So, over the past couple of weeks I have been trying to get rid of the above codes, Here's what I've done.

Changed fuel filter
2 bottles of injector cleaner
tune up(plugs wires cap rotor pcv)Did this step because of another code(don't recall the number but it was a misfire in cyl 6)

After all of that I am stuck, the MIL is back on after just a few miles, and It is still missing intermittantly mostly at highway speeds.

What's next? Injectors? commercial grade injector cleaner(jiffy lube?)

Its a 96 4.9l 5speed with 225k on the ticker

Greg

 

Key in on things that will impact both banks. I had this same problem on my daughters 95 Mustang (3.8). I found a couple of vacuum leaks, but that didn't fix the problem. I noticed that the Baro reading was reading like we were at around 5,000 feet, but we are close to sea level. I cleaned the MAF and the Baro reading corrected itself. The codes have not been back!

Smitty

 

These codes are telling you the computer has made as much adjustment as it can but the right side O2 sensor still isn't switching, this probably means the sensor is bad if there are no other codes. If you had codes indicating both banks were at adaptive limit then I would suspect a fuel pressure problem or blown FPR but that's not the case.

 

Correct me if I'm wrong, but P171 AND P174 means both banks are lean... Since the likelihood of both sensors going bad at once is pretty slim - so a fuel delivery problem is more likely, yes?

I'd second checking the fuel pressure and pressure regulator...

 

Yes.. '96 F150 is OBD-2 which makes a difference.. I was looking at OBD-1 codes.

 

Found 2 vacuum leaks today, and repaired...seemed to help a little bit, but we'll see if the code returns.

Greg

 

Hey glkearns we got the same problem same year what the hell I pulled my back tank and bad fuel pump and toss it behind the shed and rerouted the plumbing still a low pressure on the injectors so says the mechanic at the shop now I have to replace the other fuel pump it's always something let me know how you solve your problem.Thanks

 

Check your vacuum lines. My codes havn't been back. Now I am just waiting for all the self checks to get done to pass smog. I'm changing my t'stat out tomorrow (back to a 195 deg from 160 deg) apparantly it's not exiting warm up and the computer won't complete the self tests without...If that's not it, I start changing o2 sensors.


greg