Hello everyone! I am pretty new to this site and have found the information here to be most helpful. With that being said, I have done quite a few searches for the issue I am having and have not been able to really find a good solution. So, here's a little background:

I have a '97 Ranger 4.0L 5 speed 2wd with roughly 64,000 miles on it. Back in December I came across the dreaded P1131, P0171 and P0133 engine codes and through research on this site found out that '97 Rangers tend to have issues with upper intake gaskets and fuel manifold gaskets leaking. I went ahead and replaced all the gaskets and life was good. A few months ago, my CEL came on again with the same three engine codes. So now, I am scratching my head trying to figure out whether or not I really have a bad O2 sensor or if I have a vacuum leak somewhere else. Has anyone had a similar experience? Any other advice?

Thanks,
Travis

 

Do you have an aftermarket intake? If so or not try cleaning your MAF and change you PCV valve. Also may want to double check the connections of the sensors. The engine sensor harness may be getting moisture in it. Honestly sounds like a wire issuse. I am sure more people will chime in soon

 

I don't have an aftermarket intake. I guess I should also mention that I live in Southern California so we usually don't have problems with our vehicles due to corrosion/moisture, but I'll definitely check it out.