mthinkley Posted April 14 Share Posted April 14 My 2015 mkz 3.7l has 90k miles and threw the p0171 and p0174 code. After watching many videos I have begun the process of elimination. The long term fuel trims are +30. The short term fuel trims are in normal range. I've tested maf, fuel pressure, smoke tested for vacuum leaks, changed all four O2 sensors, air filter new, pcv valve, purge valve. I'm out of ideas. I have heard that if someone ran E85 fuel it could created a problem like this. I've added 3 bottles of injector cleaner to the last 4 or 5 tanks of gas. Any help would be appreciated. I'm stumped Quote Link to comment Share on other sites More sharing options...
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