83

What should I be checking?

The truck generally drives well,
but I’ve noticed an exhaust smell (not rotten eggs) when climbing a pass, less power than I’m used to (but not too
significant), and I’m averaging more like 17mpg. I’m used to a solid (though disappointing) 19mpg highway almost no matter how fast or slow I drive.

Seems like somethings clogged up or starting to fail.

Early this spring I replaced the plugs and air filter hoping that would help the reduced mileage. Didn’t help, and the exhaust smell started not long after.

2ToyGuy

Plug wires, and the O2 sensor are valid possibilities. Also, is the ground wire from the heads to the body in good shape? That's where the plugs get their ground. Bad ground, weak spark, etc. The O2 sensor just in front of the cat (s) helps the ECU set the mixture, so if it's bad, the ECU defaults to a full rich condition. Lousy mileage, weak on power. Something to check.

Are there any codes being shown? Is the check engine light on? Get a reader from a parts store and check. Make sure you clear any old codes out before you do, though. Pull the EFI fuse for a minute or two, then run the engine and see what codes pop up on the reader.

Let us know what you find
Pat☺

83

Thanks! Should have mentioned that - no codes.

plug wires were done about four years and…almost 100,000 miles ago but I assume they’re ok. O2 sensor is definitely something I wondered about. What about the cat?

I’ll look into those things.

2ToyGuy

I wouldn't presume the plug wires are good after that long. You can do a quick, easy check of them, if you want. Look at them in the dark. Like at night, no moon. Look for little lightning bolts from them. Any sign of lightning, they're bad.
Alternatively, you can ohm them out. I'm not certain of the required value, but it's in the FSM.
If it were me, personally, I would just presume they were bad, and replace them. That's just me, though.

The cat could definitely be bad, but they don't generally go bad without something from the engine causing it. Running too rich or too lean for any length of time, for example.

Good luck!
Pat☺

fierohink

I too wouldn’t skip wires after 100k miles of service.

83

Alright, thanks. Well against everyone's better judgement (including my own), I'm throwing money at the problem rather than going through proper diagnosis. I'll install new O2 sensors and plug wires and see if anything changes.

83

Yikes, I almost thought I'd need to pull the transmission to get to the front O2 sense wire...but going in through the gear shift hole worked. Will need to replace those nuts, too. The fronts we "ok", but the rears were too corroded for a wrench. Needed vice grips.

Will see what effect they have. It's possibly my imagination, but this morning the hesitation I've been feeling seems to be gone...I've felt this for almost 2 years now, and thought initially brake drag or a wheel bearing...It's not on acceleration, it's when I let off the gas, I hadn't been coasting as well as I remembered. Seemed to slow down like something was dragging. Not sure why that exact symptom would have anything to do with O2 sensors, but who knows. May just be my imagination.

Anyway I pull my trailer over a couple mountain passes on Saturday so we'll see if the smell, lack of power and poor mileage are gone.

I'll get around to replacing the plug wires sometime next week.

wyoming9

iTrader: (1)

If your smelling your exhaust while driving you have a leak in the engine compartment the only way while moving your exhaust is being drawn out behind the vehicle.

Your smelling this with no other traffic ahead of you for at least a mile?

83

No, this is on the interstate, with other people around. I'm fairly confident it's me because I've never noticed this smell before, and it started when my lack of power/poor mileage started. It's not the smell you'd get from the tailpipe - it's a bit off. Like I mentioned, not rotten eggs, but off.

I'll check for leaks. No exhaust manifold leak noise.

wyoming9

iTrader: (1)

Slop something on the exhaust that is burning off??

Fumes from the Charcoal Canister but the should trip a code.

The OBII system is working like it should??

83

Definitely no codes. I don't have a scanner, so I'm not sure. I should take it to the parts store and get it scanned...I'll try to do that this week.

83

Rather than spending the same amount of money to buy a diagnostic tool, I brought it to a mechanic for diagnostics...

Catalytic Converter.

I'll be checking out prices soon. Hopefully l can get the old one off without too much trouble.

83

Does it matter what direction I install the cat? There are no markings on it, and to my eyes it looks perfectly symmetrical. A quick google search gave me mixed messages...

There is a heat shield which obviously needs to go up toward the bottom of the truck, but otherwise I can't see any clues to whether it needs to go one way or the other.

Rock Auto listed this as a BRExhaust brand cat, but the box that showed up is Magnaflow.

2ToyGuy

Not that I'm aware of, but check VERY carefully for an arrow, even a small one anywhere on it. Also, check both ends carefully for an annotation of IN or OUT. Either one of those two items might be an indication of direction of flow. Different sized pipe openings might be an indication, too, but I doubt it.

As far as I know, they flow either way equally, but I'm NOT a big exhaust guy. You might e-mail the company it's from, or Rock Auto, to ask. Can't hurt, and it might matter a lot.
Or maybe stop in a local muffler shop and ask them. I would think they'd know.

Might not, too...
Pat☺

83

Thanks. Haven't heard anything definitive yet, but I did find a forum online where a guy said he talked to Magnaflow and they said that if there aren't arrows or an "A" and "B" side, then it doesn't matter which way it goes. I did leave a question on the Magnaflow site, but so far no answer.

I'll check it really close before install. Hopefully today, depending on how much trouble the corroded bolts give me.

2ToyGuy

From what I've heard on these forums, PB Blaster is a very good penetrating oil, very useful for rusted up bolts. I've personally never used PB Blaster. I use 3-in-1 Oil, and/or WD-40, and both have been very useful for me.
An impact driver is also quite effective, especially when used in conjunction with a good penetrating oil.
Also, a good long breaker bar is effective very often, especially when, once again, used with penetrating oil. If you have to, you can add a piece of pipe to the breaker bar to get even more "ooomph" applied to the bolt. I call it a Torque Amplifier

I realize scheduling may prohibit, but it's a good idea to put whatever penetrating oil you use onto the bolts, and let it soak in for a good long time. A few days, with added oil ever 6 hours or so, gives the oil a better chance to get down in and do it's work. Even a soak of a few hours, with added oil every hour or so can be effective. Better than nothing, yes?

If I recall the bolt setup on the cat, even if you break them off, you should be able to go to a hardware store and pick up some replacements. Just make sure the replacements bolts and nuts, are the same of better hardness, etc, as well as length, thread count, etc. If one or more do shear, they should, and please note the use of the word "should", just drive right out, unless they're REALLY rusted in there. If necessary, use a nut cutter (gad I hate that name for a tool!), and then drive the bolt out.

Anywho, I wish you all the best.
Pat☺

83

Thanks.

I started putting PB Blaster on them a few days ago.

The problem with these, and most exhaust bolts in my limited experience, isn't that they won't break free, it's that in trying to get them to break free, they round or snap. With my O2 sensors, I got away with using vice grips. On the cat, which I replaced yesterday, the front two bolts came out without issue. With the rears, which have welded nuts (fronts didn't for some reason), I had more trouble.

One snapped off, but it snapped off close to the nut, so I actually got a good length of bolt out and it didn't keep the cat from coming out. The other wouldn't budge. Not with the PB Blaster, not with heat and hammering. The bolt head quickly rounded. With both rears, because of broken or stuck bolts, I needed a sawzall. I cut both welded nuts as close to the base as possible. Got 4 new bolts/nuts from the hardware store. I read one review of the Magnaflow cat where the guy needed to get OEM gaskets to get it seal correctly. I ordered some. The ones that came with the cat are significantly thinner and more narrow than OEM.

My front sealed well, but the rear has a small leak. When the OEM gaskets show up, I'll need to work on the rear. when I cut the welded nuts, the bolts were obviously still in there. I needed to hammer the last little bit of bolt out, and I bent the base a bit. I hammered it back into place but I'm guessing it's still a little warped. I'll need to try to get that a bit more flush, and hopefully between that and thicker gaskets, it'll seal better.

2ToyGuy

Sounds like a job of work for sure! I'm glad you got the new one in OK though. I know there's still more to go, but I think the worst is past.
A thought I had, and I get so very few any more: Can't you use anti-seize compound on the new bolts so they are easier next time, if there IS a next time? Just be cautious, as I understand that anti-seize makes the torque values change. I'm not certain just how, but they change. When I did the head on my 87 4Runner, back in 2000 or so, I used anti-seize on all the bolts involved in the exhaust system I needed to remove and reinstall. Really, just the ones holding the pipes to the head. I torqued them to the values specified in the FSM, and they're all holding fine, so I may well be off about this.

Don't forget to clear any codes you had, too. That way you can be sure that any that come up are new.

Let us know how it runs, now, too. I'm curious...
Pat☺

83

I’ve considered anti-seize. I DO hope there isn’t a next time, but…I’ve said that before.

Not sure how much a small exhaust leak will affect performance, but next time I get out on a mtn pass I’ll let you know how it drives.

I’ll be driving over a couple before I get the new gaskets.

Oh, and it never did throw a code.

I'll say the cat smelled really bad the first time I got out on the interstate and really got it hot. But it seems to have burnt out any manufacturing chemicals or seasoned itself or whatever needed to happen. Doesn't seem to smell much today. It almost smelled like I was burning my clutch.

And to keep adding onto this, I'll mention that the heat shield, on what I'm confident assuming was the original cat, was facing down toward the ground. Not sure what's up with that...a mistake? Or intentional? I don't know. I installed the new one heat-shield-up.

2ToyGuy

All 3 of mine are on the bottom, and they're all factory. At least the cats are. I do beat the heck out of the cat once a year or so. A friend of mine, a professional mechanic recommended it, and it seems to make a difference. Of course, he also told me the best thing to do with it was to pull it off, stick a big screwdriver in it, stir it around really well, and dump all the stuff out. Then put it back on. Of course, there was no testing in Yuma. The farmers put more crud in the air than ll the cars could ever do.

Anywho, the heatshield is there to at least try to keep from setting fires when bouncing around off-road. That's why they're on the bottom.

Have fun!
Pat☺