Truck failed emissions

[motorcritter]

When I worked for Honda, when we had a car that would fail Maryland emissions, a valbe adjustment and an oil change always did the trick (unless the motor was so clapped out, it would never pass). Seems like a lot of unburned fuel can end up in the crankcase and play hell on the numbers.

Probably don't need a valve adjustment, but an oil change- if it's been 'a while'- might help.
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[Lattimer]

Originally Posted by motorcritter

When I worked for Honda, when we had a car that would fail Maryland emissions, a valbe adjustment and an oil change always did the trick (unless the motor was so clapped out, it would never pass). Seems like a lot of unburned fuel can end up in the crankcase and play hell on the numbers.

Probably don't need a valve adjustment, but an oil change- if it's been 'a while'- might help.
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Its got about 50 miles on the oil.

[ekgguy]

You might try looking at the jets in the carb. Might have to rejet. My dad had to do that to get his old Galaxy to pass, but he had a Holley carb. Just my .02

[JointTech]

wow i thought California was bad but I dont have to smog mine at all. 1975 and under I think.

[biohazardbill]

Hmmm weird. In Michigan (when i lived there and they had emissions testing) they didnt require it on cars past a certain year since they werent factory built to the current emissions specs. I dont see how they can force you to pass a test that the car wasnt originally meant to pass in the first place. It's like seatbelts. Until it was mandatory and not an option they cannot give you seatbelt tickets for cars that werent originally equipped with them.

[Eddie H.]

First off, it sounds like your idle mixture is too rich.

If you're idling at 1000 RPM, you could be pulling fuel from the transition circuit\ primary jets also. Back the idle down to 650-700rpm.

To adjust the idle mixture for best emissions, turn each screw in until the idle starts to get rough, back out until it smooths out, then turn each mixture screw back in very slowly until the rpm just starts to drop. For the emission test, you might want to go another 1/8 to 1/4 inch farther in past that point.

If you have a vacuum spark advance distributor, unhooking the vacuum line and plugging it during the test may also help.

[Lattimer]

Originally Posted by Eddie H.

First off, it sounds like your idle mixture is too rich.

If you're idling at 1000 RPM, you could be pulling fuel from the transition circuit\ primary jets also. Back the idle down to 650-700rpm.

To adjust the idle mixture for best emissions, turn each screw in until the idle starts to get rough, back out until it smooths out, then turn each mixture screw back in very slowly until the rpm just starts to drop. For the emission test, you might want to go another 1/8 to 1/4 inch farther in past that point.

If you have a vacuum spark advance distributor, unhooking the vacuum line and plugging it during the test may also help.

Idle was 700 on the first test. I had read that increasing it might help, so I turned it up to 1000 for the second test.

Thanks for the tips, I'll try that.

[sleepertruck72]

High HC's are mostly problems with ignition components. Since you already have gone through these, I agree with the rich running carb. being the culprit. Also, if you have not already or recently, I would replace the PCV valve...

[sixtysevengmc]

Edelbrock carbs are extremely sensitive to dirt and other contaminates in the fuel.

[Lattimer]

Originally Posted by sleepertruck72

High HC's are mostly problems with ignition components. Since you already have gone through these, I agree with the rich running carb. being the culprit. Also, if you have not already or recently, I would replace the PCV valve...

That's new also.

[Lattimer]

Originally Posted by sixtysevengmc

Edelbrock carbs are extremely sensitive to dirt and other contaminates in the fuel.

I have heard that. I put an inline filter in right before the carb, but it may have gotten crap in it before I did that.

Everything seems to work fine other than the emissions though.