brusso1989

everything is good to go for emissions on my 89 jeep Cherokee except the carbon monoxide level. I have to be at 25 and out of the 4 times I went I'm at 26 average. plugs and wires are good, map sensor is good, tps is good and in tune, fixed small vacuum leaks and the oxygen sensor is only about 2 years old. I am running without a thermostat right now but when I do the emissions test I make sure I'm at 190 running temp. would my older renix engine have a "open circuit" causing me to run rich without a thermostat even though I let it heat up to 190 when I go to the test? another idea is I bypassed the ballast resistor for the fuel pump about a year ago and it runs pretty good but could bypassing it cause it to run lean? those are really the only two things I can think out that are left that could be my problem. any input would be great!

bryanintowson

What kind of shape is your catalytic converter in?

t.mcginley.jr

High CO means its running rich, not lean. Either it thinks its too cold because of no thermostat (or a bad coolant temp sensor), or whatever bypass you did on the fuel pump is causing pressure to be too high and you're dumping too much fuel. Could also be silly things like an old dirty air filter, dirty throttle body, or a ****ty brand of O2 sensor. Clogged cat is a possibility too but usually you will have high NOx emissions too with that.

Bugout4x4

You might be on the right track. It might indeed run cleaner at the proper higher operating temp it was designed to run at. Operating temp also affects how efficient the convertor does it's job.

brusso1989

Cat is brand new. I'm gonna put a thermostat in it, new coolant sensor and if I can find a ballast resistor for the fuel pump then that too. But wouldn't it not run rich with no stat as long as it warmed up to operating temp before it ran through emissions?

Bugout4x4

I don't think it is so much that you are squirting richer, it is more likely just not burning as efficiently. Emissions are why a lot of new cars run at such a high temp out of the box. Mine is normal at 210 so yours is operating way under normal combustion efficiency. And like mentioned, the temp of the Cat makes a huge difference in how well the catalyst is doing it's job. It requires it's own internal operating temperature too

quneur

CCV/PCV line clear? We used to put very little gas in the tank and then use a few bottles of fuel injection cleaner. Then after the inspection, fill the tank up with gas.

cruiser54

Click on the link below and do Tips 1,3,4, and 5.

cruiser54

Pressure is regulated by the fuel pressure regulator whether the resistor is there or not.

Brand of O2 sensor could be it also. As could loose intake manifold bolts causing low vacuum to the MAP sensor.

By all means, he needs a 195* stat.

DFlintstone

Agreed with Cruiser, get a 195* T-stat. (any T-stat will be fully open before it overheats.

If you add a resistor all that will do is quiet the pump a bit and maybe make it last a little longer. Pressure is regulated by the regulator.

I wouldn't add anything, just run premium. The Chevron with techron would be my choice for the test.