Noil

I'm having a odd problem with catalytic converters. I've gone through 3 of them in 2 years. What is happening is that the internal baffel and mesh let go and block the exit out of the convertor. This has happened with several different brands of convertors. Not running anything crazy for motor. The first two happened with the stock 3.4L V6 and the last one which only lasted 6 months occurred after engine swap from a 2001 4runner with same 3.4 V6.
Not doing any major off-roading or throwing any engine codes. Anyone else ever have this problem?

millball

Are they getting too hot?? Exhaust stream with too much unburned fuel can make 'em run hot.

Maybe you could compare temps with another similar truck using an IR gun.

wyoming9

iTrader: (1)

Just what brands ?/

I have close to 100,000 miles on my Walker Converters with no problems

Your OBII systems are working ??

I gotta agree with unburned fuel

Noil

I am thinking could be unburned fuel as well and it is burning really hot ... I can go about 10 miles and can smell hot exhaust around the convertor area while standing by the driver side door and rapid and loud tinging from super hot metal coming from the convertor. All the OBII system is working, unfortunately don't have a ir heat fun or access to one I live in a very remote part of Canada now.

I did have twice fuel burning too rich on bank 1 code twice; my airbox was all jumbled up and out of alignment, I fixed that a few weeks ago and no more codes.

Noil

For the brand have used magnaflow, don't know the first one was on the truck when I got it and had a exhaust shop put on the latest one so have no idea what they put on.

Noil

I found a Walker 15034 universal convertor that should work, do you know if that is the type you have had good luck with?

wyoming9

iTrader: (1)

I use the direct replacement ones .

That have the flanges on and bolt on.

I gotta think your having a real bad run of bad luck.

Your seeing this damage when you remove the cat??

Then this blockage does not cause any of the Cat related codes to trip

From all this material breaking up are you also changing the mufflers as well ??

Is this all on the same vehicle ??

Just how did the Engine fail if this is all the same vehicle ??

Noil

Haven't removed the one that is currently installed yet, doing that today, but yeah the other ones were pretty damaged inside. The last one I took off had the resonator (I think) let go and in the process a lot of screening material severely restricted the exit from the cat. I have changed the muffler every time I have changed the cat. Yep all on the same vehicle; I could see maybe if this was happening on different vehicles that is just the way things are but nope this 4runner seems to eat catalytic convertors. The roads here can be pretty rough but it is no worse than trails others go on, so I don't think that the jarring of the road could be contributing to the premature failure; and I don't drive very fast on these roads it just costs way too much in repairs and some of the roads have holes big enough to swallow your tire.

Previous owner abused the motor; and I am not exactly sure how he did it but somehow he managed to put a hairline crack in the cylinder wall of cylinder #3. As a result it was drinking coolant and ultimately developed more serious issues with compression as coolant seeped into the cylinder. So in November of 2016 I had saved up enough money to get a engine from a 2001 4runner with 66K miles and did the engine swap. In March of 2017 all new exhaust from the cat down so I was very surprised to see that convertor issue is still there.

Melrose 4r

You say three converters in 2 years, but how many miles a year are you talking about? In my personal experience, aftermarket converters have lasted me about 3 years/40-60k miles whereas OEM was much, much longer, more like 9 years at approx 15k miles/year. Of course, OEMs cost a lot more...

Noil

Average about 20 to 30 K miles ... Just got cat take off today was barely the width of a pencil open in it that one has less than 5K miles on it . They have been aftermarket ones.

Long update of what happened today ... A​​​​​s others have said it looks maybe like a fuel issue. This morning on my way to the shop in the city the motor threw the burning too rich on bank 1 code again. I have noticed that when coasting down long hills or down mountains that the idle gets really low ... Talking so low the motor sounds like it is going to stall out, this is usually when it throws the code about burning too rich on bank 1.

Could​​ not get another convertor today the shop didn't have anything and was going to be a few days before one could get here. So right now it is straight to the muffler.

Tonight on way home it actually did stall twice on me on both within a minute of each other. Went down steep mountain in drive (Automatic transmission), idle got low as it has been, slowed down to turn on to a side road and it stalled. Restarted without any difficulty drove maybe 4 yards pulled into driveway stalled again. Didn't do it again but after the second stall I only drove about 10 miles to get home. Before that I had driven nearly 200 miles with no issue including three mountains descents. Also no codes were thrown.

I know the back flow pressure has changed now but it was doing this almost stalling idle coasting thing before I had thought that maybe it was because the engine couldn't breathe right with the clogged convertor. However it's still doing it and now actually stalls out.

I think the two issues are related but I don't know.

The closest part store is about 150 miles away, so it will be a few days before I can get filters and sensors if needed and there may be an additional wait if the part store doesn't have it. I am going to replace the fuel filter even though it should not need to be replaced yet. Air filter was replaced last week. The O2 sensors were replaced 2 - 3 years ago not too sure on the life expectancy of them. The mass airflow sensor is the original and has never been cleaned to the best of my knowledge.

Thanks for all the help from everyone!


​​

wyoming9

iTrader: (1)

I gotta wonder if the raw gas being dumped in is the issue .

Add to that just a bad lot of Converters that just ended up in your area by pure luck.

Exhaust system secured with the Rubber donuts so it is supported yet has some flex ??

75w90mantraN

Rpm should go up when you're on the descend, only way it go down is if you put the trans on neutral. Something about that 66k engine isn't right. Unburned fuel is known to shorten cats life. Since pre-cat sensor was changed...I'd look at your plugs and see if they're coated in fuel.

How's the rpms when you're giving it gas going up the mountain? Stepping on the throttle too much on the climb is another way to send unburned fuel down the exhaust.

Noil

Did two tests one in overdrive and one with over drive off. EctPwr was on for both tests, I find it works best in this terrain.

In Overdrive going down mountain RPM was between 700 and 1000. With Overdrive off RPM was 1300 to 1500. In 2nd gear 2000 to 2500 rpm.

Going up mountain with Overdrive rpm was 2300 to 2500, with Overdrive off RPM was around 2400 to 2600. Didn't check RPMs in 2nd gear going up. Will check the plugs when there is a break in the rain, which could be Saturday or Sunday. Unfortunately don't have a garage I can pull the truck into and work on when the weather is foul.

I typically don't step down too much going up the hill just enough to get it up the incline, fuel at $1.35 / litre here doesn't encourage holding throttle down hard. But I do understand what you're saying about over stepping the throttle.

Noil

Update for today: I went and got a converter and after talking to a older mechanic at the dealership he concluded that the front O2 sensor is intermittently failing and is in the early stage of complete failure. I couldn't afford what the dealership wanted for an O2 sensor was quoted almost $400 for just the O2 sensor so I went and got aftermarket one from Napa and a converter both with lifetime warranty and fuel filter for less than the cost of the dealership sensor.

So when the rain stops will try and replace the front sensor. Hopefully I can break the bolts free without screwing anything up. Will also check the plugs for excess fuel too.

75w90mantraN

2-3 yrs on that upstream sensor and already failing? Has to be an aftermarket, do you know? Go OEM. Expensive up front but nowhere close to a catalytic, as you may have found.

Sucks to be in a county that requires emissions doesn't it.

I have an OEM
non-Cali upstream and downstream sensor (manual trans) I can sell you if you're interested. Part number 234-4161 / 234-4154 but I forget which is which. But it looks like you got a nice lifetime deal there.

Been over 3 yrs on my sensors. Just over 1 yr on magnaflow with a 5 yr warranty.

Good luck! Look forward to your update.

millball

I find that NTK O2 sensors are good as any and can be got for good prices on ebay or amazon.

They are Japanese made and high quality. Ford/Mazda used them OEM.

Denso sensors can be bought similarly if you shop around. Cheaper than one in a red Toyota box.

I have had terrible luck with Bosch and other off brands.

Noil

I picked up a NTK O2 sensor, was assured by NAPA it was a good one. The mystery deepens with the exhaust on this truck.

Found the missing sensor was not where it was supposed to be and hidden away.

75w90mantraN

So was the old sensor not hooked up? Weird case alright.

Case closed...? I hope.

Noil

They had it hidden behind some heat shield and I couldn't see it until I took the shield off. Still haven't pulled the sensor in part because the weather is still not great and also the nuts will not be salvageable. So I called the closest Toyota dealer which is about a 450 km round trip and they didn't have anything no nuts or studs. Managed to get a hold of my brother who lives in a fair size city and the Toyota dealership there is going to order in the replacement nuts and extra studs. Will be about 15 to 20 days to get them, so for now kinda of stuck waiting on parts.

In the meantime I have been spraying the nuts with PB Blaster hopefully that will make it a lot easier to get them off when it comes time.

Thanks for the help and advice from everyone. Will keep the group updated.

75w90mantraN

Suggest vice grips on them nuts. Worst case, if you have a reciprocating saw or cutting tool to make a cut on part of the nut, then hammer and chisel it off the stud thread without damaging the stud.

Must be isolated where you are.

Let us know how it goes.