P0174 code engine running too lean

Ok so about a week ago I decided it was time to clean and re oil my air filter. This is the first time I have done this (50,000) miles. After I did it everything was going fine then yesterday. I had a couple of 5 gallon jugs with gas that I got for the jetskis but didn't end up using. They were about 3 weeks old and I hadn't put any stabilizer in them so I decided to put them in my truck thinking they wouldn't have gone bad yet. Then backing out of my driveway starting to accelerate it was really sluggish and slow to get going, which caused the check engine light to come on. I went straight to the station and topped it of with premium gas and that helped. I have since run that tank through and filled up again and the truck is running fine now, but the light is still on. When I finally got around to pulling the code tonight P0174 is what I got. Can bad gas cause this, or would it be something related to the air filter. I had read about the oiled air filters causing problems with MAF sensor. Should I just clear the code and go on with it since the truck seems to be running fine now? It really seemed like it was the gas being bad that caused this, but i had never heard of bad gas throwing a code on a car. Thanks for any help.

 

I dont have 2nd gen, but I can give you my experience with the system too lean (P0171).

I too have a K&N filter and after an offroad trip, I started randomly tripping the too lean code so I figured it was just the filter got too dusty (even though I'd think it'd be a low air flow code if that was the case), but I cleaned it anyway even though it had only been about 3 months since the last time.

Anyway, since I have a scangauge, I'd just reset the code when I'd see it pop up. The first time, I went about a month after a reset and I cleaned the filter. Eventually, it showed up again and I'd reset it. After a while it got to the point it was tripping about every 20 miles. The truck still ran great the whole time.

Right now, I'm at the point that I cleaned my MAF and it hasn't tripped since, but I've only put about 100 miles on since I've cleaned it.

With your K&N filter and my own experiences so far, I would highly suspect your MAF is just dirty. It is definitely the easiest step in the diagnosis process to fix, but depending how often it trips, it might be a long process before you know for sure if you fixed it. I'm really unsure if this code will clear by itself, so you may want to clear it manually.

I also ordered a AFE dry filter to replace my K&N filter, but I'm also going to move away from the CAI system and put the factory one back in with a deck plate mod. Kinda want to get away from the oiled filters for the above reason.

 

Thanks, I just cleared the code and if it goes off again Ill try the cleaning the MAF. I too think I may get away from the oiled filter if it causes this many problems.

 

Well, I dont think it really causes all that many problems, as I'm sure you've had yours on for years and mine has been on at the very least for 2 years, probably closer to 5 and this is the first I've had a problem with it. Just add spraying down the MAF with cleaner to your yearly maintenance (or spray down the MAF when you clean your filter) and I'm sure you'll be ok with the K&N if you like it.

I'm also thinking of putting in a snorkel, so dont have much of a choice but to get away from the cylinder type open air filter.

 

I'm having this same issue right now. The check engine light came on and I was pulling codes P0171 & P0174 but I cleaned my MAF and now I'm only pulling P0174. I checked all my vacuum lines and they seem fine...the structural integrity of them look good and all the hoses are connected properly. I'm wondering if I have 1 or 2 bad O2 sensors

From my research these codes have to do with air to fuel mixture hints the "Running Lean". I guess my problem could also be a bad fuel filter or fuel pump....I'm kinda lost right now. I'm gonna have to take Blue in to get looked at.


Any body else have any thoughts??

 

The P0 codes that have been listed, P0171 left bank lean (driver's side) and P0174 right bank lean (passenger's side) both have a common item to check. The front O2 sensor that should be on each exhaust side of the V6, before the catalytic converter. On most diagnostic guides, the first item to be checked is the O2 sensor, because it the most likely item to fail first and cause the P0 code to appear.
False readings from this sensor will make your computer lean out your fuel mixture or make it read too rich and kill your converter. Too lean and you can fry your pistons, so you need to either check the O2 sensors or replace them.

 

I lucked out...it was my MAF and it was still under warranty from Checker....replaced it, cleared the codes and I'm good again. I noticed a significant difference in my truck response too! Its not all sluggish anymore at highway speeds

 

Hello Everyone, I know this is an old thread and I'm not sure if I'll get a reply but it's worth a shot I guess. I have a PO171 & PO174 code on my 2015 Toyota Tacoma (4.0 V-6). I've replaced the MAF, had the engine tested for pressure (which showed to be all good), and filled the system with smoke as to find any potential vacuum leaks. I didn't find any leaks in the system and the replacing the MAF didn't do anything. I also tested the ignition coils (no issue found), cleaned the throttle body, and fuel injectors which seemed to help for a few miles but then the truck went back to driving sluggish. It seems like my Tacoma drives great at certain times but other times will shake as if it's about to shut off similarly as if a vehicle is running out of fuel. The mechanic who tested the fuel pressure for me said it couldn't be the fuel pump because the engine pressure was good. I'd also like to mention I had additional codes which may have relation to the ones mentioned: 01604 Startability Malfunction, P1605 Rough Idling, P219A Bank 1 air-fuel ratio imbalance.

From reading everyone's comments it seems like a possible solution is replacing the fuel rails, replacing the fuel pressure regulator, and eventually the screen filter/ Fuel pump.

Pls help.