Failed Emissions
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Junior User
Joined: Jun 2002
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Failed Emissions
I live in Murfreesboro, TN. My 84' Ford F-150 with a 302 failed the emissions test. It showed a reading of 284 hc. Maximum is 220. Also on my receipt is says my truck has 40,000 miles. The truck has 140,000 miles (mis communication). Would the mileage have anything to do with the test? Why did it fail? It passed last year.
Moderator
Joined: Jan 2001
Posts: 56,949
Likes: 2,718
From: Virginia
Failed Emissions
Causes for high HC could be:
miss firing
running too rich.
I would replace the sparkplugs and check the sparkplug wires. Replace the cap and rotor. If it seems to be still running rich and smells like rotten eggs, I would suspect the power valve is leaking in the carb(don't you have a motorcraft 2bbl?).
miss firing
running too rich.
I would replace the sparkplugs and check the sparkplug wires. Replace the cap and rotor. If it seems to be still running rich and smells like rotten eggs, I would suspect the power valve is leaking in the carb(don't you have a motorcraft 2bbl?).
Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
Failed Emissions
1)change the oil if it is old. Oil can feed HC back into the mixture at idle, as it can hold hydrocarbons mixed with the oil and let them out when the oil gets hotter.
2)check your thermostat. Low coolant & engine temp can cause higher HC readings.
3)check your idle mixture screws, if the failure was during the idle part of the test. (I don't know how TN does their checks). Turn them in until the engine misfires, and then back them out for smooth running.
4)check your air filter.. if plugged will cause richer mixture & excess HC readings.
5)might as well check the PCV filter thingy in the air cleaner as well
6)get the truck WARM before the test. Take it on the freeway or drive up and down hills for 15 miles before going in for the test.
7)turn up the idle a smidge, until you are right under the limit for idle speed. Engines run cleaner at higher RPMs.
Your engine is REAL close to passing, so it can't be in real bad shape. It's just a few things you can do a little to no cost to make it pass.
tom
2)check your thermostat. Low coolant & engine temp can cause higher HC readings.
3)check your idle mixture screws, if the failure was during the idle part of the test. (I don't know how TN does their checks). Turn them in until the engine misfires, and then back them out for smooth running.
4)check your air filter.. if plugged will cause richer mixture & excess HC readings.
5)might as well check the PCV filter thingy in the air cleaner as well
6)get the truck WARM before the test. Take it on the freeway or drive up and down hills for 15 miles before going in for the test.
7)turn up the idle a smidge, until you are right under the limit for idle speed. Engines run cleaner at higher RPMs.
Your engine is REAL close to passing, so it can't be in real bad shape. It's just a few things you can do a little to no cost to make it pass.
tom
