I just used a Sunpro scanner on my 1993 Pace Arrow motorhome with the F53 chassis, 460 engine. The "check engine" light was coming on, and staying on, after about 30 minutes or 30 miles.

I had no codes during the KeyOnEngineOff test.

I had a code 173 during the KeyOnEngineRunning test. The Sunpro book says a code 173 is "Heated exhaust Gas Oxygen sensor voltage signal indicates rich (Bank #1)".

I already suspected that the engine was running rich, beacause it spits out black "goop" when cold and the fenderwell where the exhaust exits is somewhat blackened from the exhaust. But the engine runs fine and idles smooth as a kitten.

Any ideas on what to look for to make the code 173 go away?

The 02 sensor, catalytic converter and ECM (subjects of a Ford recall), EGR valve, plugs/wires, dist cap/rotor, fuel filter, air filter, breather filter, and PCV valve are all new.

Could my Code 173 (and my symptoms) be related to timing that is too advanced or too retarded? I'm not familiar with timing adjustments and do not have a timing light.

My son, who is an excellent mechanic , (he is in USAF and works on F-16s) says he can check/adjust the timing by ear? But he also says that serious engine damage can be caused by incorrectly adjusting the timing. This has me nervous, because I can't afford a new engine.

Thanks in advance for any thoughts on how to narrow the focus of my search.


Tom Norman

 

Check the fuel pressure and the fuel pressure regulator to make sure they are within spec - 35-45 psi if I remember correctly. I don't think the problem would be timing related.

 

My son and I just resolved the code 173 that we got when we hooked up our code scanner. Turned out to be a bad fuel pressure regulator on the injector rail. The rubber diaphragm inside of it had failed, allowing raw gas to be sucked via the vacuum line into the intake. We just finished putting in a new one, Sorensen part number 800-127, from Advance Auto Parts ($23.99). Our code 173 is now gone! No codes at all. Plus our engine now runs smoother than it has ever run.