Question about 1990 Ford F250

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Emissions level HC (PPM) too high in truck. How to fix?

1990 Ford F-250 5.8L. Failed state emissions test. HC limit is 160, truck was tested at 169. Others that passed were- CO (%) limit 2.23 had 2.11, NOx (PPM) 2897 limit, tested at 567. What needs to be checked to get #'s down so I can pass retest. THANKS!!!C.C.

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  • Curt Downs Aug 17, 2008

    My parts store recommended 'guaranteed to pass' additive to fuel tank, and I laughed, but hey, $10 and I passed with flying colors!! countrycurt0

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  • Ford Master
  • 2,359 Answers

Do an oil change with 20W50 oil (or one grade higher) to prevent blow by during the test.

You current oil has HC from blow by though the rings.

Do a fresh oil change will lower the HC.

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Change spark plugs,wires,cap and rotor if they are over 24,000 miles
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Make the smog check appointment for the EARLY MORNING. Colder air will help the fuel burn better.

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Clean or change the air filter and pcv valve.

Clean Mass Air Flow sensor with CRC Mass Air flow cleaner or electronic part cleaner.

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Do a quick wipe down on the wires and cap to take the moisture off.

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Check spark plug wire contacts for corrosion.

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Fill the tank to around 3/4.......just in case your fuel pump is weak.

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Ran the truck for 20+ minutes on highway before the test.

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Do not carry excessive cargo on the truck bed.


These are the little things I would do to get the HC and CO down.


Please post more information on the comment window.

Posted on Sep 01, 2009

6 Suggested Answers

  • 3 Answers

SOURCE: 1994 Mazda Protege 1.8 SOHC failed emissions HELP!

have your EGR system checked . sounds to me like its not working or clogged

Posted on May 03, 2009

morse008
  • 1111 Answers

SOURCE: FAILED EMISSIONS

possible but could be head gasket or valves , or worn rings and is by passing the pistons going straight out the end ...or maby settings are wrong ? try carb cleaner and inspect visually air-filter etc.

Posted on Aug 26, 2009

  • 35 Answers

SOURCE: volvo 850 wagon failed NOx emissions test - badly!

Hey Pitloops!
It seems likely that one or both of your o2 sensors are acting up, or that your engine is sucking in unaccounted air from a leaking vacuum tube. Spray the tubes with "start gas" while the engine is idleing. If you hear it revving up when you spray the gas on the tubes you'll know there's a leak.
I'll sacrifice a squirrel for you and hope that the problem isn't your o2 sensors since they can be expensive to replace. Fcpgroton.com is probably the cheapest part supplier online if you'll need new sensors.
You might also want to clean your throttle body, as it usually gunks up with carbon deposits and sludge over the years. It only costs you the price of the carb cleaner to do it and the car will probably run better afterwards even if it doesn't solve the problem.
Good luck!

Posted on Jun 27, 2009

  • 15 Answers

SOURCE: Emissions failing with high NOx

You need to check the oxygen sensor. You car may be running lean and therefore giving you increased NOx levels

Posted on May 30, 2009

emissionwiz
  • 63456 Answers

SOURCE: lowering the HC ppm reading for emissions

change the oil just prior to test, run the engine at very high idle just prior to test to super heat Catalytic converter, this will lower reading as much as 100 PPM.

Posted on Aug 14, 2009

6ya6ya
  • 2 Answers

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Posted on Jan 02, 2017

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First, thank you for asking me for my input on this. It just so happens, that I used to own a Ford ranger that had the same engine as yours. It was a 1990, but there are few changes to these model years.

Anyway, there is only one reason that your HC levels would be high. Your engine has WAY too much unburned fuel in the exhaust. The same reason applies to high CO levels. Too much fuel and/or not enough air.

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