94 Tbird lx 4.6 Evap smog fail - TCCoA Forums
 
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post #1 of 9 (permalink) Old 04-05-2016, 02:04 PM Thread Starter
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94 Tbird lx 4.6 Evap smog fail

I recently went to get my car smogged and it failed the evap test where they hook the machine onto the gas cap and pump it. Does anyone have a diagram of the evap system? all the hoses and such or any suggestions to why it failed thank you have a nice day -Zak
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post #2 of 9 (permalink) Old 04-05-2016, 02:20 PM
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Bad cap maybe?

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post #3 of 9 (permalink) Old 04-05-2016, 02:22 PM Thread Starter
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Could be but it locks up tight.
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post #4 of 9 (permalink) Old 04-05-2016, 02:35 PM
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No diagram handy but there's several rubber hose junctions that go from the tank to the line parallel to the fuel lines, up to the charcoal canister, and purge valve up front and there to the to the intake that will dry rot and fail over the cars lifetime, get yourself a roll of emissions hose, follow the path and replace them all.

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post #5 of 9 (permalink) Old 04-05-2016, 02:43 PM Thread Starter
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Thank you Matt I will do that today
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post #6 of 9 (permalink) Old 04-05-2016, 03:14 PM
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Is the check engine light on?

BTW, the purge flow sensor, and a good bit of the hose connections are tucked in behind the passenger headlight. A little tricky to access.

On Brenda's old 96 Cougar, replacing the purge flow sensor fixed the problem, at least for several years. Then the CE light came on for the same thing for a couple months, then went back off! That is one flaky system, on all cars.

Sorry to hear you have to have an OBDI car smogged. Most states just have visual for 95 and older.

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post #7 of 9 (permalink) Old 04-05-2016, 03:19 PM
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I seem to recall Swanny doing a write-up on how to change all of the vacuum hoses..

Ah, yes..Click Here-->> MN12 4.6L Vacuum / Emission Hose Replacement








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post #8 of 9 (permalink) Old 04-05-2016, 06:32 PM Thread Starter
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They said it has a nasty leak so maybe cracked hose?
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post #9 of 9 (permalink) Old 04-05-2016, 11:23 PM
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Quote:
Originally Posted by T6Rocket View Post

Sorry to hear you have to have an OBDI car smogged. Most states just have visual for 95 and older.

Al
All 1994 Tbird/Cougars with the 4.6 are OBD2. All 1975 and newer vehicles are required to test for smog in California. Its not that big of a deal, if you drive a car that doesnt pass smog, its probably a piece of shit anyways.

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Originally Posted by Slow94lx View Post
They said it has a nasty leak so maybe cracked hose?
You said they hook it up to the gas cap and pump it up. They test the gas cap and EVAP system seperately, they are both vacuum test, you dont pump it up, it gets pulled down. The EVAP test requires the smog tech to pinch off the vacuum hose to the charcoal canister to the fuel tank while the test is performed. A lot of smog techs I know wont even bother with the EVAP test, they just pass it instead of bothering to pinch it off. More than likely a cracked rubber vacuum hose like mentioned above, I would start at the engine to the hard line that runs alone the passenger side inner fender down to the air filter to the charcoal canister which is located beneath the passenger side fender / front headlight area. If its not there, the gas tank - only way to be 100% sure without tracing the line back is to perform a smoke test. Good luck with your search.
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