87 Renix 4.0 emission test results

I got this beast (87, 4.0, Wagoneer, 248,000 miles) emission inspected in one of the tough Texas counties (Houston) earlier this week.

Here are the results:

High Speed: 2441 RPM
HC (ppm) was 8 and the limit was 220 to pass the test
CO % 0.04 and the pass limit was 1.2 %
CO2 % was 14.9
NOx was 0.00 ppm WOW!!!!! :eyes:
O2 % was 5.1


at 698 RPM (Idle) low speed results were:

HC (ppm) 28 with the pass limit being 220
CO % was 0.13 % with the pass limit being 1.20 %
CO2 was 14.7 %
O2 was 5.4 %
NOx once again was 0.00 PPM :eyes:

Not bad for a 20 year old jeep with 248,000 miles on it.

I also found out that since it is a 4x4 they do not run the stress dyno tests, seems the 4 x 4's are exempt for some reason, says they can not test them like they do 2 wheel drive cars.

Any thoughts on the O2 %, it seems high to me?

Ecomike said:

I got this beast (87, 4.0, Wagoneer, 248,000 miles) emission inspected in one of the tough Texas counties (Houston) earlier this week.

Here are the results:

High Speed: 2441 RPM
HC (ppm) was 8 and the limit was 220 to pass the test
CO % 0.04 and the pass limit was 1.2 %
CO2 % was 14.9
NOx was 0.00 ppm WOW!!!!! :eyes:
O2 % was 5.1


at 698 RPM (Idle) low speed results were:

HC (ppm) 28 with the pass limit being 220
CO % was 0.13 % with the pass limit being 1.20 %
CO2 was 14.7 %
O2 was 5.4 %
NOx once again was 0.00 PPM :eyes:

Not bad for a 20 year old jeep with 248,000 miles on it.

I also found out that since it is a 4x4 they do not run the stress dyno tests, seems the 4 x 4's are exempt for some reason, says they can not test them like they do 2 wheel drive cars.

Any thoughts on the O2 %, it seems high to me?

Click to expand...

You're worried about O2? Why for? If CO or CO2 were elevated, I could see the worry - but I'd not worry about O2.

Doesn't a catalytic converter use reduction as part of its process? Seems to me that would end up liberating oxygen from other compounds (unless my memory fails, "reduction" reactions are the opposite of "oxidation" reactions, no?)

5-90 said:

You're worried about O2? Why for? If CO or CO2 were elevated, I could see the worry - but I'd not worry about O2.

Doesn't a catalytic converter use reduction as part of its process? Seems to me that would end up liberating oxygen from other compounds (unless my memory fails, "reduction" reactions are the opposite of "oxidation" reactions, no?)

Click to expand...

I am worried about the remaining O2 concentration's implications for the operating air to fuel ratio (i.e is it running lean).

The catalytic converter completes the oxidation process by catalytically letting remaining oxygen complete the oxidation of any remaining HCs and COs to CO2 and H2O. The actual catalytic step on the catalyst surface includes both oxidation and reduction. In other words the O2 is reduced and the CO and HCs are oxidized.

I learned a cool memory key from a substitute teacher once. It's OIL-RIG, Oxidation Is Loss and Reduction Is Gain, of electrons. In every Oxidation/Reduction reaction something is reduced and something else is oxidized. The oxidizer is reduced, and the reducing agent is oxidized.

For HCs plus O2, the O2 is the oxidizer and it is reduced, while the HCs are the reducing agent and they are oxidized.

Now try adding two oxidizers together that react violently and the terminology gets real fun!party1:

Ecomike said:

I learned a cool memory key from a substitute teacher once. It's OIL-RIG, Oxidation Is Loss and Reduction Is Gain, of electrons. In every Oxidation/Reduction reaction something is reduced and something else is oxidized. The oxidizer is reduced, and the reducing agent is oxidized.

Click to expand...

I was just about to mention the OIL-RIG. That's one of the few things I remember from high school chemistry, quite an enduring device for memorization.

Got mine done today in GA, 1987: 97,000 miles 4.0 AW-4

HC: 42/200
CO: .35/2.43
NOx: 0/2701
CO+CO2: 14.7/ 6.0 is min.

Go Renix:yelclap: