lshu

So the last 6 months or so I've noticed that my idle has become pretty rough after like 30 minutes of driving. I usually drive pretty aggresively. Idle when cold is fine. Also, starting out 2 months ago, I've notice that on almost every hard redline shift I get a huuuge pop from the exhaust. I thought it was cool at first (imagine it when I put my mazsport midpipe on), but now it's starting to worry me.

My 8 is an 05 MT with 51K miles, original coils/wires, new OEM spark plugs replaced at 22K.

To complicate things, I've had a small hole in my cat since last year (from hitting a speedbump), from which the car was still running fine (just some exhaust smell). I got a cel right after I got the hole, which was a P420 (catalyst below efficiency threshold).

I've had 1 misfire code about like 6 months ago, but haven't got one since.

From what I've read, I am guessing that it's the ignition coils that need replacing? I asked the service dept at the dealership and he says it could be the leaking exhaust that is throwing off the ECU making the air/fuel mixture too rich. But I haven't had the popping until 2 months ago so shouldn't it have been happening since I got the hole? I believe it's the coils maybe getting weak and not burning off all the gas, causing the popping. Maybe it's a combo of both. What do you guys think?

Juice

iTrader: (1)

Couldn't hurt to replace the coils and plug wires. While your at it, might as well replace the plugs too since they have nearly 30k on them.

As for the hole in the cat, I would take it to a muffler shop and see if they can't weld it shut. Shouldn't take very long or be very expensive.

elysium19

iTrader: (1)

changing the coils is a fine thing to do but to be honest what the dealer/mechanic said is very reasonable. There are 2 O2 sensors in the exhaust system, and (I could be wrong here) but i'm pretty sure they feed back info to adjust the AFR. A hole could definitely screw this up.

nycgps

iTrader: (1)

The Front O2 sensor is the one thats responsible for giving O2 feedback to the system, the 2nd sensor is there to sense cat efficiency.

Buy new coils and wires and plugs. u're set.

oh, u might want to seal that Cat hole up too. not because of the CEL, its because of the carbon monoxide and other harmful gas going into your lungs.

lshu

I just got the coils from the dealer for about $43 each (a little expensive, but I would like to change them this weekend). I'll be also trying to change to the midpipe soon so I'll post again if anything interesting develops.

Charles R. Hill

iTrader: (7)

The coils are probably weak and the popping is due to the hole in the cat-pipe.

lshu

Update:

I just replaced all 4 coils with the updated part ("-100A") this last weekend and it seems to have resolved everything! So far no more rough idling and no huge pops from the exhaust shifting at redline. Even more, I feel the car is revving a TON smoother and has gained like 10 hp that I didn't notice I was missing!! My 8 freakin flies now.

FWIW, my old coils were the un-updated part ("..-100") on my '05 MT, build date 11/04. Each one had heavy white bubbling/burn marks about 1cm in diameter. Not sure exactly when Mazda started using the updated coils, but I would definitely recommend anyone to replace these coils at 51K miles!

nycgps

iTrader: (1)

my build date was about a month later than urs. between then and now, my car has gone thru 5 sets of coils.

the original set, 2nd, and 3rd set was replaced by me. then the 4th set, replaced by dealership for free under warranty about 5 months ago(with plugs), after 5K miles(about a month ago), it gone bad again(with plugs) and replaced again under warranty.

lshu

wow nycgps, what the heck is going on with your ignition?? It seems like something else is wearing out your coils prematurely. There's no way those 5 sets of coils are all defective.

nycgps

iTrader: (1)

orignal set - 1st replacement - misfiring.

1st - 2nd set - replaced cuz I want it to run best

2nd - 3rd set - replaced cuz its misfiring

3rd - 4th set - replaced under warranty cuz its giving out bad sparks.

4th - 5th set - same as above, but this set has only couple thousand miles.

it might have something to do with heat.

lshu

Another update:

The rough idle is back (although it's smoother now with the new coils). Now, I'm noticing power loss after a long drive (>1 hour). I'm hoping that changing out my holey cat will fix it.

lshu

Update:

I got my Mazsport midpipe changed in today. This was the damage on my old cat from hitting a couple of speedbumps. Notice the hole near the front.




Looking into the cat, I found something really shocking:



Where is the catalyst?!!?? You can clearly see the O2 sensor hole on the left. The walls of the chamber are totally smooth with no evidence that the honeycomb material was even there. Surely this can't be normal??

This is the view from the resonator side:



So where did my catalyst go? I guess it has to be in the muffler? So far my car seems to drive fine, but I need to do another >1 hour trip to confirm.

chancejat

iTrader: (2)

thats awesome .....its perfectly clean....you couldnt do better if you gutted it yourself

swoope

iTrader: (5)

i had all the insides of a magnaflow hi flow cat just disappear also... where do it go?

beers

zoom44

notice that your hole was just in the heat shield and not in the cat- unless i'm missing something.

clean your MAF. when cold the PCM is using open loop so its not using the feedback from the sensors. Once it warms up it does. A dirty MAF will cause the poor idle you describe in your situation.

I wonder how long you had a self made mid pipe before you bought your new one?

swoope

iTrader: (5)

nice to see you out!

beers

lshu

My old cat was definitely leaking exhaust (if you look under the car at it you can see the heat waves shooting out). My MAF is clean, I just cleaned it a few weeks ago, so I'm sure it's not that.

I'm pretty sure the catalyst is stuck in the muffler. I drove about 1 hour 30 min today to LAX and I'm getting major power loss after 30 minutes of driving or so. When I floor it, the sound of the exhaust is different than usual, sounds constipated. Not only that, I'm getting a continuous heavy exhaust smell inside the car which get worse when I floor it. I'm not even sure how I get this smell since there shouldn't be any big exhaust leaks anywhere after the installation of the midpipe. Now I'm a bit worried to drive it lest I get carbon monoxide poisoning. Looks like I'll need to examine the muffler.

kersh4w

iTrader: (3)

ahahaha, thats hilarious. i'd take the catless cat to a mazda dealership and demand a replacement.

it looks like it was never installed. hahaha. a brand new cat is worth $1300~, so you could sell it for a bit to a junkyard or keep it if you ever need it.

Rote8

The cat got out through the hole, now you need to change the "litter box"/muffler.

lshu

OK, I changed in my brand new Racing Beat Rev8 Exhaust and have been driving with it for the past week. All seems to be well now, even after a couple of >1 hour trips to UCLA.

Now this is the thing that is really confusing me. I was pretty sure the catalyst had to be stuck in the muffler, as that's the only place it can physically go, but looking in my old muffler, I see this:



No catalyst!! I also shook the muffler and I don't hear anything jingling around. There is no way it went through those perforated holes unless it turned to dust and blew out, or melted and got stuck to the inside of the canister. I also checked the connecting pipe of course, and it's clear. I even tried putting my mouth to the pipe and muffler and blowing, and I THINK it's fine (but I doubt I can blow as hard as the exhaust comes out). Anyways, I don't care too much because my problem seems like it's fixed. The Racing Beat exhaust with the Mazsport midpipe sounds deep and "meaty", I love it! There is a noticeable increase in power too.

lshu

Oh and just in case anyone was interested, here's what my ignition coils looked like after 51K miles (cleaned):

Icemark

Interesting that they were arcing through the bottom on most of them.

Icemark

Not a cat, but a thermal reaction chamber. You can not put a O2 sensor inside the cat.

Why does everyone think that is the cat? Are they confusing it with the FC with it's 2 or three cats?

lshu

I don't think that's true. I've seen pictures of other cat pipes and this is where it is. Where else would the catalyst material be? Any farther upstream is the header going to the engine, and downstream is the connecting pipe and muffler. From what I've read on the forum there is supposed to be a ~3" bank before the sensor hole, and a deeper ~9" bank after the hole.

czar

iTrader: (3)

huu ... that usaly has a the cat right there >_> on a rx8