O2 sensors

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

Hi guys, I've done a bit of a search but couldn't locate anything on this... I'm wondering if anyone can advise of where the upstream O2 sensor(s) is/are? I've looked the exhaust over from the manifold and down a bit under the car but can't seem to find it.

The car's losing power and running a bit rough when driving up long steep hills at speeds and it reduces the car to 50/60km'h max until I hit flat roads again. All other forms of driving including accelerating hardish when entering the highway are fine. When the engine begins to struggle and die a bit on steep hills the engine light comes on and remains on until the car is switched off.

I replaced the rocker cover gaskets, spark plugs and plug seals a couple of weeks earlier and that job went without hitch, so that can be ruled out. I'm thinking the upstream oxygen sensor is due for renewal. I'll get a diagnostics check done by super cheap auto soon and will get them to print the fault codes for me. That will hopefully tell me which sensor it is throwing the fault if it is in fact a sensor, or will let me know what the cause is. But in the mean time I'd like to check the sensor and clean it to see if that improves things when driving up a long steep hill which I have to do every day to go to work.

Just in case people suggest the following as a possible cause, I believe they can be ruled out. Air filter - it's clean. Fuel filter - it's only been in for 25,000km. I don't think it's spark related as it only happens on steep hills. I don't think it's fuel or air related. I lent a thought to it being the catalytic converter but I really don't want to remove it and clean it as a weekend project if I have the choice. I will if I absolutely need to but have you seen those rust seized bolts and nuts Plus an issue with the cat is almost always caused by something else creating a knock on effect, like a faulty O2 sensor.

I look forward to your replies.

[RanJ Avid PP Poster! Find all posts View Profile Close RanJ]

Well mate... I'm going to send you back to the drawing board! The petrol V6 Prado does not have o2 sensors or a catalytic convertor!

Because of it's tare weight and gross weight the vehicle is classified as an ADR34 Light commercial. Negating the need for these items.

These engines run from their knock sensors and timing for fuel mapping. So... check your timing.

I had the exact same issues and changed my timing belt. Brand new rig after that... scare the crap out of v6 commodore p platers when I take off from the lights!

[LeighW Avid PP Poster! Find all posts View Profile Close LeighW]

Did this start after you did the work on the engine?

Have you filled up recently?

If it happens only when climbing step hills it could be heat related, does it ping?

You wrote you changed the plugs, are you sure you use the right type and heat range?

If it started after you did the work, check electrical connectors, hoses etc. Check right
plugs have been used and chech the spark plug wiring etc.

[RanJ Avid PP Poster! Find all posts View Profile Close RanJ]

Also... super cheap wont be able to read the codes. But you can do it yourself using a paperclip and counting the engine check light flashes when you turn on the ignition.
http://www.troublecodes.net/toyota/ the first handdrawn image shows you how. Its for a 89-94 toyota but since the 90series prados are not obd2 compliant they still use this system.

From memory though... no light while driving means no codes stored.

[Brett1979 Avid PP Poster! Find all posts View Profile Close Brett1979]

Thanks for the help guys. That's good that it doesn't have the o2 sensors and cat. One less thing that can go wrong I suppose. I thought all cars post 1996 had to have them so assumed my car did, but that's good it doesn't. I was confusing the resonator for being the cat even though it looked a little different.

The car started with this issue 2 days before I changed the spark plugs thinking that may have been the source of the issue or maybe a coil pack or something. I bought Bosch spark plugs suited for my car at S'Cheap Auto and they were in much better nick than the ones which came out of the car that's for sure which were replaced 2 years earlier. I would've bought NGK plugs but there was no part number folder in store for them, so bought Bosch ones which did have the folder. As soon as I went to ascend the range going to work the next day the same issue happened, and the day after that and the day after that.

And a week before this my car was dripping a bit of coolant. I traced it back to the thermostat housing (praying to god it wasn't the head gasket). So I replaced the O ring as well as the thermostat while I had it out since it's a cheap part. Put it all back together and proceeded to top up the coolant.... Then before you know it, coolant was leaking from from the thermostat housing which puzzled me. I really hate having to do the same job twice. I bought a tube of Permatex grey to help seal the two metal mating surfaces. I applied a very thin light coat even though both surfaces were clean and flat and let it sit for 24hrs before topping up with coolant and starting the car and it worked. No more leaking.

Lucky me I got to use the Permatex again for the half moons when replacing the rocker cover gaskets.

Thanks for the info, I'll do the paper clip test to hopefully find out the issue and will look into the timing belt replacement. It's not due for another 50,000km yet so wouldn't hurt if I did. I'll do almost anything at this point to try and fix it as its a tad annoying.