I got the PCV valve out. The valve and the grommet broke into about 20 different pieces while removing them. I had to fish pieces out of the valve cover with a stiff wire with a hook bent into the end and with my shop vac. I should have a new grommet and a new PCV valve in hand shortly. I also ordered a PCV hose from Toyota. I think the MAF might have a problem. It's not measuring the intake air temperature correctly. I am pretty sure it was reading 50° warmer than the actual temperature. The front O2 sensor has got to have at least 100,000 miles on it. I say that because the nuts that hold it down onto the flange don't have a hex shape any longer. They have rusted away. Fortunately the studs and the flange on that combination head pipe and catalytic converter. I don't want to think about how much that would cost to replace. The rear O2 sensor looks slightly newer, or at least the exhaust system that is attached to is newer, but it looks like the gasket is falling apart. I will probably go ahead and replace them both

You need new gaskets. The new sensors should come with gaskets. My 96 had balls of rust where the nuts were for the front O2 sensor with 220k miles.


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Spray those studs for a feww days minimum. Spray it every day with pb plaster. Do it Every day after you order your sensors lol

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Lots of times these front 02 sensors go bad. My 97 5 speed lost it's at 118k miles. My 02 camry lost its front 02 sensor at 100k

I think I changed Tetanus 1 as well but I have to my excel sheet

Always check for vacuum issues like the other users suggested. Very common for a PCV valve to be stuck and buy a new grommet before you touch those things because 90% of the time its dry rotted and cracked if never changed.

These engines are mostly 20 years old and extremely easy to have a hose split cracked etc. In the vacuum line

Verify no exhaust leaks too.

Before changing these O2 sensors out pull open the Factory service manual and verify they are bad. It's super easy to check these with a meter and the manual tells you what the resistances are supposed to be. And it's better then replacing and finding out that is not the issue.



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Any tips on picking o2 sensors? I looked on rockauto.com and there are about a dozen or more to choose from ranging from about $23 to $160. I usually try to buy parts made by Japanese OEM suppliers for my Toyotas. I see that rock has Denso brand o2 sensors for about $44, part# 2344162, which is the same part that Autozone sells for $100. I'm also getting conflicting info on whether I need different sensors for the front and the back positions. Autozone says I need part # 2344161 for the front, and 2344162 for the rear. Rock says use 2344162 for both. Then Bosch and NTK complicate matters even further by using the terms "bank 1 sensor 2" and "bank 1, sensor 1", indicating different sensors for the different positions.

BTW I am going to consult with my local muffler guru and see if he can weld new flanges on to my pipes at both locations so I have a good base and fresh studs to install my new o2 sensors. Randy's Performance Muffler, in Lake Geneva, Wisconsin, is a gift to our community. He has extremely reasonable prices and does excellent work. And he's swamped. You have to get on his waiting list to get in.

Hi neighbor.

Checking this out, the xxxx161 Denso is for a non-Cali manual trans. Looks like two xxxx162 sensors are what you need if your rig is a non-Cali with an auto trans.

I have the best success here in Wisconsin carefully cutting off the nuts with a Dremel with a cutoff wheel, chasing the threads with an appropriate m8x1.25 die, and re-installing the new sensor and gasket with fresh m8x1.25 copper clad nuts. Don't even bother trying to loosen with a wrench as breaking a stud is a setup for way more work and expense.

Barillo, O2 sensors hardly ever code for old and worn out. Usually they only code for the heater circuit or when the heater circuit shorts to the sensor side and you get the code for higher than expected sensor feedback-threshold-......on the rare occasion one may get the slow response code.

Other than testing the heater circuit as per the FSM I am really skeptical on testing anything on the sensor side.


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The other issue that arises, particularly in the rust belt, is gasket failure. Not only does exhaust leak out, but oxygen-rich fresh air will leak into the exhaust stream messing up the sensor's reading. On non-Cali exhausts the front sensor controls lambda, the second one measures results of the first and health of the cat.

You are on point. I mentioned many times that exhaust leaks near the front O2 sensor will really mess things up due to what’s called “Reversion” where the exhaust pulses will actually suck fresh air into the exhaust stream and mess up both of the O2 sensor readings.

A friend of mine with a TACO truck with the 3.4 replaced his O2 sensor and didn’t put on the gasket and his lean code came back. I shamed him into actually installing the gasket and his code and check engine light went away on his next drive to work.


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Well mine did each time they failed the meter test. Gaskets were not leaking and when I replaced them my code was gone


When the meter tests fail the sensor I replace. Heater circuit goes. Thus kicking on the CEL

Yes we check the heater circuit of the O2 sensor as that's the section that fails

So when 1/2 the sensor is dead it's dead and needs to be replaced.

Well that's what I do.

Why would you not replace it?

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Since I'm already going to be replacing my oxygen sensors, I will probably just apply some heat to the nuts with a small welding tip on my oxyacetylene outfit. If I get them glowing red, I should be able to spin them off with my bare hands (after they cool of course). Well that might be overly optimistic, but certainly a pliers would do the trick.

I could be wrong. But I think those are single use nuts on O2 sensors like the 3 nuts on the header flange.


Anything exhaust bolts and nuts it's always best to heat then remove. Great plan along as you are happy with it.

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