Stephon

Help!!
I've bought a Cherokee and now my wife won't let me sleep in my own bed.

So I've been battling with my new to me XJ, I just failed emissions for the fourth time. The past three times I didn't have any emissions systems hooked up (egr, ccv, charcoal canister). So over the weekend I started reading up on all the posts and threads I could. I did my best to hook up all the hoses and fittings that I have read about here in the Cherokee forum, but apparently the nice people at the Arizona emissions think I should keep learning about what I've got under the hood.

About my XJ it's a '89 with a '95 4.0 it's been pieced together between this Cherokee and the '95 I believe the fuel rail and possibly the intake manifold are from the older '89. I'll include some pictures of what it looks like under the hood.









Here is a picture of my results from about an hour ago, I crumpled them in disgust



Oh I almost forgot, I put a new catalytic converter last week, I stopped by the "guaranteed pass" emissions mechanic next door, after failing the third time, all he wanted to do was sell me a brand new cat saying that I most likely burnt it out with in the first two days of having it, I'm thinking they make their money form the catalytic converter manufacturer.

Well friends any help would be great.

Thanks,
-The XJ newbie Stephon

FL Denmark

no 1 reason for high nox is to high temp within the combustion chamber.
and reasons for that could very well be a mixture to lean. therefor check all you vacumtubes, check for vacum leaks at the manifold.

another reason could be bad timing or bad sparkplugs.

also make sure the cat is really hot.

good luck with it

BuckB91XJ

You definitely have the old RENIX style throttle body and intake. I'd say pretty much all you have there in your Jeep from the 95 is the short block and possibly the head. Looks like all of the vacuum plumbing and emissions stuff from the old style as well.

BuckB91XJ

I saw the EGR valve there in the picture (below the throttle body under side of intake manifold). It looks to be in desent shape but, I can't tell from the pic if it is hooked up.

CharlesS

Since you implied that a lot of the emissions equipment are disconnected then I would verify the EGR is functioning properly. In the picture it appears that the vacuum lines are connected.... The EGR (Exhaust Gas Recirculation) valve controls the entering of exhaust in the the combustion chamber which lowers the combustion chamber temperature and lowers emissions...

Stephon

How can I check to see if the egr is functioning properly? I will take a better picture of it and post later today

413maxwedge

You need to get yourself a manual for your jeep like a chiltons or better yet a fsm,I bought a FSM on ebay for 29.99 shipped all 4 books for a 2000 xj.

cruiser54

Is your O2 sensor installed on the exhaust manifold, and if it its, how old is it?

I think your Jeep would most likely pass emissions with a non functioning EGR. That said, how do we know if your EGR pintle is fully seated. If it's not, you will geat an impossible to detect vacuum leak. Might remove it and make sure it is sealing properly internally.

Stephon

The o2 sensor is on the exhaust but I know the previous owner liked to forge streams so it could be shot. He was kind enough to load me to the gills with extra parts when I first drove it home, I'm pretty sure I saw an extra o2 sensor in there. How does the o2 sensor effect the emmisions?

DFlintstone

I believe the o2 sensor tells the computer how much fuel to inject. A few things:

*Once mine would not pass until the day I left him alone with it. (nobody was there to see which pipe his sensor went into).

*I have herd of going DIRECTLY to smog after a new cat. The "virgin" is reported to have extra benefits. (I wouldn't personally know)

* The purpose of the EGR is to reduce Nox. Not to disagree with cruser but "smog" might want to see that it's hooked up and working. You should see the rod move when vacuum is applied. (don't put a BB in the vacuum line after it's smogged. Then it will only LOOK like it's in and working)

cruiser54

Have the EGR hooked up for sure, but it would probably pass without it "working".
The O2 sensor sends a signal to the ECU so that it can adjust injector pulse width to maintain a 14.7 to 1 air fuel ratio. VERY important!!!

Stephon

Today I went and bought a haynes manual, I've been going through the emissions chapter and came across this

on my motor the EGR tube is pinched off at the entrance of the motor



and at the exhaust pipe



am I correct in assuming that since my motor can not recirculate any of the fuel rich exhaust fumes back in to the motor, then I will have higher NOx levels?

cruiser54

Not really. Test the O2 sensor. A Renix should pass emissions without an EGR.

DFlintstone

I would agree with cruiser, he knows his stuff. The EGR works by F%ing up combustion. Supper high pressure and temps over 3000* is where NOx forms. With exhaust in the mix things don't burn that well.

last century when I had a smog license, the EGR would not function unless you where in high gear. Tough to do in a shop. Don't know about now. Since you at least need it to look like it's hooked up, and you got good advice to remove it and check to see it's free and seating, maybe you should go ahead and make it right. Might save you some headache, and hey, you'll be making less smog. You can always "loose a BB" after.

Stephon

Well some how they already gave me the green light on the visual inspection, I'm only failing because of the high NOx levels. I was thinking since the system wasn't recirculating the exhaust that it was causing the high NOx.