GM Truck Club
Founded in 2004 ~ We're the #1 Chevy Truck & SUV Forum.
Silverado & Sierra | Tahoe & Yukon | Suburban & Yukon XL | SUV & CROSSOVER
Results 1 to 5 of 5
  1. #1

    Default Really bad emission failure

    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. #2


    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
    2009 chevy 1500 z71 4x4
    2.5 ccm level,2.5 inch rear blocks 305/60/18 coopers stt,Debadged,10 series flow w/dual exit in front or right rear tire, KN CAI, diablo InTune, 18% tint all the way around ,spec-d euro headlights with black housings,winjet smoke LED tail lights,putco LED third brake light smoked, fab fours front bumper with 10k warn winch, RK sports ram air hood
    1965 c10 swb, zz4 350 with the hot cam and fast burn heads and a 780 Holley on top, richmond super street 5 speed,restorod

  3. #3


    Did that on the way there. Thanks

  4. #4


    Quote Originally Posted by 93pacetruck View Post
    Did that on the way there. Thanks
    So that didn't work? Have you ran some full injector cleaner?

  5. #5


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

Similar Threads

  1. P0442 Evaporative Emission Leak Detected
    By Big_Ben in forum General Chevy & GM Tech Questions
    Replies: 4
    Last: 10-07-2010, 07:26 AM
  2. Carb/Emission Problems
    By hiandfast in forum Chevy C/K Truck Forum
    Replies: 1
    Last: 04-03-2010, 02:56 AM
  3. Honda rolls out a new zero-emission car
    By ChevyFan in forum The Coffee Shop ~ Chit Chat
    Replies: 0
    Last: 06-16-2008, 11:40 AM
  4. HELP! Emission Sticker Info Needed
    By zippy in forum Chevy Suburban Forum (GMC Yukon XL)
    Replies: 4
    Last: 02-09-2008, 03:07 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts