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Really bad emission failure

Discussion in 'GM Powertrain' started by 93pacetruck, Apr 27, 2013.

  1. 93pacetruck

    93pacetruck New Member

    I wanted to know if you would have any thoughts on another emissions problem on a different vehicle. I have a 93 Chev PU with a 350 Automatic that failed emissions at idle for excessive Hydrocarbons. Here are the particulars.Truck has 161,000 miles on it and runs fine but I did a complete tune up on it using all AC Delco parts, plugs, wires, cap, rotor, fuel filter, pcv valve air filter and a new standard brand O2 sensor. Timing is absolutely correct at 0deg. When I was finished I poured 8 oz. of Seafoam treatment through the booster vacuum line to directly clean out the cylinders and added the other 8 oz. to the gas tank. Below I will list the first test results then the 2nd test results which it failed miserably and that is why I come seeking your advice. By the way, the cat is only about a 50 deg. temp difference front to rearFirst failed results at idle Reading AllowedHC ppm 326 220CO% 0.77 1.20CO2 13.8O2% 1.4First failed results @ high speed (2500RPM)HC ppm 126 220CO% 0.59 1.20CO2% 14.3O2% 0.9The only thing that failed was Idle HC at 326. After doing all the work I mentioned here are the new resultsIdle resultsHC ppm 2248 220CO% 6.47 1.20CO2% 13.3O2% 2.0High Speed resultsHC ppm 140 220CO% 0.19 120CO2% 14.2O2% 1.8As you can see the idle numbers especially the HC went completely out of whack. The only other comment I can make about the engine is that when it idles sometimes it will seem to pickup a slight miss.Seems that could be some sensor or even the Computer? Doesn't do it all the time when idling, just occasionally. If you have any thoughts on this matter I would be very happy to hear them.Thank you very muchPat
  2. ahmitchell1

    ahmitchell1 Rockstar 4 Years ROTM Winner 1000 Posts

    Throw some premium in there and drive around for 30 minutes or so at high way speeds and then take it in. See if that works
  3. 93pacetruck

    93pacetruck New Member

    Did that on the way there. Thanks
  4. ahmitchell1

    ahmitchell1 Rockstar 4 Years ROTM Winner 1000 Posts

    So that didn't work? Have you ran some full injector cleaner?
  5. 93pacetruck

    93pacetruck New Member

    Thanks. All the simple things have been tried. This is something way weird going on thats out of the norm

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