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Hydrocarbons too high. How do I adjust?

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  • Hydrocarbons too high. How do I adjust?

    I have an Impco system on my 94 Chevy truck with a 350ci V8. I've tried and failed to pass our required local emissions testing twice with it. It's releasing too high of HydroCarbon levels. It's releasing 465-606 ppm, and the local regulation is a standard of 220 ppm.

    Can anybody tell me what I can adjust or rebuild to get it to burn cleaner HC levels? I have got to get this truck legal ASAP.

    Thank you!

  • #2
    Some of the hings you can check yourself : spark plugs and wires , make sure the timing and advance is within speck.,cng is much pickier on ignition than gasoline .check compression for a low or dead cylinder. Could be a bad 02 sensor , a bad cat converter, but don't start throwing parts at it.. This is an obd 1 system. is the test failing at idle, at 15 mph , at 25 mph , at 1500 rpm ? Really needs a shop to put the engine on a scope. Is this a bi fuel , or dedicated cng fuel system

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    • #3
      Originally posted by Lakewood90712 View Post
      Some of the hings you can check yourself : spark plugs and wires , make sure the timing and advance is within speck.,cng is much pickier on ignition than gasoline .check compression for a low or dead cylinder. Could be a bad 02 sensor , a bad cat converter, but don't start throwing parts at it.. This is an obd 1 system. is the test failing at idle, at 15 mph , at 25 mph , at 1500 rpm ? Really needs a shop to put the engine on a scope. Is this a bi fuel , or dedicated cng fuel system
      Thank you for the feedback. Several other guys wrote to me to say a cat conv as well. I will borrow a compression tester from work this weekend and check that out as well. I already replaced plugs and wires and set the timing.

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