Rough running, flashing CEL, glowing cat converter
 

Friday night I started the car and it almost immediately started running rough. Lots of vibration. I started to back it out of the garage and noticed the CEL was flashing. It then smoothed out for a little while and then started running rough again. I sat in the driveway and it repeated this cycle about three times total before I said to myself "this isn't a glitch" and pulled it back in. Total time, maybe 2-3 minutes. Back in the garage I noticed a hot, mild rotten egg smell. Something told me to look under the car and the cat had a slight red glow. (Thankfully it was dark, otherwise I wouldn't have noticed this).

Needless to say, I'm nervous about driving it right now. The nearest Mazda dealership is about an hour away. I have some theories as to what might be wrong, but I am interested in what you guys think.

The car is a 2004, manual transmission, bought used in Feb. with 49K on it, car has ~56K on it right now. Car is stock, no engine related issues with it up to this point. Other than oil changes and a K&N drop in filter, I haven't touched the motor. I drove the car to work on Thursday and it ran without a hitch. I didn't drive it on Friday until that night.

Any and all help is appreciated!

Luke

Welcome to the world of a clogged cat! Get it replaced, good to go.

You may want to look into maybe if the cat failed prematurely. If you have bad coils/plugs/wires, it could cause/speed up this issue. Do you know when those were replaced?

Yeah man, get it replaced...the dealership will do it for FREE. Federal emissions standards covers it up to 80k.

Thanks!

I had similar suspicions. My question is would the symptoms of a clogged cat appear so suddenly? The car seemed fine the rest of the week and runs (well, ran) strong.

The previous owner said the plugs had been replaced, but I don't have any record of that in the maint. info. he gave me. Since this car is ultimately destined for track day duty, I was going to replace them regardless for peace of mind. I have no info. at all on whether or not the wires/coils have been replaced. Again, on my short list of things to do - at least the plug wires, hadn't seriously considered replacing the coils as routine maint.

Next question - how to get it to a dealership. . . . . I'm assuming the warranty would cover the tow? Even if it's an hour trip one-way?

Plugs and coils should be considered routine maint...they need to be changed at least every 20k.

Call Mazda Roadside and see if they will cover the tow since the car isn't drivable with the clogged cat.

Other thoughts on flashing CEL are coils. You definitely should get them done. Should be $30 per coil parts and an hour to swap out all 4.

Also rough vibrations at idle could be a broken motor mount. There is an upgraded part for this. Motor mounts are ~$120-$140 each depending on which one is broken.

Start with coils though and don't let the dealer rip you off for some crazy amount of money.

Replace the cat. Samething happend to me.

I was having trouble accepting that the cat would go that catastrophically, so I called the service advisor at my "local" dealership for a second opinion. He, like some of you, felt it was most likely a coil. They had replaced a number of coils, but very few cats. I ordered a set of coils, plug wires and plugs (since I have no record from the PO of them being changed, even though he said they had). Long story short, it runs fine now - actually a tiny bit better - smoother, slightly more top gear pickup, even sounds different.

All the coils had what to me looked like "hot spots" on the underside - kind of a white, chalky look in the center of the epoxy (or whatever it is). The plugs didn't look appreciably worn, but the front plugs had noticeably more deposits on them. The contact on the top of the plug was rusted on two of them. I used dielectric grease on the boots of the new plugs. Hopefully that will keep any water out.

I'm probably going to make an appointment for a "check up" for next Monday since I already took the day off for other reasons and take them the plugs, coils, etc. and get their opinion.

Thanks for your help. :icon_tup:Between research, holidays and waiting on parts, the car was down a little over a week, but at least it's moving (rather well) under its own power without requiring a tow!

FWIW, onlinemazdaparts.com had the best prices on the coils and wires, and excluding Thanksgiving, had them to me in 2 days, while I got the plugs from RockAuto.com for $20/each including shipping and got them in 3 days.

^good boy! doin research on where to find the coils and plugs.

Glad to hear things are working better now. Good job!

So did you get your cat replaced? If not I would have it checked because it's most likely dead from the coil failure.

yeah, if your cat was glowing red its probably toast.

clogged cat like me. the dealership doesn't want to replace mine "yet"..hopefully they replace yours.

If they dont cover under warranty. I have a OEM cat forsale

No, I have not had the cat replaced. Nearest dealership is an hour away. Not exactly convenient. I was considering taking it in next Monday, but we'll see. Entirely too much to do between work and home to spend what will most likely be a 4+ hour adventure without having a concrete reason.

Those of you whose cats are, or are suspected to be, toast, what were the symptoms? The car is strong, and extremely responsive. To my butt-o-meter, it feels as good, if not better, than it did when I bought it 9 months and 6000 miles ago. The car ran a total of 3-4 minutes (and flooded as a result, BTW, so now I know what that feels/sounds like) - just enough time to back it out of the garage, sit for a minute contemplating the symptoms and then pull it back in the garage, so the cat spent minimal time red-hot.

argggggh this just happened to me, i was actually just putting stock exhaust back on & i finished a=so started it up. yesterday it was running awesome!!!!!

basically started it up ran for 10 seconds then i heard like poof an then the engine was stumbling an running rough, engine check like started to flash, could smell burning an looked under the car an the cat was glowing. i didnt want to shut it off so it didnt flood but who knows now.

any help.. i may just knock out the cat internals we dont need them here..

Flashing CEL is a misfire.

ok well i just gutted the cat anyway because it was glowing but now still misfiring & backfiring, will pick up coils leads an plugs.. thankfully not my daily driver but boy does it frustrate you!