My 1997 Ford F150 4.6 failed the California Smog for the first time. 160K miles. My HCs were over maximum and COs were high. The technician said the engine was burning too rich. Some of my mods include Air Force One intake, magnaflow exhaust, bosch fuel injectors(I think injectors are same a stock size), and new upstream O2 sensors. I would like to fix the problem and not some temporary fix to cheat the test. Any suggestions would be much appreciated.
I suspect this is not a new problem. The previous smog test just barely passed.
Truck seems to be working fine otherwise.

 

what's wrong with cheating to pass a test?

 

Even though this is Texas' guidelines for failing smog, it's the same premise.

http://www.txdps.state.tx.us/vi/Misc/faq/faq_asm.htm

I guess you have to dyno your OBD2 vehicles? Texas just pretty much checks for a check engine light and off from there.

Anyway, read on.

 

Your EGR may not be working, and the Catalytic converter could be toast, but they can both be checked. A vacuum leak would also cause a problem.

 

How do I check the Catalytic converter? If the Catalytic converter is toast would it throw a code? I currently have no check engine light on.

thanks

 

Fuel pressure or the regulator may be faulty.

 

The smog shop didn't give you a list of things to fix?

 

No, the smog shop did not give any possible solutions. The tech said I should take it to a shop that can test all the sensors.

 

A shop can test the Catalytic converter and Oxygen sensors. But a dirty EGR valve and bad catalytic converter could cause your problem, I would get the EGR checked out first... then go from there.

 

Take it to another shop. Try one of those places that advertise "pass or don't pay".

 

The shop I went to is offering one free retest. It is up to me to get it fixed. For this particular smog check, I am required (by the state) to take it to a "test only station". These stations are not allowed to make any repairs.

Looks like I will need to take it to a shop that can diagnose it.

 

You can rule out the intake & exhaust. And if your EGR were suspect, NOx should be affected but you didn't mention that. I'd look elsewhere first.

AlfredB18, CA puts the car on a chssis dyno and takes readings at two "vehicle" speeds.

Doug, let's break it down:
High HCs and COs means that you aren't burning fuel efficienctly, so the rich diagnosis could be possible. It could also mean that the catalyst isn't working as well as it should. A bad cat *should* throw a code. You can get Magnaflow high-flow cats for less than $100 each on Ebay.

You state that you "think" the injectors are the stock size...this could be a big deal, if they are flowing more than what your ECU thinks. You need to make sure that these are the correct injectors for your vehicle. Too large = too much flow = rich.

The MAF and the O2 sensors help the ECU regulate the A/F mix. Since your O2 sensors are new, what about your MAF? How old is it? Ever clean the element? A fouled MAF may not always throw a code, but could be out of spec enough to give your ECU a false reading on the amount of air entering your engine...which could make your engine run rich or lean. A reman. MAF is about $60 at AutoZone. A can of MAF cleaner is $4.

How about spark plugs? How old are they? Bad plugs *should* give you a misfire code...but if they're old then I'd change 'em. Cheap and easy to do, and part of any good maintenence plan anyways.

Could be a vacuum leak...check all of these hoses and connections.

As with most things, start with the easy/free stuff first.
And buy yourself a code reader...best $50 you'll spend, and it'll tell you exactly what's wrong...versus paying a shop to throw money at a problem.

Let us know what you find.
Good luck.

 

oil and filter change and a pcv valve..octane boost couldn't hurt either