1991 22RE Base Pickup, 5 speed, 200k miles, original engine

Hey guys -

So a recently and troubling issue has arisen on my 91 Pickup. Whenever I drive the truck for more than about 10 minutes, I get a mild headache. I believe this to be from some sort of carbon monoxide entering the cabin while driving. I have a carbon monoxide sensor which detects it in PPM, and I got a pretty steady reading of 5-9 ppm while driving on the highway yesterday with the windows down. The CO sensor only starts to give a reading above 0 after 5 or so minutes of driving. Today, on my way to work, I got a similar reading with the windows up. Both days resulted in a headache that lasted for about 15-30 minutes after I stopped driving. I do not have this issue with my other car (2016 Ford Fiesta ST) so I don't think it is related to driving in general.

What could be causing this? I had an exhaust manifold leak last year, which I fixed with new gaskets, so I doubt that is the issue again. I definitely have some weird-ish sounding exhaust, but I figured that was from the rust holes in my muffler.

The only thing I have recently done on the car is replace the 5 fuel injectors. I took the intake manifold off, but did not touch the exhaust side. I did have to unbolt the EGR pipe where it goes to the intake, but I replaced the gasket on there with a new one. I do not see any visible fuel leaking when the engine is running so I'm not sure if it is a fuel thing, although that is the last thing I touched on the truck.

How would I go about diagnosing this? It is obviously not safe to drive the truck as it currently sits, so I will (and have been) driving my Fiesta mostly, but I do need my truck sometimes and I miss driving it without poisoning myself.

 

This is a typical issue on 4Runner's because of the rear window. If your exhaust isn't routed to dump to the driver side/behind the passenger tire, you'll get hit with some exhaust fumes.

Being that you mentioned you have holes in the muffler and with the windows down, you might be running into the same issue.

 

Yeah makes sense - my exhaust is routed there, but I definitely have some holes in the muffler - I'll attach a picture below.

I'll probably just replace the muffler since I had been meaning to do it for a while. Is there any visual test to determine whether the cat needs to be replaced as well?

Here is a short
And here is a photo of the muffler:

 

You can take a look at the honeycombs inside the catalytic converter and see if there's any hard carbon buildup. Typically, my general rule of thumb is if it passes CA smog, leave it alone until it does fail.

 

With those holes in the muffler, you well could be getting exhaust fumes, including the CO, leaking into the cab from a number of places. I would absolutely get that muffler replaced ASAP. Personally, and this isn't an ad for them, really, I use Midas. My 87 4Runner's muffler had the inlet pipe rust/crack so it was totally loose, and there were a few cracks in addition all over the front of it. When we took it in, the guy said "You need a muffler, don't you?" I said "How'd you know?" He told me he'd heard me coming a block away
Anywho, that was in 97 in Yuma, Az. Last year, the same cracks started up again in the muffler. We took it into the local Mids here in K Falls, OR, and the replaced it free. Gotta love a lifetime Warranty! They ran the whole system for cracks, rust holes, etc, and would have fixed anything they found. Nothing showed, thankfully.

Anywho, point is, it's worth it, to me anywho, to go to a chain that has, and HONORS, a worthwhile warranty. Saved me a fair amount of money, this time around. As long as folks hold onto their Toyotas, these days, I feel it's worth the money.

No matter who, or how, you really do need to replace that muffler ASAP.
Good luck,
Pat☺

 

CO will definitely cause headaches. install new exhaust (it needs it anyway)

 

Do not screw around when it comes to carbon monoxide! https://www.abe.iastate.edu/extensio...icles-aen-208/

 

It used to be that you could buy cat-to-tailpipe from Toyota, but that's no longer an option -- obsolete. I do see some Walker options (maybe others), but I speculate they are of lesser quality and shorter life. With the one welded assembly, it's maybe 10 minutes to replace the whole thing: two bolts at the converter, and one at the tailpipe if your assembly didn't come with the bracket. Otherwise, it's just hooks into the rubber supports. Lemon squeezy!

PS: I thought I'd ordered the last exhaust assembly from Toyota through Amazon. Instead they shipped me a set of running boards for a Tundra club cab. Sure....those are almost the same.

 

Yeah I've heard that the Toyota part has unfortunately become unobtanium... I saw the Walker one (I think the same one you mentioned - p/n 46921?) as well as a Brexhaust one (which I think used to be Bosal brand). I got the Walker one and a few new gaskets / hangers. Hopefully this takes care of it!

 

Yeah unfortunately I haven't smogged it yet this year (although I need to) because I was having an idle issue and I knew it wouldn't pass smog when it was due. I seem to have taken care of that with the new injectors, but hopefully once I get the new muffler on I will be able to pass smog. Could a leaky exhaust be causing and intermittent cut out in power? I thought I fixed it when I replaced the injectors, but it happened again a few days ago, although only once and not since.

 

Thanks for the info, man! I really do appreciate it. I ordered a new Walker muffler and gaskets and I'll install it this weekend to see if that fixes it. I'll definitely check out Midas if this doesn't resolve my issue to see if they can do a full inspection of the exhaust system.

 

i installed a walker bolt-in muffler. Went great and sounds fine. I like the fact that when I dropped the transfer case it was easy to move the muffler out of the way and reinstall.

 

Awesome! I have a 2WD, so should be an even easier install, right?

 

About the same. Actually, mine might be slightly easier since i don't need to jack it up to crawl under there. If you ever need to replace the gasket the Toyota one should work fine, too.