P0171 too lean bank one

Hey all, so I have a 98 4cyl and it threw this code a couple months ago. Runs and drives fine so it never posed a problem for me, until I had to go get it emissions tested to get new tabs and it failed due to that computer code. I am not a gear head and need some advice on where to even start to fix this problem. Any input gladly accepted on this as I need her for my DD in a couple days. Thanks!
Taco in Tacoma.

 

Well....excessive O2 is reaching the sensor. Cant determine much more than that with the info you've provided.

They should have given you a ASM printout. If they stopped before even running the dyno, they ripped you off for the fee without giving you a report that would tell you exactly what the issue is. Whether the excess air is being introduced pre combustion or post combustion will determine what the next course of action is.

 

too lean is most likely maf sensor or o2 sensors. allthough maf sensors usually pop a maf code. looks like stealership diag is in order.

 

P0171 is usually a vacuum leak

 

Too lean is most often a vacuum leak, not a bad maf, not a bad o2 sensor. The code only tells you there is an issue, it can't tell you what the cause of the issue is. And it only tells you there WAS an issue, not that it's ongoing.

 

99% wrong

75% wrong

87% correct

 

If i had a nickel for every time an O2 was blamed for doing its intended purpose, I'd be a multi millionaire

 

lol so I should have said "most often" and not "usually"?

I've only got my experience with a P0171 code that wouldn't go away, I had 2 service departments tell me that they usually find a vacuum leak somewhere that results in the P0171 code. They couldn't find one on mine so over time we replaced my MAF sensor, o2 sensor, A/F sensor, spark plugs/wires and it still didn't solve the code. Fortunately my (overpriced) aftermarket powertrain warranty came in handy and covered it all. Finally figured out that the EGR port on my supercharger was improperly capped and creating a vacuum leak...re-capped it and code gone. Was frustrating how simple it was after all the headache it caused.

 

@Misplaced Nebraskan didnt you have this code recently?

 

Yup. Cleaned MAF and connector and added dielectric grease. Cleared code and been good for a few days now.

 

Why did you add dielectric grease.

 

Yep.

 

Connector (inside) was a bit dirty from playing in water this past weekend. Added a small smidge around the outside areas to help seal it better. Pretty sure the main reason for code was dirty MAF, but figured while I was in there I'd seal it a bit.

 

OK, that's what I was hoping you would say. Most people put that stuff all over the contacts themselves, not understanding that dielectric grease is meant to prevent conduction, not improve it.

 

That would make for a more frustrating troubleshooting

 

I had that code for the longest time. When I was getting a part at the dealership, the parts guy told me to make sure that I tighten my gas cap a couple of turns after the clicking. It worked. I haven't gotten the code for over a week now.

I asked him about the gas cap "going bad" and he said that it happens. I looked at the rubber ring on the cap, and it's cracked in a few spots. So I may have to get a new one. Toyota wants $33 for a new one! Fuck that.

 

Weird...the code that pops up for the gas cap being loose is usually an evap code P04XX or something like that. Not P0171...but hey if it worked, it worked. Keep an eye on it though, every time I reset my P0171 code after attempting a fix it would come back about a week or so later.

 

A few weeks ago, I had the shop do a smoke check for a vacuum leak (P0171), and they couldn't find one. They even felt bad for not being able to find a leak that they didn't charge me for the diagnostic.

 

So, I'm back and so is the CEL... P0107. Guess me resetting it is what cleared it for the few days that it was clear. I'll have to look for a bad vacuum line or something next.

 

No exhaust leaks?