Misfire, Red hot cat, runs like hell

Hey guys -

I have a 2000 automatic V6 that all of a sudden started misfiring really bad tonight, and would not hardly run at all. Looked underneath, and the catalytic converter was glowing red hot. From what I'm reading, it sounds like a bad O2 sensor, oil on plugs and wires, clogged cat, or a combination of some or all. Anyone have any experience or insight on this? Thanks!

 

Unbolt your catalytic converter and see if it runs better.

 

You'd be surprised how much trouble a bad O2 sensor can cause. If the CEL is on, check the DTC and go from there. Good luck

 

Check engine light has been intermittent over the last month or so - it would come on for only a few hours once a week. So I didn't think much of it. During this issue last night, it never came on at all.

Would the bad cat cause the misfire, or is it more likely that the misfire caused the cat to do that?

Somebody else mentioned that the mass airflow sensor could be causing all of this. You guys know anything about that? Thanks for all of the replies!

 

You might have a pending code (ie no CEL, but code is still there), have you hooked a scan tool up to it yet? Running too lean or too rich can cause these symptoms, which might mean mass air flow sensor or O2 sensor is bad. If it is running lean, I wouldnt let it go for too long.

 

Pulled the MAF sensor, cleaned it out really good, no dice. Trying to get a hold of my buddy with a scanner, but he might be out of town. Would a bad O2 sensor cause the misfire, loss of power, etc? Or just the hot cat? Could it be a timing belt issue? Please say no...

 

Sounds like a clogged cat, especially with the red glow you noticed, I had a cat clog once, finally made it home, got so hot it melted the rubber hangers...


If you can, like previously mentioned, unbolt cat, see if it runs better.....also when the cat is off, look into it with flashlight, the honeycombs let loose and clog the sucker up real good, causing excessive heat...sometimes you can get the clog out, or most of it out, put cat back on and get a few more miles while saving up for new cat....

 

Thanks for the tip - I'll try it. If the cat is the culprit, would I notice an immediate difference, or does it have to run a while?

 

You'll notice immediately!! It will feel like a race truck compared to what you've been feeling!

 

UPDATE: This weekend I changed all of my plugs, wires, air filter, and cleaned the throttle body thoroughly. It is clearly firing better, but there is a distinct plastic knocking sound behind the timing belt cover... it is still misfiring and does not have power. There is virtually no compression.

It sounds like my timing belt is frayed, and a piece of it is actually hitting the cover. I think I actually jumped a tooth when I punched it right before all these problems started happening.

My question is, if this is the case, and I have a frayed belt and a jumped tooth, wouldn't it make sense that since the timing is off so bad, the cat would glow and I would have no power if the fire, air, fuel, compression sequence is off; and the cat is where combustion is taking place?

 

Wow, How many miles on your Taco? Has the belt ever been changed? If it has when? Mine was first changed at 130,000 but i see the manual recommends you change it at 90,000.

 

It was originally changed at around 100K - now I'm over 210K, so it makes sense that it would go. I'm just trying to figure out if a failing belt could cause all of these issues - especially the glowing red cat.

 

If the timing belt is a tooth off, it'll run just like you described. Very bad miss, low power, etc... Although I've never seen a belt jump a tooth as they usually break, I suppose it's not out of the question. Stop running it if the cat is getting hot enough to glow. You're dumping unburned fuel into it and you'll plug it up - may already have - and can end up with a fire. I witnessed a mid 80's cutless (customer's car back when I used to repair them) go up in flames due to unburned fuel plugging the cat.

 

At the very least it sounds like your cat is clogged. The timing sounds off as well. Time to park it or take it somewhere.

 

A friend of mine had a truck once that basically had no compression on one of the cylinders, so all of the unburned air/fuel from that cyl was getting pushed out on the exhaust stroke. and the cat was doing what it was supposed to be doing and burning off all that unburned fuel, and getting waaaaay to hot in the process.

You need to track down the cause of your misfire, fix that and your cat should no longer glow red hot.

 

Sounds like that's it then. There is an unmistakable plastic knock against the timing belt cover, so obviously the belt must be frayed. It must have jumped a tooth and frayed in the process. It's parked at my buddy's house, and he's tearing into it tonight or tomorrow. Definitely an interesting problem in which I'm learning a lot in the process. I'm just glad that thing didn't break on me.

 

And here's the culprit.... any tricks to changing the timing belt on these? Does the radiator have to come off?

 

I haven't even looked to see how much room there is for changing the timing belt. But I'd take out the radiator anyway even of there is enough room because you don't want to poke a hole in it if you drop a tool nor do you want to cut up your knuckles if you slip a wrench. Also, I've found the antifreeze typically needs to be changed too due to miles on the engine. So this is as good a time as any. Does the water pump run off of the timing belt or is it behind the timing belt meaning you'd have to take the timing belt off to change the water pump? If so, change that too. Also, don't forget to replace the timing belt tensioner. Check the pulleys for wear and replace as needed.