stew

Hope someone has sugestions before I start replacing parts.Tech.said possible exhaust leak,maybe O2 sensor.
Jeep runs perfect,decent gas mileage.94 sport,213K,well maintained driver.Upgraded to 703 injectors,bored throttle,replaced exhaust header,muffler and intake gasket after smog in 2011.
Top pic is 2011,lower is today.Thanks.

highmileage

Take a look at your exhaust manifold they can and do crack and will cause your HC#s' to get really high. The crack causes you to have a run rich problem because the O2 sensor is showing lean due to the crack. Do replace your O2 sensor.
Also on my page I have multiple threads on smog issues, might want to look at those for some help.

MonacaYankee

Wow those are some low NOx values allowed. My 94 passed with over 600 on each with 1014 allowed. It failed the first time 1144. After it failed I seafoamed it through the brake booster line. I don't know if that actually did something though. My tank was half 8 month old gas which might have had something to do with it.

When was the last time you did a tune up?

stew

Thanks,great tips there.https://www.cherokeeforum.com/f2/gro...r-help-130897/
Repaired(welded)small exh.manifold crack after first test 2 years ago.Ill try the smoke test.
O2 sensor looks to be OE,cat looks fairly fresh judging by welds.Zero drivablity issues.Runs great,but does use 2 qts. between 5K oil changes.
Don't have temp gun to check cat delta,ill have to take to muffler man.
Usual valve train clatter.Would burnt exh. valve cause high NOx readings?
Maybe compression test,vac reading is needed...

highmileage

I have also found that Chevron gas(mid-grade) and a bottle of "Restore" for V-8s' can help at this trying of times with smog.

MonacaYankee

A lean condition causes high NOx. Could be vacuum hose related messing with the readings for the computer.

KD4315

What kind of spark plugs are you running? I've seen the fancy ones lead to a high NOx reading where as Champion Truck Copper plugs seem to be the best. Since you already changed the O2 sensor it could also be a bad cat. I would also run a can of BG44K through your Jeep. Last but not least, what temp TStat do you have? I've known people that have failed CA Smog for High NOx with a 180 TStat that passed as soon as they switched back to a 190.

stew

Spark plugs are autolights.First set ran 33k without any problems.Just replaced with same 1200 miles ago.No indication of lean burn.
T-stat is 195* mopar unit,temp always around 200-210.
I have not replaced O2 sensor in 2 years I have owned her.
Tommorow I will pull plugs(replace W/champions),do compression,and smoke test,inspect vac lines,replace O2 sensor.
Heard good things about BG44K!Been using Rotela 15/40,mopar MO90,restore every 5K.
Only got one free retest.Hope the cat is not pooched..Thanks

DFlintstone

The Champion Coppers (.o35), and an NTK 02 sensor won't hurt anything. Sometimes I bring my cap in and clean it in the sink like a dirty dish, then dry the high temp plastic on the wood stove. When my 02 sensor was toast the idle would cycle every 20 secs or so.

I gather BK-44 is the real deal for cleaning the fuel system, but I wouldn't have anything in there but premium for the test. My CA smog license expired in 81. Slap a carb and some points in there and I'm your guy!

stew

Another FAIL today.HC increased,as well NOx.Here is what I did.
Ran 1/3 can seafoam thur TB.As per directions.
Put pint of "no fail smog test snake oil" in fuel tank.
When smoke mellowed out,wrapped wet rag on tail pipe and checked for exhaust leaks.
Major leak in front of cat.Sealed up and moved on.
Drove the **** out her 140 miles to clear combustion chambers.
Inspected all vac hoses,tested man. vac with gauge.All good.
Replaced O2 sensor,Pulled plugs,compression tested(all weak but with in 10% 133-141 psi.Installed new plugs.
Runs perfect,smooth idle,good power,but wont pass smog **** test.
Start new job tomorrow,12hrs every day till complete.Wont have much time to chase my tail for a while.Tag good till end Feb.
Going to order new APN,CAT.Probley put cat on first and see,APNs are a beaaooch.

MonacaYankee

Cats have a break in period of over 100 miles. Put the new one on a while before retesting it. Performance-curve.com has some good prices plus a 5 percent cherokeeforum discount.

I passed with similar numbers in GA with my 94. It has an exhaust leak in front of the cat too.

stew

Thanks for tip Yankee.Did a quick search,didnt see any magnaflow 339005.
Must be cal carb spec.They have great prices,maybe ill give them a call.

highmileage

I hate to say it but this is why you may have failed your re-test.
Primarily the snake-oil.
I have used the snake oil in the past and it does clean up emissions but after about two full tanks after treatment. The way that stuff works is by generating heat to ash the crud in the system, heat makes HCs'/NO?... You are gonna have to wait a little bit for the re-re-test till that stuff is gone and has done its job.
The new cat can't hurt, just make sure you put about 50mi on it B-4 going back.

stew

Back at chasing high NOx issue.123 hrs in 11 days,Iam a whipped puppy.
Ordered new APD exhaust headed(125.00) thur amazon.Should have it tue.
Going to hold off on cat till manifold is installed.And run retest .
Decided to run water thru throttle body in an attempt to clean carbon from combustion cambers.
What an eye opener!I new of small crack were I repaired crack at collector.
Steam reveiled two more leaks on headed,plus #1 exh.at head was blowing steam...Tightened manifold and stoped that leak.
Hopefully I have found problem.
Will post results after I swap header.Thanks for everyone help.

stew

After replacing exhaust header,NOx readings doubled!Now branded gross polluter.
Had cat replaced today,but don't think this will help.Maybe pull 703s and replace with OEs.Kinda up against a wall,dont know what to do next short of replacing engine.
I disconnect pos. at battery during manifold work.Did this clear memory on eec?
Ill change fuel filter again,and check psi at rail.
Any other suggestions before I retest again are appreciated.Thanks.