How can I check the current O2 to see what it's reading?

Also, who makes the OEM sensor? Denso?

>>>*KInda what I was expecting with the CO reading high, glad it's solved as far as the tests are concerned, but now I have a concern.

If the system is running rich for some reason, power/economy will be less than it could be, and you will eat cats fairly fast, too.

Sometimes I wish I had taken the time to get into the systems controls for these engines, but I must concede that is my weak link.

Even when running dyno testing I stayed out of the way and let the tech team do their thing.

I would be suspicious that my peers here might be onto something, the computer can only react to the information is recieves, of course.

Your experience has given this old man a wealth of info to pass on to others, so thanks!

Please followup post as you go through the systems, I will be curious if it does turn out to be a simple sensor concern....*EB

I got the truck back and I have some test results. They conflict a little with what I was told over the phone. I'll comment after the resuls.

The first number is at 15mph (~1850rpm) and the second is at 25mph (~2047rpm) on the dyno. I also typed out the reported average emissions for passing vehicles.

Test 1 :270 cam, old cat
HC(PPM): 206/225 avg43/32
CO(%): .63/.62 avg.16/.15
NO(PPM): 719/725 avg406/349

Test 2: stock cam, old cat
HC(PPM): 198/181 avg43/32
CO(%): .64/.60 avg.16/.15
NO(PPM): 934/815 avg406/349

Test 3: stock cam, new cat
HC(PPM): 35/18 avg43/32
CO(%): .03/.01 avg.16/.15
NO(PPM): 25/16 avg406/349

From test 1 to test 2, it looks like swapping to the stock cam slightly decreased HC levels. The NOx levels, however, increased. Am I correct that by reducing HCs (unburnt fuel), the exhaust temps probably went up slightly, which caused the increase in NOx? Am I also correct in saying that the changes between test 1 and 2 are subtle and the 270 cam does not significantly affect emissions?

From test 2 to test 3, you can see the new cat cured the tailpipe emissions. I don't even know if I can believe the last numbers they cranked out with the new cat. Is a catalytic converter really that much of a miracle worker?

Based on how broken up the old cat was, I imagine test 2 reasonably represents the exhaust upstream of the catalytic converter. Does this seam high for out-of-the-engine emissions or is this normal for precat exhaust emissions?

I don't want to melt down another cat so please let me know if you think I should persist in finding the real problem.

Yes Cat converters are amazing things. I read once that is we had platinum coated radiators, we would be cleaning the air more than poluting it. This is why it is important for even us tinkering folks to keep cats on.

Running wihtout a Cat is like running 20 cars with cats.

Go to http://www.sparkplugs.com and order up a Denso sensor. Should be less than 40 bucks, and when I did the one on my 87, it was identical to the one I took off.

If you will post up (or pm me) with all the readings provided (CO2, O2, HC, CO, NOx) I'll calculate how rich or lean the truck is running. It's called Lambda and it's been a valuable bit of information for me when diagnosing failed smogs.

Also, on the 1 non-catalyst car equals 20 catalyst cars ont he road, the guy in the stall next to me at work (GM dealership) smogged an 86 Suburban 4x4 with a 7.4l big block, carburated, non-catalyst. It was putting out far less than the Toyota in this thread.

Remember, that's carburated and without a cat converter at all!!!

I just stared at the paper and blinked a few times. It just didn't make sense.

52degrees, thanks for the idea! I tried out some numbers using this online calculator http://www.smogsite.com/calculators.html#lambda

I plugged everything into the calculator and here are the Lambda values I got from the smog checks mentioned above along with the complete smog data.

EMISSIONS CHECK SUMMARY (15mph/25mph)

Test 1 :270 cam, old cat
HC(PPM): 206/225 avg43/32 [color:"red"]FAIL HCs[/color]
CO(%): .63/.62 avg.16/.15
NO(PPM): 719/725 avg406/349
CO2(%): 13.8/13.8
O2(%): 1.0/1.0
Lambda: 1.021/1.020

Test 2: stock cam, old cat
HC(PPM): 198/181 avg43/32 [color:"red"]FAIL HCs[/color]
CO(%): .64/.60 avg.16/.15
NO(PPM): 934/815 avg406/349
CO2(%): 13.6/13.6
O2(%): 1.1/1.1
Lambda: 1.026/1.028

Test 3: stock cam, new cat
HC(PPM): 35/18 avg43/32
CO(%): .03/.01 avg.16/.15
NO(PPM): 25/16 avg406/349
CO2(%): 14.3/14.3
O2(%): 0.8/0.8
Lambda: 1.035/1.037

So it appears the engine is running on the lean side, but I don't know how to interpret the magnitude of leanness.

Please let me know where you think I should go from here.

Unless you are an automotive engineer, it'e difficult to judge two differernt engine systems against each other. There are hundreds of variables involved with the emmissions produced by an engine. If the engineers assumeed the engine would have a cat in the exhaust, they cen take liberties with other design areas that they would *not* take in a non-cat engine.

If your vehicle was designed to have a cat & you take it out, you are no better than those folks who leave their lunch trash on the trail for others to deal with, IMHO.

Dave

I'm on your side Davepet <img src="/forums/images/graemlins/patriot.gif" alt="" />

I agree with what you are saying for the most part. Cat converters make a big difference overall in the reduction of emission.

I was really just trying to show a bazaar example that I saw just that day.

I've also had Corvettes that would have failed smog with the cat converters removed and the O2 sensors disconnected, but they didn't fail by much. That suprised me too.

If I seemed to be argumentative with my statement about the carbureted, non-catalyst Suburban polluting less than the Toyota here, that was not my intention. I was just suprised and amazed and wanted to share. It bore no relevance. BTW, that truck failed the visual inspection even though it passed everything else, and the cut-points and averages were way higher than what we saw out of it. Like I said, just a weird thing worth mentioning, but with no real relevance to the topic at hand.