I have had an ongoing problem. I have had the codes 171 & 174 for the last few months. I got printouts for these codes, and replaced first the MAS, then the 3 oxygen sensors. I reset the computer and still get the codes. sometimes it is only 171 after reset, other times it is both. One of my mechanic friends said I probably have a intake gasket leak. Is that the next most likely cause?
Check Engine Light still on on 1997 Ford Ranger
it is such a shame that you had to spend so much money and not have your problem repaired. You could very well have an intake vacuum leak. Check your Long Term Fuel Trim and compare banks. If it is an intake leak, one side will be higher than the other. Also, the injector pulse width will vary by 3-4 milli seconds bank to bank, because one side is allowing more air in than the other due to the leak. Be sure to check the manifold, if you take it off, to make sure it doesn't have any leaking areas in any of the runners and where they join the plenum.
I also have a '97 ranger with a v6 and had the same codes coming up. I did all the checks, replaced maf, redid intake gaskets and injector o-rings. NOT my trouble. My problem was a hole was rusted in the pipe going from the egr valve to the intake plenum. It was right behind the valve on the bottom side of the pipe. I had to use a small mirror to see. I found it accidentally. I repaired the pipe and all has been fine since. An intake leak can come from any area where there is suction from the intake.