motobro

I am rebuilding a 95 runner with 139 k on the odometer using a motor from a 91. I have swapped all the appropriate intake and plenum and all that stuff, it runs great, idle is a little high. I took it to get it smogged and I have failed the NOX portion of the test.
Here are my results.
HC@ 15mph- max-88 meas-12
@ 25mph- max-53 meas-11
CO@15mph- max-.64 meas-.03
@ 25mph-max-.77 meas-.04
NOX@15mph-max-508 meas-1190
@ 25mph-max-761 meas-856
So in researching alot of threads here I think i need to clean and test the egr system. I also wonder if the cat is bad ? The exhaust note is a little deeper than the 94 4runner that I have, it (the one that failed)also runs very crisply with a lot of power. So this makes me think that the cat is bad. Also from the readings My nox is lower at 25mph. I have read here that the EGR valve does not function at or near idle (is this true?) This makes me think that at 25mph the egr valve works but the cat is not catching any NOX ? There are no check engine lights and the timing is set at 11 BTDC.
So In attempt to fix I will:
1- test/clean the egr system.
2- tap on the cat with a wrench and compare it to my 94 to see if it sounds hollow in comparison.
3- retard the timing to 8%, they check this in the test if its too low they fail you.
4- Siphon the gas and replace, its about a year old if not more.
5-Replace PCV vale

Any body else got any suggestions ??????????/

motobro

I took the air plenum off, I found that I had forgotten two of the bolts on the plenum nearest the carb and in between the two nuts at either end of the plenum. I changed the PCV, I don't think it was bad but anew one wasn't that much. I cleaned the egr system the best I could, it did not really look dirty. I siphoned most of the gas out and retarded the timing to 7%. I ran out of time so I did not test the egr system.
I tapped on the catalytic converter, but could not notice any thing odd. Its got a heat shield around it so the tapping can only be done on the ends.
I think my problem was the missing bolts on the plenum, I was getting kind of a whistling sound after it warmed up and the idle would shoot up to 2k. This was gone after I reinstalled the plenum and started it. I have read in another post that lean condition in the fuel system can lead to higher NOX readings. That might explain why the 15mph reading was so high, it was sucking air into the intake from the poorly sealed air plenum rather than through the air intake. Only a trip back to the smog guy will tell.
On a different note, I have a 92 4runner at a local RV storage yard that I use for parts, I was there getting a door handle from it. All this talk of catalytic converters led me to look under the truck at the cat. It was gone, some tweeker had stole it !!!!!!. there were 4 bolts on the gravel along with a clamp.