Just adding this in case someone else might have this issue. I had a code 172 (oxygen sensor indicates lean mixture) and replacing the oxygen sensor fixed it. 93 Ford F250, 7.5l (460)

However, the condition that failed this oxygen sensor was ironically an overly rich mixture. Didn't find out until recently that my fuel pressure was 20 psi over the specified 30-45 psi (measured 65 psi). A failed fuel pressure regulator caused the pressure to be way to high. For years the truck would idle rough and you could almost taste the gas coming out of the tailpipe. These years of the fuel pressure being too high caused the oxygen sensor to become caked with carbon deposits and eventually caused it to fail. I am actually thankful for the code, because otherwise I probably would not have found the fuel pressure issue which was the true cause of the code.

I highly recommend spending the money for an emissions manual. Went through it step by step for code 172 and found the fuel pressure issue pretty quickly.

 

Awesome to hear you identified and fixed a pretty severe issue..

One thing is you may have to change the cat or do the reset process if you still keep getting codes or if the new o2 sensor turns up defunct due to fuel being imbedded in the bottom of the honeycomb inside the cat that still has to get out so while scavenging back the rich mix back from inside the cat affects the 02 sensors readings......

I actually had the inside of my cat meltdown after my FP reg diaphragm busted and the fuel pump force fed into my engine through the vacuum line completely full of fuel from oilpan to out the airfilter tubes from the plenum overflowing...The ear deafening backfire produced from the exhaust system being filled too blew the muffler clean off practically I had to cut it off with a saws all.....Then I had to gut the cat when it melted down inside after I fixed the regulator and drained all the fuel.....LOL

I clean my 02 sensors in a shotglass full of Lemon juice overnight....Then rinse it with a lil non chlorinated BP cleaner or 100% pure stove alky then burn it dry with a plumbers torch.........

You can use same torch to test them too using an infrared temp gauge and a DVOM...

The hotter you get the tip of the 02 sensor up to 1200 degrees the higher the voltage they emit from 0-1v that can be read by a DVOM..

One thing and proper practice is to bleed down the EEC for 20 mins restart induce a full load 2 mins idling turn off load after 2 mins and drive moderately for 10 miles to set fuel and spark tables correctly...

Also make sure your distributor is set to 10* btdc and reset the timing advance by pulling and reinstalling the spout connector...to do the spout right,,bleed down battery 20 mins,,disconnect the spout module,,start truck then induce full vehicle load with everything equipped in the vehicle turned on and set to high for 2 mins to calibrate load draw and sync sensors then shut the load down and continue to run truck to operating temps,,check and adjust timing with a timing checker set timing to 10*BTDC shut truck down reinstall spout and then restart truck and drive the truck 10 miles moderately to reset the eec.........

Resetting and relearning should be done every 3500 miles...The EEC memory is only so large and when it gets full it lets you know with running issues too.........

Take care and awesome job getting your problem figured out and fixed.................

 

codes dont always mean that part is bad, it gives you a starting point, to check, sensors in that area, a bad exhaust gasket, will make the O2 sensor give you a lean code, because you are introducing unmetered air in front of the O2 sensor.

 

Thanks SurgeMaster. Didn't know about that re-learn procedure. The code has been gone for awhile now. Wanted to make sure it stayed off before I posted. You just always see these posts with a problem, they get it fixed, then never post a resolution. Luckily I think the CAT is still pretty good. I couldn't smog the truck until I got the CEL fixed. After replacing the O2 sensor, I smogged it shortly after and the numbers were super clean.

 

New member, new question:

Sorry if I am running counter to group etiquette here, I can's find a place to start a post, only a "reply"... here goes.

So I have a 1994 F-150 XL 5-speed and I-6 motor (1-year now) and I absolutely love it. Stock tires are the 235/75R-15. I joined Costco for a deal on hearing aids and discovered they have good tire prices. I wanted Michelin but they don't make 15" tires anymore. I'm looking at buying new wheels, 16" or maybe 17" (if not too large), depending upon what the wisdom of this group is. I found that Dodge Dakotas run the 5x5.5 bolt pattern in a 16x8 wheel but the offset is +25mm. I think stock F-150 in this year had a -44 to +44 mm offset, which must mean zero offset? That's one question, is that true, zero? Let's say it is zero offset, would a +25 mm make the wheel poke out a little more than OEM? And one last question, would 17" work and be desirable, not too stiff since the sidewall would have to be shorter.

thanks.... tgrizzle

 

It’s right here

 

Dang, it was so obvious I missed it. thank you