Failed emmisions again

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Oct 22, 2007 | 12:09 PM

13MWZ

Thread Starter

Elder User

Joined: Sep 2002

Posts: 936

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From: Texas

Failed emmisions again

Got back from my second middle east tour and my truck was 6 months past inspection. I took it this morning to get inspected but it failed emmisions again. Last year when this happened the guy doing it realy liked my truck and said he'd give me a break since I was heading over seas again and gave me a pass. I felt guilty about letting him do that but I realy needed a good inspection sticker to get on post.
So anyways, here I am, about 600 miles on a rebuilt engine and carb, new exhaust (including cat), distributor, plugs, and wires. I'm not so sure my carb is in the best of shape anymore and want to ditch the stock 4 brl anyways. But other than that what should I be looking for as far as the emissions junk goes? This is on a 84 F150 4x4 with a 351W HO and C6. I dont know much about the emission system but as far as I can tell everything is hooked up. How do I tell what part isnt working or needs to be replaced? The only part I faild was the hydrocarbons. I'm allowed 220 at both high and low rpm, but I got 931 at high rpm and 840 at low rpm.

Any suggestions are greatly appreciated.

Oct 22, 2007 | 12:21 PM

alxsnmr

Fleet Mechanic

Joined: Mar 2005

Posts: 1,603

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From: St Louis

That sounds like you are either getting too much fuel (check the plugs for complete burn) or the cat isnt working (faulty cat check with a temp gauge infared preferably). Is the air injection pump putting the the air to the cats? Is the EGR stuck open causing too much fuel not to be burned? Is the timing in the wrong spot of the crankshaft? Nice clean airfilter? Carb needing rebuilt?

Last edited by alxsnmr; Oct 22, 2007 at 12:25 PM.

Oct 22, 2007 | 01:48 PM

Franklin2

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Joined: Jan 2001

Posts: 56,977

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From: Virginia

I would rebuild the carb, and try the testing again. Your power valve may be leaking causing it to run rich.

If you get an aftermarket carb, there will be a lot of vacuum lines to disconnect, and the aftermarket carbs are usually jetted a little bit rich, so you run the risk of it not passing again.

And while you are taking the carb off, mark all the vacuum lines, and make sure they are in good shape with no cracks.

Oct 22, 2007 | 07:31 PM

Big_kid

Junior User

Joined: Jun 2007

Posts: 62

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From: Virginia Beach

You say it sat for 6 months. How old is the gas?

Oct 22, 2007 | 08:19 PM

kermmydog

Post Fiend

Joined: Oct 2003

Posts: 9,176

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From: Western Central NV

Is it the stock 4180 Holley 4bbl? If so Franklin2 hit on it I believe. If it is a stock 4180 Holley they did not have power valve protection so a burp can blow the power valve causing a rich mixture. A trick to cutting Hydro Carbon Emissions is to add Acetone to your gas. I run 1oz/10 gal. But with a high hydro Carbon count use more for a few tanks. Many will argue against this but as a former mechanic that held a Class A smog license in California it will help. I have run acetone in my 86 F250 460 for years with no problems at ALL.

Oct 23, 2007 | 08:29 PM

victorcharlie

Tuned

Joined: Oct 2003

Posts: 341

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Clean your EGR valve.

Oct 25, 2007 | 03:45 PM

13MWZ

Thread Starter

Elder User

Joined: Sep 2002

Posts: 936

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From: Texas

Quote:

Originally Posted by Big_kid

You say it sat for 6 months. How old is the gas?

Well it pretty much sat for a year while I was deployed and i went through a couple tanks of gas befoer trying to get it inspected. My dad drove it once or twice a week to keep things rolling. The carb was rebuilt with the engine before I left. Dad said he has another carb in his garage we're gunna swap it out with the stock 4180 and see if that makes any differance. While it's off I'll try some of yalls other tips. Thanks a lot, I appreciate them.