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My 02 Kia spectra failed California smog with High HCs at Idle – HC’s measured 157 (Max: 100; Average: 17); CO measured 0.77 (Max: 1.0; Ave: 0.0). Tomorrow, I plan on changing the oil, filters, plugs, plug wires and look for vacuum leaks. Suggestions/alternatives will be appreciated. Besides paying for another smog, is there a way to check the hydrocarbon measurements?
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Just so incorrect information does not enter the database here, three way catalytic convertors have been installed on cars sold in the U.S. and Canada since 1981. The three way catalytic convertor, as you might expect, has three functions….
1. Convert unburnt hydrocarbons (fuel) to carbon dioxide and water vapor
2. Convert carbon monoxide to carbon dioxide
3. Convert nitrogen oxides to nitrogen and oxygenMy guess is the old catalytic convertor still had enough gumption left to burn the hydrocarbons when hot but not at idle. Anyway, congratulations on getting it passed. A friend junked a very nice pickup after failing to solve this same problem.
I have what sounds like the same problem. 93 Jeep GC with 4.0 engine. Has always passed smog no problems and then this time it failed with High HC only at idle. The high speed 2500 rpm works just fine. NOx is good too. I went home and replace all the plugs with NGK, new set of wires, cap and rotor and then changed the oil and filter. Also had run that fuel additive Guarantee not to fail. Failed again the HC was even higher…went from 131 to 161…max is 100, average about 17. I have never replaced the Cat or O2 sensor (only has one before the cat). I replace the O2 Sensor and now am thinking I need to replace the Cat. The tech said he could smell the unburned fuel. I did a run from San Francisco to LA keeping the speed at 65mph and got 19 mpg which is great for this car as it is all wheel drive. Runs with power and just performs great. Does not use any oil and has 161K miles.
I am thinking the Cat needs replacing…any ones thoughts?Thanks
Ya know I find on this 6 cyc that some of the inside manifold bolts are taking about a half turn to tighten….I remember an old 4 banger that had the same problem. Wonder if that might cause a problem but would think they would have to be far looser than half a turn to have a leak. The best way to check for leaks is running at idle and spaying around hoses etc. with carb cleaner and see if it changes the engine speed? There are not many hoses on this engine (jeep 4.0)
Not sure if your jeep has adjustable ignition timing but over advanced timing can also cause high HC.
This model year the Dist. is locked in place. With the great gas mileage I have a hard time with finding fault in the ignition or fuel injectors. I ran the engine cold this morning and sprayed cleaner around all the intake fixtures and manifolds and nothing changed….so I have to assume at this point there are no vacuum leaks. I did change out the O2 sensor and am going to replace the Cat since it is the original one. All new wires, plugs, cap rotor so I am hoping with a new Cat this beast will pass smog. Everything was low except the idle HC test. Max in CA is 100 and it was at 161. They say the average is around 17…hard to believe.
Ok update….Went over to the muffler guy and had the cat replaced and the muffler. Wanted to look at the cat and when we shined a flashlight inside it was totally empty!!! WTF!! Would that have caused the high HC on the smog test? Seems to me that any unburned gas fumes would just pass right on out to the probe they use for the smog test. I did notice that I do not smell any exhaust like I did before but that also could have been a leaking muffler or the above….a totally gone Cat. What is weird is two years ago it passed with flying colors…guess it all blew out the exhaust! We will see…have to throw some more cash at the state to get it tested again. :angry:
OK update: Had the jeep smogged and it was amazing. With a complete tune up and new O2 sensor and the new cat it went from HC=161 to 1.0!!! everything was very low in the readings. That cat and O2 really made the difference as expected. This tells me the engine is fine and with oil consumption about 1 qt per 3000 miles it should be running a long time. Now to look at some suspension noises….it is a 21 yr old car so just like me some of the joints need fixing!! banana:
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