P0171 or PO171 (1 Viewer)

[izzyandsue]

Gang,
I got a new code today, truck hates me sometimes... I had the P0420, which started after I installed the sliders and had to move the cat converters some to get the sliders to fit. So thinking a leak was causing that. The 171 is a lean condition, done the read-search and removed and cleaned the MAF. There was definitely something in the chamber that I removed. So thats done, and the intake pipe and gasket are new and look fine. Havent driven since the cleaning the MAF, will do tomorrow and see if code comes back up.
By the way, truck is running great, no hesitation or power loss.

The exhaust is my next potential culprit, and I did notice a nice new "bang" on the pipe after downstream from the second cat, must have happened on the trail this last weekend. What I read is that an exhaust leak or bad O2 sensor could cause it. Since I suspect I have a leak already for the P0420, could the 171 be triggered by a "bigger" leak?

Any thoughts appreciated. Didn't see anything else on my search.

 

[slceso]

When I was getting those on my 95 I believe it was due to substantial leaks upstream of my cats and O2 sensor. First you get the code for high post cat O2, then I think the ECU goes into closed? loop, then you are getting the lean as a result. Kind of like it can't tell if your cats are working so it fails safe and leans out the fuel. You can run like that indefinetly, but economy will suffer.

TBH, this is all from memory from a few years back. You probably have exhaust leaks/bad O2 sensor.

Edit: and when I say substantial, I mean the cat ended up getting torn off and I just ran like that.

 

[izzyandsue]

I hate all cats. But yeah, I can see that and makes sense, specially since I did play "bang a gong" with the exhaust last weekend. Will check out the system when I have time with a flash light, could be cracked.

 

[slceso]

It won't have to be a big one either. Mine started as a circumferential crack where a new cat was welded in. I could clear the codes when it was running and they wouldn't come back until it had been off and cooled down (I guess drawing in outside air to the post manifold/pre-cat). Or maybe it was a significant enough leak that exhaust wasn't really going through the cat and that's why the ECU though the cat wasn't working.

 

[izzyandsue]

I like this

 

[izzyandsue]

That idea of blowing with the shopvac worked great! Here is what I got, one small leak after cat 1, and one major after cat 2. No leaks on the O2 sensors, they both look a lot newer than the cats. Checked the rest of the system, the Y pipe, no cracks.

The bolts holding the glanges and gasket look really rusted out. Will try to get them apart this weekend and maybe add more gasket in between. If that doesn't work, will need some professional eyes on it. Someone else in the forum recommended this:
Amazon.com: Blue Magic 18003 QuikSteel High Temperature Metal Repair Blister Card - 3 oz.: Automotive

Between the 2 cat converters


Big leak here, no wind, thats just air coming out from the flanges

 

[Roxx]

You may need heat to get the bolts out. Also get a grinder and grind the flange as flat as you can for the seal to sit right. If not you are going to end up like me changing the gasket and changing it againg because the new one didnt seal.

 

[izzyandsue]

You may need heat to get the bolts out. Also get a grinder and grind the flange as flat as you can for the seal to sit right. If not you are going to end up like me changing the gasket and changing it againg because the new one didnt seal.

Is it worth to double on the gasket? Did you get it from Toyota? This maybe a bigger project than I thought....

 

[slceso]

I fought mine and had repairs done a few times until I lost the cat in a snow drift one morning. Maybe just hit a muffler shop. On mine they had cut the flanges so I kept trying to make weld repairs and and it kept failing because of the rust. I tried different diy repairs and never could get it but YMMV.

 

[Roxx]

The old gasket eats in a grove. When it comes out you have to grind the surface to reduce yhe grove or it wont seal. You can use double too. I used factory gaskets.

 

[izzyandsue]

Well, done for now. I was able to remove the rear cat bolts, used naval jelly to remove most of the rust( worked well), then map gas heat, put a wrench to the nut and the bolt sheared right off. Then punch and hammer to remove the opposite side.
The upper was more difficult, hard to reach with sliders. Same treatment, but then the wrench began to turn both sides, nut and bolt. Usual tricks didn't help, so i used a chisel to hammer it into the space between the faces to give the bolt some traction, world, repeated the process until I had enough separation to use small hacksaw on the bolt. Then one final wack with he chisel and bolt broke. Houston, we got separation.

Old gasket

Used angle grinder as much as it would fit, on the cat face it was easy

 

[izzyandsue]

Then on to Scott Clark, they had both gaskets so I got both. Then some m8 40mm hardware grade 8 to suck it down.

This is the one that goes on the second cat per dealer.

When I fit it, it was very lose, so used the other one that fit like a glove.

But the soapy water test failed with one, so installed both and cranked the down. Zero leaks, hope it stays like that. I am leaving the front one alone me for now, those bolts will not be easy to remove with the slider there. And too lazy to remove slider for now. Will drive later to test is code comes back

 

[izzyandsue]

Got a 20 mile drive, mixed mode, turn it on and off to cycle the ECU, and so far no codes. Hope it holds! Gorilla Glue epoxy on radiator holding good to, no leaks there.

 

[Malleus]

Izzy,

Try 50/50 ATF/kerosene on the bolts. You'll have to paint them over several days, but it should eat through the rust.

There's a sexy recipe for this, but it contains a lot a stuff you don't need, because it wasn't originally designed for rusted bolts.

 

[izzyandsue]

Thanks! Seems like Naval Jelly did the job pretty good. And the codes have not returned!

 

[Malleus]

Naval jelly will remove exterior rust, but it's too viscous to penetrate assembled threads. That's what the special sauce is for. I used to use Naval Jelly for exterior rust and Liquid Wrench for assembled parts, but the 50/50 is much better. You do have to give it a chance to work, though. If you're in a hurry, a flame wrench is a better option.