MoniqueTriana

Does anyone know what is the best gas to put in if your having a rich fuel problem? Im almost done getting the crap gas that was int here out- I have replaced most items like the hoses and spark plugs with OEM- runs better but want a little extra help before taking to emmisions. Anyone know of anything I can do? If I need to replace O2 sensor, where would that be? Upon research I've read that there is 2, then people say only 1. I have a 95 2 WD Cherokee 4.0 6 CY. Any help would be appreciated greatly.

Rogue4x4

Rich fuel has nothing to do with grade of gas, it has to do with the fuel/air mixture. Are you throwing codes on your CEL (check engine light)? If so, what are they? We need more info to help. Your vehicle will have a minimum of 2 02 sensors, if it's a California model, maybe more (unsure if your year would have more than 2, mine is a 97). The upstream 02 sensor is just after the exhaust header, the downstream just after the catalytic convertor. If you are mechanically inclined, both are fairly easy to replace, if they need to be.

MoniqueTriana

Thank you for your response. I live in Arizona and I think it has been registered here since it was new. I am mechanically inclined so I am sure that I am able to do it myself. I have no codes, no lights, and it drives great. After replacing all the items I stated the exhaust smell is a lot less than what it was. I checked all around the cat converter and I seen nothing resembling an O2 sensor. I just heard somewhere that there is an additive or a particular grade of gas that you can put in that can help reduce the rich fuel issue. I was thinking that it may be a fuel pressure sensor- but I read that if it was that the car would run badly, but it doesn't.

Rogue4x4

Well, if it runs fine, and it's not throwing any codes, what makes you think it's running rich? Just take it to emissions, you should pass just fine. I don't know how it works in your state, but they may have a "if it doesn't pass, you don't pay" policy. "Magic-in-a-Bottle" stuff is a fallacy. Good luck.

KingsColor

The O2 sensors are on the exhaust pipes, here are some pictures to help:



However, if the O2 sensors are ad, they would be throwing a CEL code.

MoniqueTriana

Thanks. Its failed emmisions 4 times due to Hydrocarbons and Co2- Ive done all I can but afraid to take it back.

Rogue4x4

See, this is info we need. Do you happen to have the data sheets with all the numbers? Maybe your CEL bulb is out...Any and all data you can provide will net better results.

EDIT: Here is some reading you can do to better explain the issues you're having, and what you might want to look at next.
http://www.916smog.com/smog-help.html
Scroll down to where it says general background and read from there...

MoniqueTriana

OK Thanks, heres the back story:

It sat for a while because I had a baby and didnt drive it- Took it to emmisions and pass everything but pressure test. Found out it had a crack in tank by nozzle. Had tank replaced. HC, Nitrogen and CO2 were very low in this testing. Took back with new tank, passed pressure test, but failed NOX. Reading before tank was .98 woth a 3.0 standard. Now is 5.146. HC passed but barely, went from .34 out of 1.6 standard to 1.36. CO2 went from 3.15 out of 20 standard to 8.27. So the NOX is the issue here. The exhaust did smell bad. I replaced the plugs with OEN Champion copper, new cap adn rotor and all hoses whether they needed it or not, some were cracked yes and I'm sure that was an issue. Im not sure if what I did may have fixed the issue.

Rogue4x4

Did you also replace spark plug wires?

MoniqueTriana

No they were fairly new and still in good condition, got them a few years ago and only had about 5K miles on them.

Rogue4x4

Just because they are newish, doesn't mean they cant be bad...when pulling them out, if not done carefully, they can be damaged...best to test them with an ohm meter before re-installing to be sure, don't know if this was done or not, but lets give it the benefit of the doubt and say they were good. So, if you were running rich before, new cap, rotor, and plugs may have solved the running rich issue, with the improved spark. High NOX readings, however are usually associated with running lean, have you checked any of your intake, like the air filter/intake for leaks or holes, or replaced the air filter? Anything replaced in the emissions (egr valve, catalytic convertor, etc?)

DFlintstone

95 still have the MAP mounted up on the firewall? ;

There is a brittle little tube. It comes out of a rubber plug, low on the engine side of the throttle body. It runs back to the firewall, then up to your MAP sensor sort of high up there near center on the firewall. CRUCIAL!! The MAP will tell the ECU to dump fuel with less/no vacuum. Any crack or blockage and it will be pig-rich.

I think the rear 02 sensor only monitors the Cat, it's the front that matters. If you don't know the age/miles on yours you might want to change it. Especially with high HC. (they may fail rich). Since any MPG improvement will pay for it, not a bad idea.

You might have fixed it if you changed the MAP tube. That is a supper important deal there.

Also any little miss will peg the HC...Good luck!

BlueRidgeMark

First thing to do, is get over the "magic in a bottle" thinking. It's not helpful.

You have a solvable problem. It just needs systematic troubleshooting.

salad

^^^^^^ very important!

Also your spark plugs, did you use Champion coppers and verified the gap was set to 0.035"?

DFlintstone

Comon' SALID! I know the air is thinner up there....(I haven't tried the "OES's Though)

Anyway great point on double checking the gap. Monique, always smart to check what was in the box. Did you? It might have been dropped, or they might not be at .035 for some other reason.

In a bind with HC, stick a new CAT in it, and go directly to the smog shop, preferably across the street. As long as it has fresh fuel, (no harm with premium), An additive might be more likely to hurt than help, in my opinion.