'88 F150 5.8L 4x4



Entire exhaust from the manifolds back replaced 2 years ago. The last two years it has passed with flying colors.



It failed today.



HC standard is 220. It read 1879 at high speed and 543 at low speed.

CO standard is 1.20. It read 2.69 at high speed.



Passed all other readings.



Any suggestions?

 

Mine was failing with ~600 HC ppm and ~1.8 CO%.

I took it to an exhaust shop to get a new catalytic converter put on. At the shop they said the cat on there looked relatively new, but was undersized and cheapo. After having it replaced with a new, quality cat, it passed with 15 HC ppm and 0 CO%.

Edit: I should mention though that mine was only failing at idle, at 2500 rpm it just squeeked by even before the new cat.

 

You might want to take a look at your o2 sensors as well, make sure they are reading within spec. I come across a lot of cars with their sensors biased lean causing the computer to add more fuel. The result is bad gas milage and high HC. Your cat could be part of the problem because even if the engine is running rich usually the cat will help to mask that by burning off a lot of the fuel. Do you have the other readings as well (o2, co2, and nox)? Those would help us get a better idea of what is going on.

-Jon

 

After a tune up I failed again. Here are the readings.

High RPM
HC standard 220 current 1692
CO standard 1.2 current 2.65

Low RMP
HC standard 220 current 746
CO standard 1.2 currnet 1.8

High RPM numbers slightly lower, but Low RPM numbers considerably WORSE.

????????????

 

in md at an advance auto parts i stumbled across this stuff that says it guarantees a pass at an emissions testing as long as the exhaust system is not altered you pour it in your tank, let your tank run almost dry and then fill it up and go to the test, look into that

 

i am an emissions inspector in GA, HC is unburnt fuel coming through the emissions and CO is burnt gas, so your truck is dumping way to much gas into motor

if it is carb, the adjust the settings for overall fuel/air ratio

if it is EFI then check the 02 sensors and the EGR valve, also
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