I'm active on a Bonneville forum and the consensus there is to stay away from Bosch O2 sensors for the reasons you described.

 

you can use them if you are working on a German car, LOL.
I believe there is only 3 supplier for O2 sensor. Bosch makes them for German car and Some Ford for a period of Time.
The other is Japanese manufacturer, either Denso or NTK(NGK). All Asian Import, Chrylser, and GM use either one of them. You can Mix Denso and NTK, but you can NOT mix the Bosch and DENSO/NTK.
If you Ask, Part store does carry NTK sensor.

 

Emissions systems problems may be bad news for car owners, but they are good news for mechanics. They certainly keep folks busy.

Our 2002 GC is back with the P0420. It's been on for awhile, but now the boss wants something done.

I looked at upstream and downstream voltages when fully warm and at low idle, 1/1 is bouncing like we would expect, and 1/2 is slowly fluctuating between about .70 and .76 V. Then if you bring the idle up at all, the 1/2 is fluctuating between as low as .3 and .6(ish) V.

From all that I have read, we need a cat. Is that correct?

 

It's baaaack... Last Spring we replaced the cat with an after market cat but not the sensors but it was running fine. Recently it has been throwing P0420 combined with a burning oil smell and oil out the exhaust. I looked at the sensors and #1 and #2 are mirroring themselves.

So, my bet is an oil leak dumping oil into the cat and clogging it.

One option is to remove the fire extinguisher make sure the drivers can run 100 yards while it burns to the ground. Probably not a good idea since we carry passengers.

Another option is to sell it and get another van.

Or we could find the oil leak and fix it. There are alot of problems with this van and it's at 290,000, so that may not be the best option. What I am looking for is suggestions on what may be wrong. Are valve seals failing common on these engines? If so, that's doable at a relatively low cost. I could do a compression test but I don't have a leak-down test kit - though they aren't too expensive. I could pull the plugs and see if they are oily, but if the exhaust seals are leaking, that wouldn't show on the plugs.

Suggestions on which one I should check first? Or suggestions on what else I should check?

Oh, I also know that this thing is a dog on power. No one likes to drive it because it's so slow. I'm thinking a Comp test is the first thing.

 

I'm betting both valve seals and rings.......grooves lined up or caked in from the oil burn.

 

Getting a look at the plugs, and doing the comp test seems like a good next step in any case. Just wondering though if and when you last changed the PCV valve? My '03 is the easy screw-in type, but I think your '05 has the "improved" PITA one. But if you're planning to remove the cowl to do the other stuff, at least the access to it becomes ok.

 

I drove the PO this morning and stopped at NAPA for a radiator cap and left it running. When I came out and started to give it some throttle, there was quite a cloud of oil smoke. It went away quickly. Just sitting through a stoplight for two minutes is enough to give quite a cloud when taking off.

I can do a torque converter stall in the parking lot and it wont spew smoke.

So does this help point to anything specific in your mind? Sitting idling it loads up the exhaust system, then it burns off when under load. Doesn't leave a constant trail of smoke.

 

Just accumulates more at idle, higher vacuum and whatnot. Remember the 3.0L in the late '80's - early '90's when they would drop the valve guide and the seals would fall off. You could see those smoke going down the road.

 

For the gurus of Spark Ignition:



Spark plugs. The one on the right looks good, but the white, ashy deposits on the one on the left is from oil burning off, right?

Here are the other four:



The ones on the left are the left side of the engine, the first picture are the ones on the front of the engine.

If I have it right that it's oil, Is this Toyota guy right:

Compression test will follow.

 

Front of engine

#2: 145 #1: 160
#4: 115 #3: 160
#5: 145 #5: 160

Mitchell tells me minimum of 100 Psi and 25% difference. 25% of 160 is 40 160-40=120. So #4 is low even after putting in a bit of oil.

The plugs are Autolight 5426 double platinum but #2 and #3 are now single platinum because the tit is gone from the strap and the gap is something like .065-.070 in. where the strap is burnt in a big arc. 63,000 miles on the plugs. But this won't cause these oil troubles, will it?

Do you think I need to look into the stem seals on the white, ashy plugs?