Failed emissions for the 2nd time

Ok I'm getting a little frustrated now with the Jeep I just replaced the O2 sensor and changed the oil yesterday, on top of a full tune up, a tank of techron, a new 195 t-stat, new cat/exaust and I am still failing.. The first in the list is my numbers and the second is state requirements:

HC 2.13 gpm......................1.60 gpm
CO 78.03 gpm....................40.00 gpm
NOx 1.18 gpm.....................2.50 gpm

Here are the numbers from my first test:

HC 4.27 gpm
CO 91.21 gpm
NOx 2.07 gpm

The numbers have come down but I still have extremely hi CO. I had the engine nice and hot before the test but did't seem to help too much. I'm at the point of taking it to the mechanic and let the pro handle it. Any other suggestions???

Thanks

Yes, it time for professional help. Don't want to be throwing parts at the vehicle on a guess. This is where hooking up the vehicle to the test set will pay big rewards. The mechanic can see how the engine is performing, how long the injectors are open, etc.

I had a coworker who failed emissions similar to you. He took it in to the mechanic because he could not figure it out. The mechanic installed a new cap, rotor and wires. That solved the problem. You did not say how many miles on those items. My owner's manual say 30K for plugs, 50K for the other items.

The fuel/air ratio is controlled by the MAP sensor, TPS, coolant temp, manifold air temp, and oxygen sensor. These tell the computer and it opens the injectors for the specified period of time.

It could be an ERG not operating or malfucntion. If it sticks open then you will get bad MPG, I learned this the hard way.

Find a mechanic that understands Renix XJs and let him loose.

I do not know how many retests you get but you may want to change cap, rotor, wires and plugs. Pick all of them up at your dealer, they are priced resonable. Also dealer parts "have to work" by law, aftermarket parts should work but are not required to by law. That may fix you problem and avoid the mechanic otherwise you can do nothing more and let the mechanic figure it out.

Martin thanks for the reply. I purchased the cap, rotor, plugs, wires, 195 tstat, housing, coolant bottle, hoses, tps, and O2 sensor all from the dealer and all less then 1 month old. Oouch... Anyway thats why this is getting really frustating and to boot I boiled over when the emissions test was over And I changed all that stuff!Sometimes I feel like I should leave well enough alone...

Sounds like time for a new CAT. After failing my emissions test due to high nox I tested my egr and discovered a bad egr solenoid. Your nox does not seem to be the prob however. I did call the state police office incharge of emissions testing in my area and the tech there was very helpful in pointing me in the right direction. I also changed the cat due to the milage and o2 sensor. After taking off the old cat w. about 80,000 miles we looked through one end to the other into a light and discover half the cells were clogged. Got a new direct fit cat from www.mufflertech.com for about $60 delivered and had meinike install it for $50. Good Luck. Greg

Greg Smith said:

Sounds like time for a new CAT.

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I had the CAT replaced a little over a month ago.

I stopped by the dealer this morning and ran down my current problem to the parts guy who has been helpful up to this point. He suggested before bringing it in and getting overcharged, pickup a vacuum tester and test the system pressure for leaks. He said vacuum leaks can cause emissions hell. So hopefully I find some sort of vacuum problem which will make me feel a little better.

Possible quick fix. I have had numerous problems with failing these wonderous inspections. I have always changed the oil dont know why just found it helps and ran a can of the "guaranteed to pass" stuff. You put a bottle in a full tank and run the tank out. I would say this has worked for me roughly five times without failing. Good luck and remeber this is would only be a short term fix.

Possible solution?...

I'm a newbie, so take that into consideration. But, I was curious if your Jeep has bigger than stock tires with stock gears? If this is true I heard when they do the emissions test the engine will run at higher rpm's making higher numbers on the machine do to the offset made by bigger tires and stock gears. So to fix this put back on the stock tires and it will read lower numbers on the machine since the tire size and gear ratio will match. Just a suggestion, hope things work out. If I'm wrong somebody please clarify things for me.
Later,
Chad

mudhound32 said:

....I boiled over when the emissions test was over...

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I think this may be your problem, or related directly to it.

1. The ECM gets signals for richness from two prime sensors: O2 and temp.

2. There is NO reason for you to have boiled over, other than something being wrong in the cooling system.

3. If you were running hot, the ECM would sense this and enrichen the mixture (to avoid burning exhaust valves from a lean mixture).
Your test results indicate that the ECM is doing exactly this (hi HC & CO + low NOx = rich).

4. Solve the present overheating problem, and I think you'll solve the emissions problem.

Is the system throwing any codes?

-Rick

i used to work for the maryland emissions, and i know how to get them to pass under maryland standards. take about an hour or hour and half before your test and drive around. try to get the exhaust as hot as possible. do about 30 mins hway and 45 city. while stopped, redline it a couple times.
its worth a try?

Rule of thumb;

CO to much fuel or/and not enough air.

You can check the O2 sensors by hooking up a scanner or volt meter and watching the voltage. A bad O2 that reads lean would tell the ECM to add more fuel. Check fuel pressure, to high of pressure will make the inj to add to much fuel to low and it won't add enough. If it a 96 or newer you should think about a OBD II scanner. You don't need to get a top of the line one but get one that allows you to see the values of the sensors. I use a Snap-On scanner in my job (smog tech) and it does save me time. I can look at a O2,TPS and other sensors without getting out of the car/truck.

go to the grocery store buy 6quarts of rubbing alcohol and dump it in the tank you should pass then!

BiggerIsBetter said:

I'm a newbie, so take that into consideration. But, I was curious if your Jeep has bigger than stock tires with stock gears? If this is true I heard when they do the emissions test the engine will run at higher rpm's making higher numbers on the machine do to the offset made by bigger tires and stock gears. So to fix this put back on the stock tires and it will read lower numbers on the machine since the tire size and gear ratio will match. Just a suggestion, hope things work out. If I'm wrong somebody please clarify things for me.
Later,
Chad

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well, i dont exactly know how they test emiisions other places, but it doesnt really make sense that tires would have anything to do with emissions. they would just attach the hose to your tailpipe and then rev the engine to whatever rpm....the tach shouldnt be affected by the tire size.

Çrestfa||en said:

go to the grocery store buy 6quarts of rubbing alcohol and dump it in the tank you should pass then!

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Don't do this. It's the same as dumping 6 quarts of water in the tank along with a little alcohol. Read the label on the bottle and you'll see. You can use alcohol to disolve the water already in there but you want alcohol that is 90+% alcohol.

The MAP can play a role in too rich of a mixture. If your vacuum line to the MAP sensor is leaking, you'll be running rich.

Also check your temp sensor at the rear of the head next to the valve cover, if it's bad it will not give the correct reading to the computer causing the engine to run rich-computer thinks it's still cold. The sensor at the water pump is for the temp guage only.

emissions

I'm new to the board but I have a 89 with a 4.0 that has just failed for the 2nd time as well. It passed the readings at idle but when tested at higher rpm's it was over for HC, CO and NOx. There are a lot of suggestions about vaccum leaks in this thread and was wondering if anyone knows if this could be the cause of the problems that I'm having as well.