Can't pass Texas emissions

East Texas TJ

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Apr 2, 2019
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East Texas
Hey all,
Well-maintained early model 1997 TJ 4.0 Sport with 107K Miles, which I purchased new. Other than a header and cold air intake, it’s totally stock and I’ve had no problems, besides that expected with the transmission. Use MOPAR parts if at all possible. It’s more of a third car which gets used on short trips around town.

--Emissions-- It’s always passed until recently. Last year (prior to emissions and it passed) I replaced the purge valve with a MOPAR part and did the best I could using an Autozone generic charcoal cylinder. No such luck this time. Chack engine light came on a few months back but it was running fine, so I blew it off.

After failing, I took it to a respectable local place which said:

1. The tank did not leak during the Smoke Test;
2. The new purge unit was not working (couldn't get it to open/close via electronic link to computer); and
3. There was a bit of fuel in the connector between the (hard) emissions line going forward paralleling the fuel line and the soft line coming from the tank.

So, they figured one of the emissions valves on top of the tank may be shot and fuel may be getting up the line and toasting the purge unit. However, I called Collins Bros who said they’ve never seen a tank like that go bad, unless it’s cracked.

Cant find a replacement tank (even used) anywhere and the line / emissions hose connector is no longer made.

Replaced the purge valve with a new MOPAR unit and the Check Engine light went out. Filled the tank, took it for a ride before retesting and the light came back on after 15 miles. Same deal.

Throwing a No. 33 code (An open or shorted condition detected in the duty cycle purge solenoid circuit. Mechanics are screeching their heads. (After $500.00~)

Any thoughts? Dr. Jerry, you still around?
 
The Duty Cycle Purge Solenoid looks like a pretty simple circuit. Do you have the service manual?

Positive comes from the fuse box (think its fuse 11 behind the glove compartment and ground comes from the PCM.

Personally, I would check for 12V+ on the positive side and reseat the PCM connector as a first pass. If not, you may want to start checking for frayed or broken wires. It could be that you have an intermittent connection that is causing the check engine light to come on after it looses connection or gets shorted.
 
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Also check the wires at the electrical connector at the purge valve. I had similar issue with the purge cycle not working correctly and throwing a code. I homed wiring between PCM and the purge valve. Everything ohmed good. Would hook it back up and it wouldn’t work. What I found was one wire was broken inside the insulation right at that connector. When I removed the connector to ohm out the wires, the broken one would make contact. Once I plugged the connector back in, the wire would open again because of the bend the wire had to make with the connector connected.
 
The Duty Cycle Purge Solenoid looks like a pretty simple circuit. Do you have the service manual?

Positive comes from the fuse box (think its fuse 11 behind the glove compartment and ground comes from the PCM.

Personally, I would check for 12V+ on the positive side and reseat the PCM connector as a first pass. If not, you may want to start checking for frayed or broken wires. It could be that you have an intermittent connection that is causing the check engine light to come on after it looses connection or gets shorted.


Hey,

You both were correct (in part). Thank you. Had an EE friend come over and take a look. The relevant socket portion of the PCC connector was oxidized and the connector for the purge unit was connected buy a thread. Easy fix.

However (laughing — kinda), now it’s throwing a No. 31 and didn’t pass again. Still no smoke leaking and the new purge unit works fine, at least pursuant to the mechanic’s computer.

As the A/C went out after the last emissions test (I’m not inclined to fix any time soon it as it’s not driven much.), it was suggested the Texas State Computer is simply reading codes misinterpreting “An open or shorted condition detected in the A/C clutch relay circuit” (which a Code No. 31 also indicates) as being an emissions issue. The fuse is fine. I keep reading a vehicle w/o an A/C unit will always put out a #31.

It’s such a simple system, the only other thing which makes even the slightest bit of sense (and was summarily disputed by Collins Brothers), is one of the emission valves on the top of the tank is shot. Of course, one can’t look at the valve w/o ruining the tank. When I suggested the computer was having issues, Collins replied only of it’s been submerged. Kind of hard to argue with those guys.

I’d prefer to fix, this but will get a waiver if necessary. (State employees tell me waivers may be thing of the past soon too.)

Thoughts? Any way to test the vales inside the top of the tank? Thanks again.
 
@East Texas TJ Fortunately, you are only 1 year (or less) away from being emissions exempt in Texas.

https://www.dps.texas.gov/rsd/vi/in...torcycles,two-year initial inspection sticker.

Have you checked your gas cap and/or charcoal canister? Quick internet search seems like those things have solved the issue for some.
Yep, new gas cap and new canister. The governor gave us a 2 month grace period for emissions, so I'm throwing in the towel and getting a Low Milage Waiver until it's permanently exempted. Probably keep trying too figure it out, however, I'm no longer under the gun.

Thanks for all your help.
 
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CONCLUSION: Culprit was a broken (worn out) passenger side roll-over valve on tank allowing fuel up the line which, in turn, toasted the electronic purge valve and the charcoal canister. Unfixable / unreplaceable / Tank no longer made / Junkyard tanks are all shot and a crapshoot at best.

After considerable research and phone time, the only aftermarket tank with emissions control and which exactly fits (and which is really expensive) is:

https://genright.com/products/jeep-tj-lj-extended-range-gas-tank-skid-plate-24-5-gal.html
 
Crazy outcome, and thanks for reporting back. That's a beautiful tank, but obviously is expensive. Might as well pony up for the aluminum skid for the +$100 at that price. Are you going to get it or just live with your existing tank?
 
Hey,

I’ll begrudgingly pony up sooner or later, but, in any case, before next year’s safety check. If I drive it more than 5K this year (which I will), it’ll be ineligible for another waiver. Further, Abbott (our gov) apparently just reinstituted the waiver program, so I’m thinking it could go away just as fast.

I’m now informed (contrary to that opined by Collins Brothers) this is a common issue with the tank. This leads me to think it was only made for a couple of years. However, I’m still kinda shocked it’s a relatively obscure issue.

The Jeep is otherwise in great condition, I bought it new right out of school and had hoped to keep it forever. Sooooo, I’ll be forced to patronize a California business~ :)

Next challenge is the adaptor which hooks the “hard” vapor line largely running the length of the vehicle to the soft lines coming from the tank. Yet another part which is worn out and leaking, but no longer made. Worst comes to worst, I can have that 3D printed tho.

Thanks for the help.
 
Hey, I found an OEM tank in great shape on Ebay. (Valves in good shape too.) Had it tested, then installed and smoked. No leaks. Reset the codes, filled it up, drove 50 miles and it passed. That evening, when I was taking the inspection paperwork to the grocery store to get my tags, the light and code came up again. WEV, my paperwork said I passed. That was last July and I've not bothered with it since. Since the TJ is now 25, it now only requires a safety check and not emissions next year.

All in all, I replaced every single part of the system except the two metal lines (which were inspected up, down and sideways), some twice, it still smells of gas and throws the code. Perhaps there is some sensor somewhere, but I think I replaced all those too. After spending so much money and time, I'm beyond caring. When auto prices come down, I'm going to get a Raptor 8-cyl, take this to Collins Brothers, tell them to gut it then repaint and rebuild.

It only has 106K on it and looks great. Have all sorts of people asking me if I want to sell it. Even with all the headaches it's recently given me — no way.
 
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I didnt know any of Texas had to deal with emissions testing. Learned something new.
 
Hey all,
Well-maintained early model 1997 TJ 4.0 Sport with 107K Miles, which I purchased new. Other than a header and cold air intake, it’s totally stock and I’ve had no problems, besides that expected with the transmission. Use MOPAR parts if at all possible. It’s more of a third car which gets used on short trips around town.

--Emissions-- It’s always passed until recently. Last year (prior to emissions and it passed) I replaced the purge valve with a MOPAR part and did the best I could using an Autozone generic charcoal cylinder. No such luck this time. Chack engine light came on a few months back but it was running fine, so I blew it off.

After failing, I took it to a respectable local place which said:

1. The tank did not leak during the Smoke Test;
2. The new purge unit was not working (couldn't get it to open/close via electronic link to computer); and
3. There was a bit of fuel in the connector between the (hard) emissions line going forward paralleling the fuel line and the soft line coming from the tank.

So, they figured one of the emissions valves on top of the tank may be shot and fuel may be getting up the line and toasting the purge unit. However, I called Collins Bros who said they’ve never seen a tank like that go bad, unless it’s cracked.

Cant find a replacement tank (even used) anywhere and the line / emissions hose connector is no longer made.

Replaced the purge valve with a new MOPAR unit and the Check Engine light went out. Filled the tank, took it for a ride before retesting and the light came back on after 15 miles. Same deal.

Throwing a No. 33 code (An open or shorted condition detected in the duty cycle purge solenoid circuit. Mechanics are screeching their heads. (After $500.00~)

Any thoughts? Dr. Jerry, you still around?
Emissions tests in TX? I lived there 45 years and never had an emissions test. Left two years ago. Is this something new? Local to your county only? I’m from Paris, TX, originally, but lived in other counties.
 
EDIT: didn't realize OP checked back in and said basically everything I said here. Nothing to see here, move along.

The OP was from 2020, but as of Jan 1 2022 '97s no longer have to pass emissions. Ask me how I know. You still need lights, seat belts, horn, decent tires, and a handful of other things, but they don't even plug in the reader and looking at the CEL is not part of the inspection.

Not all counties have emissions testing, but the populous ones do. Collin, Denton, Dallas country for sure. And you can probably get inspected out of county, but good luck taking that inspection to the tax office to actually get your registration sticker.
 
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EDIT: didn't realize OP checked back in and said basically everything I said here. Nothing to see here, move along.

The OP was from 2020, but as of Jan 1 2022 '97s no longer have to pass emissions. Ask me how I know. You still need lights, seat belts, horn, decent tires, and a handful of other things, but they don't even plug in the reader and looking at the CEL is not part of the inspection.

Not all counties have emissions testing, but the populous ones do. Collin, Denton, Dallas country for sure. And you can probably get inspected out of county, but good luck taking that inspection to the tax office to actually get your registration sticker.
Not all of the populous counties have emissions testing. San Antonio (7th largest city in USA) is in Bexar county and we do not have emissions testing. We are exempt due to our high air quality. Usually, once or twice a summer we will have an "ozone day" when emissions get high and there is no wind off the gulf. Everybody who can refrains from driving that day and the emissions drop back down into the green. Been doing that for at least 25 years here.