19Comanche 87 Posted February 7, 2023 Share Posted February 7, 2023 I've been trying for months now to get my 1987 Comanche to pass emissions in DE. it keeps failing with high Carbons. I've replaced the o2 sensor, ran smoke tests for leaks, and tried running "Guaranteed to Pass" in my fuel. when i bought the truck it was tagged in Maryland which didn't have emissions tests. and the charcoal canister wasn't hooked up (red Flag). could the charcoal canister be bad? any ideas as to what is make it fail? its the 4.0l inline 6. its also failing the gas tank pressurizing test. could these issue be related? any suggestions would be greatly appreciated. Link to comment Share on other sites More sharing options...
pizzaman09 Posted February 7, 2023 Share Posted February 7, 2023 Where I live in PA, we only have a visual for emissions, so I'm not too familiar with states that actually sniff the exhaust. However, high carbon to me sounds like you are either burning oil or running lean. If you ran a smoke test, I suspect the intake is leak free and all your header bolts are tight. I'd look at the egr setup and test to confirm it is operating correctly. I'd also check to make sure your crank case ventilation is functioning, not clogged or just pumping oil into the intake. Link to comment Share on other sites More sharing options...
AZJeff Posted February 7, 2023 Share Posted February 7, 2023 Let's start with some basics. I think your emissions failure is due to "excessive hydrocarbons", as that is the term used when evaluating exhaust emissions. Excessive hydrocarbons (aka "high HC") is in indication your Jeep is not burning the fuel correctly, meaning that there is too much fuel for a given amount of air entering the engine, or what fuel it IS getting is not burning fully due to poor compression, or poor ignition, or both. I assume you have some sort of formal report from a Delaware state approved emissions testing facility that would indicate what the results of their testing indicated. If you can attach a copy, or transcribe what is in the report, it would help us figure out what is going on. Just guessing and trying this or that is likely to be an exercise in frustration, so we need more details. Link to comment Share on other sites More sharing options...
fiatslug87 Posted February 8, 2023 Share Posted February 8, 2023 Get yourself a Renix Engine Monitor, my guess is the O2 sensor isn’t working properly. New O2 sensors have not been working correctly, search the forum for more info on that. Link to comment Share on other sites More sharing options...
cruiser54 Posted February 8, 2023 Share Posted February 8, 2023 THIS^^ Link to comment Share on other sites More sharing options...
19Comanche 87 Posted February 8, 2023 Author Share Posted February 8, 2023 16 hours ago, AZJeff said: Let's start with some basics. I think your emissions failure is due to "excessive hydrocarbons", as that is the term used when evaluating exhaust emissions. Excessive hydrocarbons (aka "high HC") is in indication your Jeep is not burning the fuel correctly, meaning that there is too much fuel for a given amount of air entering the engine, or what fuel it IS getting is not burning fully due to poor compression, or poor ignition, or both. I assume you have some sort of formal report from a Delaware state approved emissions testing facility that would indicate what the results of their testing indicated. If you can attach a copy, or transcribe what is in the report, it would help us figure out what is going on. Just guessing and trying this or that is likely to be an exercise in frustration, so we need more details. i don't have a copy at the moment. i will be running it through again tomorrow to see if it will pass. i did find a small exhaust leak just before the cat. not sure if this would be significant enough to fail emissions. ive never really worked on a car that didnt pass emissions so all this is kinda new to me. ive replaced the spark plugs and had some seals replaced. it was having a hard time starting when i first got the truck but seems to start better. could this be a low compression problem? Link to comment Share on other sites More sharing options...
19Comanche 87 Posted February 8, 2023 Author Share Posted February 8, 2023 14 hours ago, fiatslug87 said: Get yourself a Renix Engine Monitor, my guess is the O2 sensor isn’t working properly. New O2 sensors have not been working correctly, search the forum for more info on that. i replaced the o2 sensor with an aftermarket one and it didnt look the same as the original. i wasnt able to find an oem sensor so i just went with the aftermarket. could this be the cause? do all o2 sensors look the same or can they look different and still work? still new to all of this. Link to comment Share on other sites More sharing options...
fiatslug87 Posted February 8, 2023 Share Posted February 8, 2023 This was my experience if you haven’t found it already. Link to comment Share on other sites More sharing options...
19Comanche 87 Posted February 8, 2023 Author Share Posted February 8, 2023 7 minutes ago, fiatslug87 said: This was my experience if you haven’t found it already. the one i used i think was a bosch. might have to try and find a junk yard one to replace it with. Link to comment Share on other sites More sharing options...
fiatslug87 Posted February 8, 2023 Share Posted February 8, 2023 I tried NTK, Bosch and OmixAda none worked properly. Let us know how the retest goes after the exhaust leak was fixed. Good luck. Link to comment Share on other sites More sharing options...
AZJeff Posted February 8, 2023 Share Posted February 8, 2023 An emissions test report would be helpful to make sure the OP is actually attacking the correct issue with new parts. Link to comment Share on other sites More sharing options...
eaglescout526 Posted February 8, 2023 Share Posted February 8, 2023 Just my two cents. I have NOS O2 for the 2.5L, they say autolite on them. Link to comment Share on other sites More sharing options...
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