CA smog fail 5 times.... running out of ideas
Hey everyone!
Recently picked up a 93 Jeep Cherokee Country with a 4.0. I failed CA smog on Nox at 15mph and everything else passed with flying colors going in with no knowledge on the vehicles past and the smog tech told me I needed a new o2 sensor. Changed it and came back to fail again on Nox. Since then, I have smogged a total of 4 more times and changed the following parts: o2 sensor, carb legal cat, Coolant Temp Sensor, MAP sensor, map sensor vacuum line, Fuel Filter, Oil, Muffler for back pressure, 165 degree thermostat(will be changing back to 195 thought it could help cool), champion spark plugs, rotor + distributor cap. I also wired the e-fan to a switch and ran it during the test. To my understanding, the 93 xj does not have an egr. One of my last ideas would be the charcoal canister. Do you think it could affect Nox? I have not looked too much into it, but its one of the last emissions control devices that i haven't touched. Here is the Results of the last smog test. https://cimg9.ibsrv.net/gimg/www.che...749e21682.jpeg here is some pictures of my engine bay to see if anyone can see anything off about it. https://cimg4.ibsrv.net/gimg/www.che...06c97fdd4.jpeg https://cimg1.ibsrv.net/gimg/www.che...fc83da05f.jpeg https://cimg2.ibsrv.net/gimg/www.che...cee5efa5e.jpeg https://cimg4.ibsrv.net/gimg/www.che...317b37e98.jpeg I appreciate all the help in advance ! Thank you! |
First item of concern is mixture. Which can be observed via the voltage signal generated by the O2 sensor(s). Though a typical multimeter probably won't be sufficient (because it takes periodic samples and averages them). Do you know anyone with a digital oscilloscope? Like a HAM radio hobbyist?
Are those after-market injectors? Has the vehicle ever passed emissions since those were installed? Have you performed any carbon build-up cleaning? Has your fuel pressure been tested to ensure that it is within spec both at idle and under load? (I ask because the RPM was similar in both tests, but the 15mph would have been under far less load). |
Could be a vacuum leak somewhere, but that will have you running rich. Not sure that would bother the NOx reading. What do you know about the condition of your injectors? One of our old timers swears by BK44 as the only injector cleaner that actually works. Wouldn't hurt to give it a shot.
Off topic: That's a pretty clean 93 you have there! :thumbup1: By the way, you can lose the heater control valve. Just run 5/8" heater hose and 3/4" *heater hose and cap the vacuum lines, and say goodbye to that troublesome waste of space. *I don't recall which one is top and which is bottom, but it's easy to tell when you are looking at them. |
Originally Posted by BlueRidgeMark
(Post 3553460)
Could be a vacuum leak somewhere, but that will have you running rich. Not sure that would bother the NOx reading. What do you know about the condition of your injectors? One of our old timers swears by BK44 as the only injector cleaner that actually works. Wouldn't hurt to give it a shot.
Off topic: That's a pretty clean 93 you have there! :thumbup1: By the way, you can lose the heater control valve. Just run 5/8" heater hose and 3/4" *heater hose and cap the vacuum lines, and say goodbye to that troublesome waste of space. *I don't recall which one is top and which is bottom, but it's easy to tell when you are looking at them. |
NOX is a sign of high combustion temps. I would suggest using some sea foam in a quarter tank of gas and driving it until almost empty. You might have carbon build up making hot spots inside the combustion chamber
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Take this post (mine) with a pound of salt - as I have no idea what I am talking about.
But - at some point - maybe 15 years ago - some wizard (in Florida) thought our engine needed these rather thick (thicker than simple foil) aluminum covering the top of the engine, almost wrapping each of the plugs. It has stayed there since. It must have had something to do with temperature disbursement, We have never failed an inspection since. |
My 95 passes CT emission standards without a cat but I get the tank down to a very low level and pour in about 3 bottles of isopropyl alcohol. I dont know how your limits vary from here. After the test I fill the tank and drive it for the next few days till empty. Might be worth a try.
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Originally Posted by 4.3L XJ
(Post 3553468)
NOX is a sign of high combustion temps. I would suggest using some sea foam in a quarter tank of gas and driving it until almost empty. You might have carbon build up making hot spots inside the combustion chamber
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i forgot to mention i have tried to sea foam it twice. The car did not smoke the first time and the second time it smoked for all of 2 seconds.
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Originally Posted by Cummins93
(Post 3553483)
My 95 passes CT emission standards without a cat but I get the tank down to a very low level and pour in about 3 bottles of isopropyl alcohol. I dont know how your limits vary from here. After the test I fill the tank and drive it for the next few days till empty. Might be worth a try.
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Originally Posted by jordan96xj
(Post 3553457)
First item of concern is mixture. Which can be observed via the voltage signal generated by the O2 sensor(s). Though a typical multimeter probably won't be sufficient (because it takes periodic samples and averages them). Do you know anyone with a digital oscilloscope? Like a HAM radio hobbyist?
Are those after-market injectors? Has the vehicle ever passed emissions since those were installed? Have you performed any carbon build-up cleaning? Has your fuel pressure been tested to ensure that it is within spec both at idle and under load? (I ask because the RPM was similar in both tests, but the 15mph would have been under far less load). Thank you so much!! |
Originally Posted by Lancyy
(Post 3553499)
i forgot to mention i have tried to sea foam it twice. The car did not smoke the first time and the second time it smoked for all of 2 seconds.
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Originally Posted by 4.3L XJ
(Post 3553509)
Did you pour it down the intake after you replaced the cat? That process can knock out a cat. Just putting it in the gas tank is preferable
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Is you jeep stock with stock size tires ? because if you have larger tires it will lower your rpm and at 15mph that can lug the engine with the 50% load ,
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Originally Posted by tech
(Post 3553532)
Is you jeep stock with stock size tires ? because if you have larger tires it will lower your rpm and at 15mph that can lug the engine with the 50% load ,
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