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Forum > Failed Smog Test > Question

1997 Jeep Wrangler Sport 4.0 failed smog for high HC

the first smog test passed everything except the (HC PPM) measurments. At 15mph it measured 73. According to the paperwork the max it should read is 53. At 25mph it measured 45 and max it should read is 37. So I took home and gave it a tune up, plugs, wires, cap, rotor. and replaced both O2 sensors. I took back and failed the retest. This time I only failed the 15 mph measurement of (HC PPM. The 25mph measurement barely passed and it read 37 and max it can read is 37. The 15 mph measurement read 61 which is down from 73 but still over the max 53. What do you think could be causing this problem? Do you think the cat can be bad and causing this problem? Any advice would be greatly appreciated. Thanks
Answer:

Could be the CAT, but we'd recommend making sure your Jeep is in proper fuel control first. Sounds like you've done the proper repairs. If the emission computer is increasing fuel when it receives a lean signal from the oxygen sensor; and you've replaced the oxygen sensors, then you can perhaps consider a bad Catalytic Converter. posted by SmogTips Support

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