So i've been googling for hours searching some questions and not finding much to help me out. Tomorrow I'm going for an emissions test for my jeep. A few questions for you that have gone and passed. I know every state is different, (and California I hear is very strict) but I need some help. I've been on my states emission site and it wasn't much help.

If I'm buring/running rich will i most likely fail? For vehicles 1995 and older my state runs some sort of probe into my exhaust and tests the emission while the vehicle idles. They either let it idle OR they will run it on a machine of sorts at 15-25 mph's while the "probe" is in the exhaust. I doubt they will do the latter of the two as my jeep's lifted and has oversize tires? jeep's a 91 btw.

I've also read that if you idle rough you might fail...?

I just want my jeep to pass emissions, you've no idea how pissed I'd be if it failed..

I put this in the tech section because I figured my questions were tech related. Thanks for reading.

 

Without knowing what your states limits are it would be impossible to know,I live in ca,it is very strict. your car here needs to be running almost like new to pass. I would highly suggest if you have any issues that you correct them prior. Any miss will put out hydrocarbons hc,unburnt fuel. But how strict is your state.

 

Fill up with premium before you go.

Use some Sea foam as per the directions to get rid of dirty deposits [but no later than a couple days before the test].

Make sure your engines hot before the test, the cat works best when hot.

Change your oil right before the test [within a couple days] clean oil makes for clean emissions.

 

Michigan requires no emissions test; but i'd imagine giving your Jeep a very good tune up would be a good start. Make sure to change your spark plugs if they haven't been changed lately; air filter also. Wouldnt want to fail because of a 30$ tune up would you?