Need to pass emissions test

Somebody ripped off my Catalytic converter on my truck and I replaced it with one of those cheap Chinese universal ceramic converters.

I'm not sure if it will pass. The engine is a 4.0L I-6.

Should I bother putting in some premium gas?

What about adding some Seafoam to the gas tank? Or would that make it worse by breaking up carbon?

None of that will do anyhing see if it passes, what else would you do? Was the cat epa certified?

If the check engine light is not on, run it thru the test and see what happens...:uhoh:

This sounds like an older Jeep. It sure helps us if you state the make, model and year.

For example:
If the check engine light is not on, run it thru the test and see what happens...:uhoh:
As Blt says, if your car is 1995 or newer, it has OBDII, so the functioning of the cat is, in part, monitired by the ECM, so a malfunctioning cat may likely result in a check engine light. Pre-'95 vehicles often do not produce a check engine light when the cat is bad.

IMO change the engine oil and filter, make sure the air filter is clean, make sure the engine and cat are fully warmed-up when you do the test, and go for it.

It's a 92 Jeep Cherokee, and I got one of these cheap Marmont cats from Autozone.

I got one of these cheap Marmont cats from Autozone.

Your lucky your not in California (or maybe not so lucky :cool:), those would not pass smog here with the new smog laws. :runaround:

In Ny Pre 95 cars do not get tailpipe tested, only the NYC area.

In Cuyahoga county they should check the light on 1996 , and for 1995-1986 should run it on the rollers. You can also tell them it is full time 4wd and they will not roller it. It is free anyways, try it and see if it passes.

Replacement cats should be warranted against defects and have to be certified for sale, so you should be fine getting tested. At worst, you pay your money, it fails, you get it replaced with a good one, and the re-test is usually free within a certain time.

In Cuyahoga county they should check the light on 1996 , and for 1995-1986 should run it on the rollers. You can also tell them it is full time 4wd and they will not roller it. It is free anyways, try it and see if it passes.

How would I be able to get away with that? All they have to do is look in the truck and see its not full time 4wd.

I'm wondering If the auto parts store would accept the return of a Catalytic converter.

Sounds like you're getting ahead of yourself...or as some people call it "advance planning". Have the test done first, then worry about any problems if they arise. Besides, if you do happen to fail, you can show that the OBD is working and the proof of the recently installed cat...they may grant a waiver or allow a retest.

If you are pre-1996, then the only way the "check engine" light will come on for an exhaust issue will be for a faulty or abnormal reading (i.e. too rich or too lean) from the upstream O2 sensor, there are no O2 sensors after the cat.

As far as returning the cat if need be, check your receipt. The terms are usually printed right there for warranted items.

Should I drive around a while with the new cat on before I get the emissions test? Would there be any problems if I put it on right before the test?

OBD I system is usually a visual inspection for a catalytic converter.
Take your car in for the inspection, after reaching normal operating temp.

I see no reason to wait for the cat to "break in". If you are coming due for testing soon, then just go and do it. Again, if something does fail, you have the proof of purhcase and qualified install. But it won't hurt if you let it go through a few heat cycles to allow any volatiles left over from the manufacturing process to be burned off. A week's worth of driving should be plenty of time for that.

I can tell you from experience that any new catalytic converter, no matter how cheap, will get a vehicle through emissions testing immediately after installation, unless something else is wrong that causes it to fail. Subsequent years are a different story. I bought a cheap one once, and it only got me through 2 years before I had to put the right one on it. The sooner after installation it is tested, the lower your NOx reading will be. Just drive it on a highway for at least 15 minutes before pulling in to the test facility. Don't add anything to the gas, and don't use premium. My ride failed a tailpipe emissions test once with premium, then a week later with midgrade, then passed a week later on regular, with no repairs or adjustments. If your oil needs to be changed soon, do it before the test.