This is an interesting issue, I have worked on cars for years but this is weird. Every time we open gas tank to fill it with gas any amount a day later the car sets a code, of PO171 and freeze frame data stating car is not moving when code is set. So, it make car rich and causes bad smell in exhaust. It say card is lean in Bank 1.
Here is the kicker I reset the code and it goes away for weeks, until we put gas in car. There are no pending codes after the code is set. What is going on here? Anyone have an idea, I replaced o2 sensor, Map sensor, and a bad o2 sensor after the cat which have all improve the performance of car. Please help.
Thanks Phil
I have asked many questions to solve this code, it took me months to find someone with a solution most were wrong, including on this. I solved it by finding that there is something called no code hidden or secret relocatable vacuum leak. undetectable by computer since its so small. This is the BRAKE VACUUM BOOSTER. I way I think I prove it was bad was when pressing on power brake while car was sitting idling the mixture values would go up slowly. But, I still didn't believe it immediately. So, if you get this code, PO171 and you don't fine the vacuum leak. Amuse its the Booster and replace it. don't change out any other part.
sounds like EVAP system problem
So even if car runs fine later, after reset of code, when is the EVAP system at fault in causing engine to think its running lean? Remember it seems to set code right after opening the fuel tank so when car is stopped what is that system doing at that time.
What happens if you fill up in another gas station?
100 percent the vacuum brake booster, very small leak that caused the code
Check the ends. Prior to buying one of my "fleet" of Rav4s, the car's evap line in the engine compartment was bumped and caused a code. It could be that the change of pressures, combined with a very small leak, might be the trigger. Could also be overfilling of fuel though that's way too obvious.
I don't know if putting high-temperature grease around the connectors might solve the problem by blocking any light leaks... I have a 15-year old vehicle where the air intake connection isn't so tight and the code will appear. Solved it by putting AGP(?) brake lubricant around the connectors (being careful that it isn't introduced to the system). All is good now.
thanks, but what connectors are we talking about, and where in the intake do I put the brake lubricant around. I am also thinking the fuel pressure regulator that is very old may be causing this. Any suggestions
Although I replaced everything since car is old including the complete fuel pump assembly and MAF, fuel filter. As soon as the tank is filled up at my Costco station, a few minutes later the Lean mixture code comes up. Now all during the use of this gas after code is reset, the car runs perfectly fine, with no pending codes. Before it would come back randomly after a few miles or so. The main reason the mixture was so messed up was the cat. O2 sensor became dead no volts and I replaced it. So, I was so happy the code was gone until I refilled tank. I can live with this, but its still a mystery car issue. How do I know if it not the tank venting device, Or maybe they are overfilling tank with a bad sensor on Costco filler head. The reading on the freeze data say car is not moving, and all the O2 sensors are not providing a rich percent as the car says. CA emissions most likely now is a sensitive computer software, thank CA. The last thing to replace are the injectors since I have to remove the manifold to fix oil leak on valve rear covers. Anymore ideas anyone I am now stumped.