Emissions fail - any advice

[jlolson]

I've failed emissions twice on my '71 C20 5.7L.

Prior to first test:
Vehicle was not running when I bought it. Fresh oil/filter, new plug wires, new gas tank, flushed fuel lines, new carburetor, timing adjusted, idle screw adjusted but left idle fuel mixture screws alone (new Edelbrock carb, thought it would be dialed in).

Pollutant: Reading/Standard - Result
Loaded Hydrocarbons (HC) in PPM: 132/450 - PASS
Loaded Carbon Monoxide (CO) in %: 3.54/3.75 - PASS
Idle Hydrocarbons (HC) in PPM: 379/450 - PASS
Idle Carbon Monoxide (CO) in %: 8.94/5.0 - FAIL

Prior to second test:
Idle fuel mixture screws dialed down as low as possible without stalling, Idle set precisely 550RPM in drive, replaced PCV valve, new spark plugs, burned one can of "guaranteed to pass" emissions formula, filled up with 91 octane, added 1 can of octane booster, drove for about 20 minutes on the freeway to get it hot as hell prior to testing.

Pollutant: Reading/Standard - Result
Loaded Hydrocarbons (HC) in PPM: 149/450 - PASS
Loaded Carbon Monoxide (CO) in %: 5.68/3.75 - FAIL
Idle Hydrocarbons (HC) in PPM: 119/450 - PASS
Idle Carbon Monoxide (CO) in %: 1.88/5.0 - PASS

I'm going to give this one last try prior to taking it to a shop. I may have screwed up the "guaranteed to pass" emissions formula by not running the tank completely empty (looked empty but when I filled up it only took 15G). I'm going to run it empty again and put more fresh high octane. I also plan on changing the oil again, the engine was likely all sludgey after sitting for 4 years and 2 oil changes won't hurt.

I'd really appreciate any suggestions because I'm out of ideas. I've already spent a small fortune on this thing and can't get it licensed. I really don't need to start dealing with a mechanic on this truck, I bought it so I could do the work myself. Any tips/tricks/repairs before I go again???????

[69GMCLonghorn]

You went the wrong way. Excessive carbon monoxide indicates a LEAN mixture, not fat. So you were running lean at idle on the first test and OK in the midrange. On the 2nd test, you got the idle mixture right, but something affected the midrange and caused you to run lean under a load.

Excessive Hydrocarbons indicate a fat mixture. Edelbrocks typically run leaner than Holley's from my experience. Richen it up, and possibly jet it up one size if possible and you may pass. Also, try running some marvel mystery oil through the gas and oil per the bottle's recommendations. Not sure if that will work, but if it's been sitting for a while, I think it's supposed to clean things out.

[jlolson]

Originally Posted by 69GMCLonghorn

You went the wrong way. Excessive carbon monoxide indicates a LEAN mixture, not fat.

Excessive Hydrocarbons indicate a fat mixture. Edelbrocks typically run leaner than Holley's from my experience. Richen it up, and possibly jet it up one size if possible and you may pass. Also, try running some marvel mystery oil through the gas and oil per the bottle's recommendations. Not sure if that will work, but if it's been sitting for a while, I think it's supposed to clean things out.

I leaned it up with the IFM due to the Test#1 fail for idle CO. For test #2 idle CO was much better but the loaded CO jumped up and failed. Is this a case of finding a happy medium? Test #2 results indicate I can move the IFM screws back out a little. BUT, I thought the IFM and Idle screw only impact the way the carb runs at idle and really had nothing to do with air/fuel mixture when you step on the gas. Am I wrong?

[truckster]

I've had success in the past running my old carbureted Subaru with denatured alcohol in the tank. I ran it down to about 5 gallons of gas and added a gallon of denatured. I had to boost up the idle speed a little bit to get it to idle smoothly. The tech at the I/M station said, "I don't know what you did, but you sure cleaned this thing up."

[69GMCLonghorn]

Originally Posted by jlolson

I leaned it up with the IFM due to the Test#1 fail for idle CO. For test #2 idle CO was much better but the loaded CO jumped up and failed. Is this a case of finding a happy medium? Test #2 results indicate I can move the IFM screws back out a little. BUT, I thought the IFM and Idle screw only impact the way the carb runs at idle and really had nothing to do with air/fuel mixture when you step on the gas. Am I wrong?

My feeling is you have something funky (beyond adjustment) going on with that carb. What is wrong, I don't know, but everything shouldn't have changed according to what you just said. If you go to certain smog shops, sometimes they can run the truck on the dyno without actually running a test to make sure it will pass or not. If it's a fix-it shop, they can adjust the carb until it passes (or until they find the problem).

[vectorit]

Wow, AZ requires you to smog your 1971 truck. I had to look it up, and sure enough you guys have to smog everything from 1967 on up.

Here in CA where I thought just about every law was out of whack, CA exempts everything pre 1975 huh.

If I were you, and others will prolly scoff at this. But I'd find a good 1971 Q-jet and temporarily swap out the Edlebrock, since IIRC those carbs aren't smog legal anyway. So you may be wasting your time? I'd dunno, just throwin it out there.

[leddzepp]

Try running 87 octane fuel instead. When I had to take emissions tests in the past this helped. I have had several smog techs tell me this too.

[leddzepp]

Originally Posted by vectorit

Here in CA where I thought just about every law was out of whack, CA exempts everything pre 1975 huh.

Pre-76

[mclairmo]

When CA still required smog checks on my 67 Camaro, I took it to many smog testers till I found a Korean guy that just passed it, no questions asked even though I had no smog equipment and all aftermarket stuff. I also knew a guy that merely needed the VIN and $200 and could get it passed. My buddy found another smog guy that played his carb until it passed and then put it back to where it would actually run right.

[leddzepp]

Originally Posted by mclairmo

When CA still required smog checks on my 67 Camaro, I took it to many smog testers till I found a Korean guy that just passed it, no questions asked even though I had no smog equipment and all aftermarket stuff. I also knew a guy that merely needed the VIN and $200 and could get it passed. My buddy found another smog guy that played his carb until it passed and then put it back to where it would actually run right.

That was before a 50K fine was imposed on illegal smog checks. You won't find anyone doing this anymore, unless they don't care about their livlihood. I used to give my neighbor $50 and the VIN to my old truck. It passed smog and never even left my driveway

[vectorit]

I just read one of your other posts, and in it you say you are running headers?

If this is true, here in CA they would fail you on just the visual.

If your state allows this, then you need to take into account for those headers while figuring out your A/F settings.

In that other post, you also mentioned you are using an HEI with 7mm plug wires that are melting on the headers. Bad ignition will affect your smog test also, since you are probably arching on the header pipes from the melted wires.

I'm no expert at emmsions testing, but these I think would be pretty important issues to address.

[john]

Back when mine was still under smog rules I had them check the emissions before the test, Then if an adjustnent was needed it was done before the actual test.

[big_al_71]

Originally Posted by mclairmo

When CA still required smog checks on my 67 Camaro, I took it to many smog testers till I found a Korean guy that just passed it, no questions asked even though I had no smog equipment and all aftermarket stuff. I also knew a guy that merely needed the VIN and $200 and could get it passed. My buddy found another smog guy that played his carb until it passed and then put it back to where it would actually run right.

Here in Florida they tried that smog testing and of course it did not last but maybe a couple of years because the samething happened just slip the guy a $50.00 and you passed. They finally realized that there were too many crooked employess and shut it down completely....

[coloradosean2009]

Lean mixture will lower CO. not the other way around.

The mixture screws on an edlebrock only change the idle mixture. The difference between the two under load measurments would indicate a testing error (assuming that nothing else changed).

Grounded spark causing a miss will lift the hydrocarbon count. I don't think that is it.

Bring your idle mix up a little. Get your idle around 850.

Test again. In Colorado, the retests are free. Once I told the guy to retest three times in a row. It passed on the third without any adjustments. I think that the test probe is not the most accurate.

[mclairmo]

Originally Posted by leddzepp

That was before a 50K fine was imposed on illegal smog checks. You won't find anyone doing this anymore, unless they don't care about their livlihood. I used to give my neighbor $50 and the VIN to my old truck. It passed smog and never even left my driveway

The good ol days.

[texanidiot25]

Move to Texas. As long as your lights all flash and your horn goes beep, it passes.

[jlolson]

Originally Posted by texanidiot25

Move to Texas. As long as your lights all flash and your horn goes beep, it passes.

My horn doesn't beep either

[Sport/Truck]

Originally Posted by leddzepp

Try running 87 octane fuel instead. When I had to take emissions tests in the past this helped. I have had several smog techs tell me this too.

+1 on low octane. The lower the octane you'll have complete fuel burn and will eliminate any problems.
s/t

[msgross]

Originally Posted by jlolson

My horn doesn't beep either

you need to move to Indiana... no inspections at all!

[crm318]

Yeah, in Texas, it 14.00 dollars (blinkers, horn, tail lights, and wipers all work) and youre on your way. Its a restorers dream.

[texanidiot25]

And you have to have muffled tail pipes 'past the doors' is the basic rule of thumb, but if you find a cool shop they can even let that slide I'd wager.

[QKENUF4U]

NO OCTANE boost or high octane gas.....that screwed ya right there.... OCTANE SLOWS THE BURN !!!... anyways get a can of acetone, dump in gas tank, set mixture screws correctly (turn in till stumbles/idles rough then turn out 1/2-1 turn) set idle at 1000-1500rpm.... make sure its at operating temp when ya get there and dont idle in line.... (ex phoenix resident just went thru getting my 91 to pass)

[truckdude239]

IN GREAT OLD NC any vehicle 35 years or older does not have to pass any kind fo inspection

[vegaschevy]

Originally Posted by leddzepp

That was before a 50K fine was imposed on illegal smog checks. You won't find anyone doing this anymore, unless they don't care about their livlihood. I used to give my neighbor $50 and the VIN to my old truck. It passed smog and never even left my driveway

There are huge fines here and you can still find $100 smog checks EVERYWHERE!!!! 100 bucks is a TOIN of money to someone making 7 bucks an hour.

I have been going to the same place and many people for years!

[dwcsr]

Originally Posted by texanidiot25

And you have to have muffled tail pipes 'past the doors' is the basic rule of thumb, but if you find a cool shop they can even let that slide I'd wager.

They inspected my 59 from accross the parking lot, never even went in the bay.