Hey all, I'd really appreciate some help!!

Picked up a used 2006 F250 4x4 with 5.4 Triton. I'm having problems passing emissions (smog) testing. It is failing HC at IDLE only.

I was getting an O2 sensor code, so I changed the sensors after the cat, but left the upper sensors. I'm now getting P0420 and P0430 codes that I wasn't getting before I changed the lower O2 sensors.

I had it tested today, everything passed but the HC on low idle.


2500 RPM:
HC Limit 200 - Read 137, PASS
CO% Limit 1 - Read 0.54, PASS
RPM Limit 2250-2750 - Read 2403, PASS
Dilution % Limit 6, Reading 14.7 PASS

Idle:
HC Limit 200 - Read 300, FAIL
CO% Limit 1 - Read 0.44, PASS
RPM Limit <1250 - Read 696, PASS
Dilution % Limit 6, Reading 14.7 PASS

I've been told to change plugs, which will cost $800 and to change the cat, another $1200. I'm hoping to not spend $2000 to pass an e-test!!

Please help!! My temp permit expires in a few days.

 

Where are you at that they do the tailpipe test?


Need the ACTUAL code to see if you actually did anything useful.

Need to know if the F250 is OBDI or OBDII, check the emissions compliance label on the underside of the hood.

Mileage?

 

Thanks for the reply.

The original code was a P2270. OBDII.

I'm in Ontario. I believe they do the two speed idle test for my weight class.

125,000 miles.

It it helps, the truck was tested in 2015 and had 35/38 HC levels. Also had 0.1/0.2 CO% levels. Both have gone up however the CO is still passable.

 

Have you cleaned your throttle body at all? If not remove it and clean all the gunk sometime the throttle plate don't close all the way and give false readings and throws O2 sensor codes.

 

Thanks, I'll try the throttle body. I used a can of sea foam the other day, but it didn't improve test results. Anything else you could recommend cleaning while it's pulled apart?

 

Focus on the HC. Cat is still working. Fresh oil and filter, change the plugs if you detect a miss at idle. Check for vacuum leaks. Anything that causes a slight misfire at idle will cause HC to go up.

Any sticking injector will cause problems too.

One more time: Seller is supposed to smog BEFORE the sale*. Lots of threads like this one, I hope you can fix it.

Edit: That's CAlifornia rules, OP is in CAnada, I saw that CA and jumped to conclusions. See post 5. Either way, IMO, if it has to test, a passing grade should be required before passing the cash...

 

Thanks. Good to hear about the cat.

I did oil, just ordered a broken plug puller from Amazon, will do the plugs this week.

I'm not experienced in finding vacuum leaks, but have been doing research and will try.

Going to get injector cleaner. Any recommendations on the best way/product to clean injectors?

Here in Ontario, it's the buyers responsibility to smog/e-test. Seller told me it was done in August. I really should have checked as it was done, but it failed the test!! Lesson learned..

 

Does it run rough at idle?
Have you checked/changed the IAC?
The IAC allows more air to get to the engine at idle when the throttle plate is closed which affects the air/fuel ratio.
Here' more info - https://www.2carpros.com/articles/ho...ol-valve-works

 

Ok, it failed again. Almost the exact same smog specs. It is still high HC on idle. CO is still low.

I did the plugs, replaced COP boots, cleaned the air intake manifold (it has no IAC).

I replaced the lower O2 sensors, but didn't do the uppers before the cat. It's also getting P0420 and P0430 codes. Could the upper O2 sensors cause this?

The upstream sensors are bouncing around between 0.1 and 0.9 volts.

 

The lower O2 sensors have no effect on HC at idle (or any other speed, for that matter) and do not cause cat efficiency codes to appear (except when then they're doing their job).

They're supposed to.

 

Ok thanks. I knew they were supposed to bounce, but didn't know how much. Won't be replacing any more sensors then!

Trying to figure out what to do next..

 

Both the upstream and downstream sensors are bouncing around together. I read that the downstream sensors should have a consistent reading and not follow the upstream with a good cat. Is this true?

 

Dead cats. They aren't doing anything. Perhaps they were gutted by a PO.


Somewhat. The ratio of upstream vs downstream switching in a properly operating system should be significant. When the ratio drops below a certain level, it's assumed the cats are no longer effective for their purpose. If the switching ratio is 1:1, they aren't doing anything which means they're either missing or totally dead.

Since the cats are not working, that's probably why you're failing your tailpipe sniffer test.

 

Just jumping back in here. The cats job is to reduce CO. His CO is OK. How could he have a gutted cat? Maybe a weak cat, but good enough to do the job on CO.

 

Control of CO (if present in the exhaust stream) is indeed one of the functions of a three-way catalytic converter which is what this truck came from the factory equipped with.

What are the other two?

When the upstream and downstream O2 sensors are switching at the same rate, the converter is non-functional.