RED HOT CAT & P0300 (random misfire)

[_rgk]

My cat was glowing red hot today. I have a misfire and a rich condition indicated by a P0300 and blinking check engine light. Would a broken cat (hole in the honeycomb) cause a rich condition? I know the cat is damaged, but am not sure whether something else isn't causing the problem. I have a P0300 and a P0421.

 

[agr99]

I cant explain it glowing red hot.but p0421 is warm up catalyst below threshold which your precat. could be 02 sensor, or coil pack.

 

[duren03msp]

clogged cat. the exhaust gets backed up in the cat causing it to glow red hot. get it replaced before the car catches fire. I've only seen it once and once the cat got replaced it was fine. which cat was it? primary or secondary?

 

[tweety2300]

Get the misfire fixed first so that you don't kill another one

 

[duren03msp]

^^^ that's a given

 

[_rgk]

Yes, for sure the upper cat is bad. There is a hole in the honeycomb. I heard that a rich condition causes too much raw gas to go inside it and heat up the cat. I am going to replace it.

My question is, is it possible for the bad cat itself to cause the misfire and/or rich condition? Perhaps if it causes too much exhaust buildup?

I am having some trouble tracking down the misfire. Purchased new plugs today. I am suspecting the following: I had crushed my valve cover gasket and it was causing oil to leak into the spark plugs. I have replaced the gasket, but the misfire persists. Perhaps this is because the plugs were coated in oil? I'll find out when I replace the plugs.

The springs that connect the coil packs to the plugs may have been coated as well, perhaps by burning oil fumes. I cleaned these out and the problem went away for a while, until the plugs got coated again (because I had not yet fixed the gasket). Hopefully new plugs, cleaning the springs, and a new cat solves all these problems.

Final question: I'm at work and have to get the car home (10 mile drive at highway speeds). should I drill a hole in the cat to allow exhaust gases to escape?

Thanks everyone!!

 

[tweety2300]

More than likely the miss fire caused the cat to go bad. Coil packs are only $60 new. I would go ahead and replace coil packs plug wires and plugs if you can afford it to be safe.

If you drill a hole in it it's gonna be loud and possibly melt anything not metal around it. Shouldn't hurt it for a 10 mile drive just snag a fire extinguisher from work and pay attention to any funny smells

Edit: not snag as in steal. Just ask to borrow one

 

[MaxPower]

Agree you should definitely replace the coilpacks and wires.

 

[_rgk]

I just ordered a direct-fit, NY-legal, Walker cat. The coil packs resistance values are within spec. The coil springs, however, had only a "1" resistance value until I cleaned them, which is why I suspect them and the plugs. Usually the misfire occurs only AFTER the car throws the P0421 code. Meaning, if I reset the computer all is well until a little bit after the CEL illuminates once again, and usually after the car warms up (about 10 mins of driving at highway speeds). The car idles beautifully at about 750 rpm most of the time. Of couse, if cleaning the springs once again, changing the plugs, and replacing the cat does not help, I will look into replacing the coil packs.

 

[duren03msp]

too bad you bought a new cat. I have one off my '02 ES I could've sold you. almost brand new. could've saved ya some money.

 

[agr99]

Id replace the coils even if you replace the precat. When people dont usually the same thing happens again.theres a few threads on replacing it and why replacing the coils after are a smart idea

 

[tweety2300]

I just ordered a direct-fit, NY-legal, Walker cat. The coil packs resistance values are within spec. The coil springs, however, had only a "1" resistance value until I cleaned them, which is why I suspect them and the plugs. Usually the misfire occurs only AFTER the car throws the P0421 code. Meaning, if I reset the computer all is well until a little bit after the CEL illuminates once again, and usually after the car warms up (about 10 mins of driving at highway speeds). The car idles beautifully at about 750 rpm most of the time. Of couse, if cleaning the springs once again, changing the plugs, and replacing the cat does not help, I will look into replacing the coil packs.

Precat on the protege is very sensitive. Bad coil packs will cause it to go bad. Even a bad o2 sensor will let it run rich enough to ruin it. Coil packs can also test good and still cause misfires and not enough to make the cel come on but enough to ruin the pre cat over time

 

[_rgk]

Is it wiser to get the OEM coil packs, or are there any aftermarket brands that are worth looking into?

 

[03protolx]

Your local autozone/oreilly auto parts will have a aftermarket coil pack replacement for around 20-30 dollars a piece, which at the dealer it cost about 2-3x more. Many will disagree with me, but i typically just replace the coils, wires, and plugs all at the same time around every 50k miles.

I've had the autozone coil packs in my car for the past few months and have been doing just great. if i remember they were $25.99/pc.


Catalytic converters are extremely sensitive in a ride range of vehicles, not just mazda proteges. you could always just gut the cat out after you fix the misfire to relieve some of the pressure, but it is strongly advised to replace with either a factory unit or a high quality aftermarket unit like walker.

I replaced the cat in my 99 dx with a walker and drove with it for three years without fouling it.
The original cat on the 99dx lasted to 113k miles, due to a failing coil pack. (1.6L)

 

[MaxPower]

You could also get the Hitachi coil packs (part #IGC0071), which rockauto claims are OEM. They are $59/each, which is more expensive than the other aftermarket coil packs, but cheaper than the ~$90 coil packs from Mazda.

 

[_rgk]

Replaced the cat and she's running well. Engine threw a P0135 after the replacement, but I cleaned and tightened the O2 sensor connection a couple of times until it went away. I have not driven the car enough yet to see if it throws a P0421. I would like to get an exhaust gas readout done to see how I'm doing, but not sure if there is a DIY way of doing this. I would also like to get those coil packs replaced.

 

[03protolx]

Replace those coil packs, asap. Theyre cheap and good for precautionary measure. Replace plugs and wires, too.

Glad you got it all taken care of though, what brand did you go with?

 

[_rgk]

Walker EPA Ultra Direct Fit Converter.

 

[_rgk]

Arrived at work this morning and smelling that odor again... like melting plastic. It was the odor I smelled when the first cat glowed red hot. I'm hoping it's the new welds burning, but maybe I should ride the bike to work until those new coils arrive.

Car is idling a bit low, about 675-700 rpm.

I'm getting vibration at around 50mph and over. I used to think it was the tires - they are worn and probably out of balance. But the steering wheel does not shake much and I could have sworn the shakiness improved when I first put the cat on two days ago. I'm also feeling that the idle at start up may have been a bit better when I first put it on. So I'm thinking the shakiness might be backpressure.

I did get a very strong, distinct odor the first time I drove the car after putting the cat on, definitely new welds burning. But at this point I'm not sure whether they're still burning or whether the cat is overheating.

Besides bad coils, why else would the cat be overheating? Is it possible I didn't break it in correctly? Upon installation I let the car warm up at idle. I then drove it for about five minutes, about 1.5-3.5k rpm, and let it cool down for twenty minutes or so.

I later read you're supposed to let it warm up at idle, then run it in park at 2.5k rpm for two minutes, then cool it down. Does anyone know how strict this break-in procedure is?

No check engine light. Am I being paranoid?

 

[03protolx]

You should be alright. Every time i've replaced a cat, there was a metal-burning smell for a short time but went away.

If the check engine light isn't on yet, it should be alright. I definitely would but your bike to good use for now though.

600-750 rpm is in the "normal range", my 2003 idles right at 600-ish.

If its struggling, wanting to stall out....clean your egr/or replace it.