failed the sniffer today - LOW SPEED HC's - HELP!
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From: DFW, Texas
failed the sniffer today - LOW SPEED HC's - HELP! i have a T1 spec cam, FLP's w/ cats, stock heads, SLP LS6 intake, NGK TR 6's @ .038", B&B triflow. what will lower my LOW SPEED HC count? limit is 220 w/ me @ 512. plugs at the correct gap? new O2's? higher idle speed (i was @ 852 by the computer)? what is the max idle speed (1200?)? if i shim the idle up temporaraly, will that let it drop? @ 2530 RPM's my HC's where @ 7! so that could be the way to do it. raise the idle. any thoughts?
also, the cats are new, never used units (20 miles tops), will that effect anything?
also, the cats are new, never used units (20 miles tops), will that effect anything?
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From: Friendswood,TX
Re: failed the sniffer today - LOW SPEED HC's - HELP! How long did you ride around before the test? You need to ride around for a good 30-45 min before testing to get the car up to temp and heat up the cats.
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Staging Lane
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Re: failed the sniffer today - LOW SPEED HC's - HELP! In addition to the above post, you could also try a hotter plug. TR55 plugs with a .060 or .059 gap.
Joel
[ February 20, 2002: Message edited by: C5 Hardtop ]</p>
Joel
[ February 20, 2002: Message edited by: C5 Hardtop ]</p>
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Re: failed the sniffer today - LOW SPEED HC's - HELP! Glenn, your idle speed does effect your HC readings, if you raise it to max speed without setting SES light this may be enough. Also we have been thru this info before but here goes again: HC is from missfires not running rich, if car was running rich enough to cause excess HC, you would have Failed CO at the same time.
Bigger cam causes intake charge to be polluted with exhaust, this dilluted int. charge at stock idle speed doesnt burn well and incomplete combustion causes HC to pump out exhaust. By raising idle speed less time for exh. to contaminate intake and more complete burn happens(less residual exhaust) Leaning idle adjustment will only cause larger miss fires. Slight richening can help slightly. These are facts i have proven with my own emission analyzer and Gen 1 small block(computerized with racy cam). If you understand this it will keep you from wasting time and money using wrong approach to clean up your emissions.
Bigger cam causes intake charge to be polluted with exhaust, this dilluted int. charge at stock idle speed doesnt burn well and incomplete combustion causes HC to pump out exhaust. By raising idle speed less time for exh. to contaminate intake and more complete burn happens(less residual exhaust) Leaning idle adjustment will only cause larger miss fires. Slight richening can help slightly. These are facts i have proven with my own emission analyzer and Gen 1 small block(computerized with racy cam). If you understand this it will keep you from wasting time and money using wrong approach to clean up your emissions.
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From: DFW, Texas
Re: failed the sniffer today - LOW SPEED HC's - HELP! so what is the max idle speed the computer will allow? the emissions tester (equipment) had a range of 350-1200 RPM's. if i use LS1 edit to set idle at 1175 then there should be no SES, right?
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From: new england
Re: failed the sniffer today - LOW SPEED HC's - HELP! Glenn i cant answer about LS1 edit, sounds right to me though.Make sure cats and engine are red hot, Drive for 20+ minutes on hiway, come right in for testing. They may be able to run in diagnostic mode first to see if you fixed problem, before actual retest.
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From: College Station, Tx
Re: failed the sniffer today - LOW SPEED HC's - HELP! Reference:
I wouldn't try and attack a HC with a/f ratio though - as LS1derfull pointed out there are other means.
Make absolutely sure you do not have any mis-fired. The other big contributor to HC output is actually high timing (believe it or not). Do you have a ported MAF? You might try putting a stock MAF back in. Also getting the engine very hot/up to temp helps. AS a last ditch effort try putting a gallon or so of dry-gas (alchohol - normally denatured ethanol or isopropanol) in your car.
Chris
I wouldn't try and attack a HC with a/f ratio though - as LS1derfull pointed out there are other means.
Make absolutely sure you do not have any mis-fired. The other big contributor to HC output is actually high timing (believe it or not). Do you have a ported MAF? You might try putting a stock MAF back in. Also getting the engine very hot/up to temp helps. AS a last ditch effort try putting a gallon or so of dry-gas (alchohol - normally denatured ethanol or isopropanol) in your car.
Chris
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From: DFW, Texas
Re: failed the sniffer today - LOW SPEED HC's - HELP! we are not on rollers as of yet (starts next year for all 95 and down and 96 and up if it has a SES). thanks for the help guys. also, i fully understand what your saying bout the 112 lobe sep. causing the high HC count at idle. i figure if i can get 300 more RPM's @ idle, thats almost half way to where it passed with a count of 7 PPM! raising the engine speed 1600 RPM's (high speed test) dropped the count 505 PPM, i only need to drop the HC PPM by 200 to pass. see where i'm going with this idle thing? raising it will only be temporary, just for testing, then back to 850 it goes (or 750 if it sounds more lopey!)
Re: failed the sniffer today - LOW SPEED HC's - HELP! Glenn98ZM6, you're missing the obvious solution here....you don't need LS1_Edit, just put your foot on the throttle and bring ther RPM up to about 1050RPM. Typically 1100RPM is the max for the idle test. They won't have a clue if you have your foot on the gas or not <img src="gr_grin.gif" border="0"> This is what I did to get my K5 to pass w/o a CAT at idle <img src="gr_grin.gif" border="0"> <img src="gr_grin.gif" border="0"> <img src="gr_grin.gif" border="0">
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From: DFW, Texas
Re: failed the sniffer today - LOW SPEED HC's - HELP! i cant control the speed from in the car when i'm not in it. the tech pushed the peddle, and watches the screen on the test equipment.
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From: Texas
Re: failed the sniffer today - LOW SPEED HC's - HELP! Steve Cole did some timing and fuel/air changes to my B1 cam'd WS6 when tuning it. It has been several years since he did this, but he commented on lope of the cam being heavily affected by timing changes and a small change in fuel delivery. I mention this, as my PCM was recording misfires on random cylinders when he had the TECH II hooked to it at idle and when I would decel to a stop using the gears. As mentioned above, misfires dump a bunch of unburned HCs into the exhaust. Once he did the fuel and timing changes, the lope(at the same idle speed) was dramatically reduced. The misfire records basically went to zero, as well. He still ended up raising my idle 75rpm to produce a basically stock smooth idle.
Todd
[ February 21, 2002: Message edited by: BLK 98WS6 ]</p>
Todd
[ February 21, 2002: Message edited by: BLK 98WS6 ]</p>
Re: failed the sniffer today - LOW SPEED HC's - HELP! Sorry Glenn98ZM6, I didn't realize you weren't in the car. Here in WA State we drive the car on the rollers for the Tech.
Todd, do you know exactly what Steve tweaked?
Todd, do you know exactly what Steve tweaked?