What Do These Smog Numbers Point To?

My '84 Toyota pickup with 155K miles failed smog check today. I'm sure the numbers tell a story of what's likely to need attention. But I don't speak the language. So, if you can interpret, I'd appreciate your adivce.

About the truck, It passed ok a year ago for change of ownership, and has been driven less than a thousand miles since then. Mostly ten mile trips to Home Depot on the weekend. In getting ready for the smog check, I changed the oil & air filter, scoped the ignition & replaced bad coil & wires, tested the EGR valve (blow & suck through it to confirm one way action). In retrospect, the temp guage has been running a little low. Maybe I should have changed the thermostat.

The numbers:

@15 MPH CO2 14.3%, O2 0.5%, HC 251 ppm, CO 0.43%, NO 1173 ppm @25 MPH CO2 14.8%, O2 0.1%, HC 126 ppm, CO 0.08%, NO 558 ppm

Since I can't see the numbers change as I adjust things like a mixture screw, a simple adjustment would cost me over $100. I'd rather spend the $100 on a new catalytic converter if that would do the trick. What do you think?

Thanks guys.

Reply to
Wekadog
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if I recall a cooler motor will run richer until it warms up.

Reply to
m6onz5a

Wekadog wrote in news:83f30327-358b-41a9-9dc2- snipped-for-privacy@d26g2000prn.googlegroups.com:

You're high across-the-board. Cat and O2-sensor were not hot enough, I'm guessing.

Book a test so you're the first one on the machine that morning. Take the truck for a half-hour drive--preferably at highway speeds--with all accessories on, including the A/C and rear-window defogger. Arrive at the test station exactly on time when they open. Do NOT let the truck idle, but shut it off while waiting.

Bet it passes.

Reply to
Tegger

All I had to do with my Supra was change the spark plugs...

Reply to
Hachiroku $B%O%A%m%/(B

high NO can be a symptom of excess combustion temperature. if the egr works correctly, typical candidates are too lean a mix, excessive deposits in the combustion chamber, etc. or it could just be a dying cat.

don't assume the egr is working right. it's not just a case of whether you're getting flow, but the /amount/ of it as well. suggest cleaning it to ensure flow rates are correct.

other than that, i'd replace the cat. none of your figures are that healthy - they don't last forever.

Reply to
jim beam

In getting ready for the smog

Make sure the egr *really* works... does it get vacuum when you 'blip' the throttle? Does the valve hold vacuum? Does the valve open when vacuum is applied? Does the RPM drop when the valve is open? Does it have air injection? If so make triple sure it works. Do you have the right spark plugs? (not platinum or anything fancy)? Tightening up the gap to the lower end of spec can HTH, Ben

Reply to
ben91932

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