Hi Folks...I hope can get a little good advice. I've got a 89 4dr Montero with 3.0V6, Auto & 154k. This week it failed smog in a big way...HC were high, but NO was through the roof!
Here's the test results
15mph 1699rpm
%co2|%o2|HCMax|HCMeas|COMax|COmeas|NOMax|NOMeas
14.0|1.2|102 |102 |0.47 |0.02 |879 |2081
25mph 1774rpm
%co2|%o2|HCMax|HCMeas|COMax|COmeas|NOMax|NOMeas
14.0|1.2|69 |78 |0.61 |0.02 |661 |1474

EGR appears to be working.
Any ideas based on the readings? Unlike some of the other high NO requests, I'm curious about the the high HC levels as well.

Anyhow...thanks in advance for your help!
Scott

I don't have any definitive answers, Scott, but here's a couple of thoughts. When you say the EGR appears to be working what are you basing that on? I'm wondering if some of the passages in the intake plenum may be clogged up.

For my '89, when it originally failed smog 4 years ago the replacement of the O2 sensor was enough to let it squeak by. When it failed 2 years ago I had to replace the catalytic converter as well as do the valve stem seals to deal with "visible smoke from the tailpipe". This year I was wondering how it would fail, but it passed with some really good numbers, so the cat replacement seems to be holding up.

That's about the sum total of my smog knowledge -- I know there's some really smart people on here regarding this stuff and hopefully they'll chime in. California sure doesn't make it easy to hang on to our perfectly good older vehicles <img src="/forums/images/graemlins/zombie.gif" alt="" />

Eric W.

Using the Lambda calculator: http://www.smogsite.com/calculators.html

Here's your air/fuel ratios:

15 mph AND 25 mph: 15.54 Air/Fuel ratio, Lambda 1.057

"Lambda too lean 1.02 and above - reduction less effective (Nox high from CAT)
Lambda > 1.02 = Reduction (cleaning up NOx) Less efficient"


For the lean condition, test the O2 sensor response time, Coolant and air temp sensor readings are correct, the MAP/Baro and the mass airflow sensor are within calibration. Also verify that you don't have any misfires, which will put more O2 into the exhaust, also.

For High NOX: Verify EGR operation and flow, the ignition timing is correct, NO exhaust leaks upstream of the cat-converter, and that it is not overheating before condeming the cat-converter.

That's a really informative site! <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/kewl.gif" alt="" />

Eric W.

Do the EGR operation check as outlines in the FSM to ensure your EGR valve is working vacuum lines are good to go and hooked up correctly. Then clean the EGR ports in the plenumn. Also make sure the EGR pipe is good to go. A leaky pipe has caused me to fail in the past...Also a Seafoam treatment can help get rid of some carbon in the combustion chambers, which could contribute to higher NOX as well. My 2 Cents..

The static timing? My Raider was 3 degrees advanced and greatly affected the NO reading, took care of retarding it and fixed the NO.