It won't pass emissions! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

elwood · 12-09-2003, 05:21 PM

Here's the deal, when I take the truck through state inspection, It does great, except for the idle test. Carbon monoxide and hydrocarbons at idle are way over the limit. It seems like theres a little unburnt fuel passing through the system. I have an eldelbrock carb, slightly cammed 350.

What do I need to do to get this thing to pass?

Tom · 12-09-2003, 05:28 PM

LOL, yeah I get that every time here in phoenix. Turns out somehow the answer is to DROP the base timing down and run ported vaccum for the advance

Destructo · 12-09-2003, 05:29 PM

It may be missing a little bit, mine is missing some but I don't think its related to my carb or ignition system. I think my cam is bad, its got some knocking in the engine too, so I think thats my problem. Maybe your idle mixture is wrong or you have some bad ignition parts.

Eyegore · 12-09-2003, 05:43 PM

I feel your pain, I went through the same problem last April, after 4 trips and $350 later even trying to get a waiver it finally passed after the carb as rejetted by a mechanic.

stepside454 · 12-09-2003, 05:45 PM

also adjust the idle mixture screws in. youll have to idle it back up after wards. turn idle mixture screews in all the way till you feel it start to resist, than back out about 3/4 turn & try that.

Dirty Dan · 12-10-2003, 01:46 AM

I said "forget it" and took it to a place that works on drag cars, they got it to pass. It went from 2600 hc to 13 hc.

Scrubby · 12-10-2003, 02:16 PM

Whenever I don't pass on the idle, I lean out the idle mixture screws and get a new air filter. That usually does the trick for me.

**old Rusty C10** · 12-10-2003, 02:49 PM

id also throw a new set of plugs that always helped me

elwood · 12-10-2003, 04:35 PM

Leaned it out a little, messed with the timing...boom! Passed!

Barely...

Thanks for the comments!

slow69 · 12-10-2003, 11:52 PM

i just got my 82 to pass... it was way rich the first time and the shops around here wanted $50+ just to tell me what was wrong so instead i bought a $25 vacuum gauge, adjusted the idle screws and timing until i got max vacuum with minimum turns out and it passed easily.
i hate messing with emissions in arizona but at least it's not california!

12-09-2003, 05:21 PM	#1
elwood Keep it gangsta! Join Date: Dec 2003 Location: Peoria, Arizona (Phoenix Area) Posts: 102	It won't pass emissions! Here's the deal, when I take the truck through state inspection, It does great, except for the idle test. Carbon monoxide and hydrocarbons at idle are way over the limit. It seems like theres a little unburnt fuel passing through the system. I have an eldelbrock carb, slightly cammed 350. What do I need to do to get this thing to pass? __________________ 1984 K5 Blazer 305-NP208-700R4 Ex Police Unit It's old school, but moves along nicely... '78 C-20 - SOLD

12-09-2003, 05:28 PM	#2
Tom driving is in my blood Join Date: Dec 1999 Location: Mesa AZ Posts: 5,748	LOL, yeah I get that every time here in phoenix. Turns out somehow the answer is to DROP the base timing down and run ported vaccum for the advance __________________ -78 c10 short/step: 388cid, M20, 5/5 drop, lots more. Playtoy and first vehicle. -98 c1500 x-cab: 5.7L, 17" rims, 5/6 drop, flowmaster, helper bags,NBS rear disk brakes. -02 Suburban 4x4: leveled front -CBR600F4i, CBR600RR, CBR1000RR, and standup skis DISCLAIMER: I cant spell for the life of me.

12-09-2003, 05:43 PM	#4
Eyegore What Hump? Join Date: Apr 2003 Location: New River AZ Posts: 2,009	I feel your pain, I went through the same problem last April, after 4 trips and $350 later even trying to get a waiver it finally passed after the carb as rejetted by a mechanic. __________________ Lil red 86 c-10 99 Sub 78 Camper Special w/ 454

12-09-2003, 05:45 PM	#5
stepside454 Registered User Join Date: Nov 2003 Location: st. louis area Posts: 1,551	also adjust the idle mixture screws in. youll have to idle it back up after wards. turn idle mixture screews in all the way till you feel it start to resist, than back out about 3/4 turn & try that. __________________ 75 GMC C-15 short/step factory 454, lowered

12-10-2003, 01:46 AM	#6
Dirty Dan Oh Look Out! Join Date: Aug 2003 Location: M'boro TN, Posts: 505	I said "forget it" and took it to a place that works on drag cars, they got it to pass. It went from 2600 hc to 13 hc. __________________ Dan's Webshots "I have a lot of growing up to do... I realized that the other day inside my fort" - Zack Galifianakis.

12-09-2003, 05:29 PM	#3
Destructo Registered User Join Date: Sep 2003 Location: Lewisville, NC Posts: 1,836	It may be missing a little bit, mine is missing some but I don't think its related to my carb or ignition system. I think my cam is bad, its got some knocking in the engine too, so I think thats my problem. Maybe your idle mixture is wrong or you have some bad ignition parts.

12-10-2003, 02:16 PM	#7
Scrubby Check out GMTrucks.org Join Date: Sep 2003 Location: Boise, Id Posts: 284	Whenever I don't pass on the idle, I lean out the idle mixture screws and get a new air filter. That usually does the trick for me.

12-10-2003, 02:49 PM	#8
old Rusty C10 Robert Olson Transport Join Date: Oct 2002 Location: recent transplant to NC USA Posts: 20,310	id also throw a new set of plugs that always helped me __________________ Bob 1951 International running on a squarebody chassis "If a man's worth is judged by the people he associates himself with, then i am the richest man in the world knowing some of the fine people of this board" http://67-72chevytrucks.com/vboard/a...t.php?f=25&a=9 (you can review the site rules here!) PM Me for your vehicle/parts hauling needs in the North East US or see my Facebook page Robert Olson Transport Live each day to the fullest.. you never know when fate is going to pull the rug out from under you... I hate cancer!!

12-10-2003, 04:35 PM	#9
elwood Keep it gangsta! Join Date: Dec 2003 Location: Peoria, Arizona (Phoenix Area) Posts: 102	Leaned it out a little, messed with the timing...boom! Passed! Barely... Thanks for the comments! __________________ 1984 K5 Blazer 305-NP208-700R4 Ex Police Unit It's old school, but moves along nicely... '78 C-20 - SOLD

12-10-2003, 11:52 PM	#10
slow69 Registered User Join Date: Dec 2000 Location: Flagstaff, AZ Posts: 140	i just got my 82 to pass... it was way rich the first time and the shops around here wanted $50+ just to tell me what was wrong so instead i bought a $25 vacuum gauge, adjusted the idle screws and timing until i got max vacuum with minimum turns out and it passed easily. i hate messing with emissions in arizona but at least it's not california!



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