds like a full intake remove and clean is in order as well as get some nick NGK's in there while at it..

I have done mine ( when we bought and 3 other friends MPV's) all same proceedure ... as well as then dropped in a nice K/N filter and the improvement is feelable. as well as no more codes lingering..

My 2 cents...

daddyearwig

Man, there's wonderful information in here. Its nice to know there's a place like this. Luckily I'm not in any need for new sparkplugs yet, but the day will come.

This thread just made me chuckle at the amount of work it takes to replace just the sparkplugs...amazing. My first car in high school was a '64 Corvair, way back in 2000.....took 5 minutes to change the plugs (and under $15 for all 6.)

Its just crazy how involved modern cars are. Thanks again for the post, great stuff.

Daniel

kcliss

Question from a noob: how do you reconnect the small vacuum hose on the back of the manifold? It's smaller than the nipple it attaches to, and no amount of working seems to get it on. I've got the coils and plugs replaced, just working on re-assembly.

Excellent walk-through; if I can figure out the hose thing, I'll soon know if I've fixed the hesitation issue.

subearu

One of these hoses? The bottom one is the PCV, the top one is the one I'm thinking you're stuck on.

-Brian

kcliss

The top one is correct. I was advised to just smear some oil on it and work it on, but even if I get it started, it slips back off. I tried using needle-nose pliers, which just resulted in ripping off part of the outer connector.

Hindsight now tells me that actually didn't need to come off, but oh well.

kcliss

Okay, just tried again, and realized I had the wrong end. Jeez. Though I'm not sure where the other end (the end that doesn't attach to the manifold) connects to. And I've torn it all up, too. May have to buy a new one.

Edit: the other end had slipped off, I believe, the EGR valve. It hadn't occurred to me to check, since I'd not disconnected it consciously. Lesson learned, car fixed, beer consumed.

markgrass · Newbie Joined: 09 Jul 2008 Posts: 2

Thanks for the info I'm sure it saved me $$$$. One question, the vacuum from the EGR (I believe- one under the intake manifold on the driver side) got disconnected. I have been trying to find the other end. I am currently getting a p0660 code for open EGR bank 1.
Any help would be appreciated

markgrass · Newbie Joined: 09 Jul 2008 Posts: 2

Again Thanks for all the valuable information the original post has. I actually had two issues. 1. I forgot to plug in the EGR module. 2. During the installation the vacuum hose that goes from below the throttle body was not properly routed and I didn’t remember where it went. After I got my big head and a flashlight into the engine compartment, I was able to see that it went into the smaller hose on the back of intake manifold. Thanks again the information was spot on and valuable.