Hey guys!
I am a brand new member. My 1995 F-250 with a 460, Auto, and four wheel drive has 225,000 on it. I just purchased it and it appears to be running correctly BUT my CO emissions came back at 3.86 at idle and 4.43 at 2000 RPM and they want me to not exceed 1. I have new Motorcraft Cap and Rotor, New Motorcraft Plugs and wires, and I am getting decent fuel mileage for the truck. I would guess the fuel injectors are factory and so is the catalytic converter. Any thoughts on where to start? My Hydrocarbons came in at 182. Thanks!

 

Those CO numbers are extremely high! Even with no cat at all, they shouldn't be that high. Just for reference, my 96 with 7.5L and 200k miles and original cat passed CA smog last year with 0.1 on idle CO and 0.0 at 2500RPM. Something else must be wrong. If the truck is otherwise running and driving fine, my first guess would be an O2 sensor problem not allowing the truck to go into closed loop. Now you might need a new cat as well, but I would start with checking the O2 sensor.

 

Thanks! It appears that the Cat was replaced a long time ago when they replaced the exhaust and I just replaced it from the Cat back as it was toast. I will start with the O2 sensor and might just toss a cat on it for good measure. It was on my list to replace anyway.

 

check that base timing is set at 10*, and have you checked for codes, even if check engine light isnt on, could have stored codes, make sure that truck is operating temp before checking for codes

 

I will double check timing and there is no check engine light that is on. Just changed plugs and they were worn but looked clean. I will double check for codes as well. I completely forgot this old system might have something in it without a check engine light. Thanks!

 

If CO is high but all other parameters are within spec and the engine runs fine the Cat converter is suspect. If both CO and hydrocarbons were high it would be safe to assume the engine is running rich, but the fact you get "decent" fuel milage from a 460 that doesn't seem to be the case.

 

Thanks! My Hydrocarbons needed to be under 220 and they were at 182 so they were in spec. Looking at my converter I would guess it has over 100k miles on it as it appears it was put on with the exhaust I had pulled off that was super rusty and worn out. Typically in our area it takes 150k miles to look that bad.

 

For what it’s worth, I worked as a tech at a shop that did smog checks for several years. Since I had access to the machine, I actually did emissions checks with the machine on my well tuned 63 Galaxie and 73 Ford LTD just for ****s and giggles. Both those cars with no emissions controls or CAT came in under 2.0% CO. Your truck is running too rich plain and simple. There is a problem with your fuel Injection system. The fact that your HC are passing but your CO is so high is somewhat bizzare to be honest, so I’m not sure what to make of it other than your truck must be running pig rich but not misfiring and somehow your CAT is Cleaning up the HC but not the CO as much.

A brand new CAT can work wonders and might hide the symptoms and get you through smog, but it is not the underlying problem. And a truck running that rich will foul a new CAT soon enough. Diagnose and fix the underlying problem and you will save yourself a lot of money. Your CAT might be just fine.

P.S. I’m not sure I’ve ever heard of anyone getting “decent” fuel milage from a 460 lol. Those are generally not words I’ve used in the same sentence. I guess it’s all relative...

 

going off what conanski/geoffunkel, said, you could have continuous memory code, O2 sensor for system rich.

 

Yeah, anything above single digits...

 

I agree you should fix the underlying issue before you sully your expensive new cat.

-O2 sensor is prime suspect.
-Check EGR, MAP, ECT and vacuum lines next.
-Pull codes

Finally if you need to pass emissions in a pinch run the fuel tanks almost empty and add some "guaranteed to pass" snake oil, get the engine really HOT , pull the SPOUT jumper just before testing and then get it tested right away.

 

This might shed some more light. Sandy
Common Reasons for Failure | EnviroTest

 

Thanks guys! Diving into it tomorrow. Ran the codes this afternoon and got a TPS error #23 and a EGR malfunction with a #33. Going to check timing as well.

 

T-stat working, getting you to high enough operating temps?

 

A 1995 model year F-series truck should display three digit codes. If by chance your truck has a C6 transmission it may display two digit, but not likely.