P0171 Code, Not 02 Sensor

I got a P0171 Code (Fuel Lean, Bank 1). I was told it was (almost always) an 02 Sensor. I changed my 02, cleared the code, got it back later that day.

Can't find any vacuum leak.

What else can I look into, to find what is giving the P0171 Code?

This is a 1997.
Thank you,
Chris.

Check for vacuum leaks.

start by checking these things,Fuel pressure. The system will go lean if pressure is too low. The PCM can compensate for some decrease. However, if fuel pressure is too low, a DTC P0171 may be set. Exhaust leaks. An exhaust leak may cause outside air to be pulled into the exhaust gas stream past the HO2S, causing the system to appear lean. Check for exhaust leaks that may cause a false lean condition to be indicated.Mass Air Flow sensor. Disconnect the MAF sensor and see if the lean condition is corrected.Fuel contamination.poor connection at pcm.incorrect pcv valve,in some cases an aftermarket pcv valve can cause a vacuum leak,causing a lean condition.these are just some things you can check.some need to be checked with a code scanner with engine data to monitor long term and short term fuel trims.

Can I take the MAF Sensor out and spray it with carb cleaner? I read somewhare to do that, but my friend said he always herd never ever touch or let anything touch the MAF.

you can spray the maf,it will not hurt it.just dont get carryed away when spaying it.or you could remove it and check it,see if there is anything on it and blow it out with compressed air.

I may try and do that. I don't think it's the MAF tho. Wouldn't I get a different code if it was the MAF?

no you would not get a code for maf,because you have a fuel trim lean code.which means the engine is starving for fuel.fuel trim long term and short term monitor how much fuel should be added or subtracted.in this case the fuel is being added because it is seeing the minimum amout of fuel being delivered.so its tring to add fuel to compensate.as far as the maf it monitors are that is being pulled in to the engine,from there the pcm calculates the readings from the maf,map sensor the o2 sensors,as well as ignition timing and spark.by these readings it will tell the pcm what the engine is doing and the pcm will tell the engine how much fuel to deliver and how the engine should run.the only way it would set a maf code is if there was a direct problem with it.fuel trim has to do with fuel delivery.either to much or not enough.(sorry for the long story)you could also check fuel filter and fuel pressure.a plugged fuel filter will cause a lean condition as well as a weak fuel pump.fuel trim codes a very hard to diagnose.try checking fuel filter and pressure first.it will be hard to diagnose without a scan tool and without knowing what the fuel trims are a well as other impotant engine data.

Thank you for your reply. I use cheap gass. I know it's been at least 5 years since the Fule Filter has been changed. I have a friend who says he changes his every 6 months to a year.
I tried to change the filter today. When I got out, it was 27 with a very cold wind blowing. I was so cold I didn't even get the jack out.
I will try again tomorrow. Chris.

Thank you for your reply. I use cheap gass. I know it's been at least 5 years since the Fule Filter has been changed. I have a friend who says he changes his every 6 months to a year.
I tried to change the filter today. When I got out, it was 27 with a very cold wind blowing. I was so cold I didn't even get the jack out.
I will try again tomorrow. Chris.

That reminds me of the time I changed out my transmission in about a foot of snow in the parking lot where we lived in January in Michigan---NOT FUN!

Changed the Fuel Filter yesterday. Looked really old. Brown gas came out one side.
Second day I've not got the code back, but maybe I'm typing to soon. Car still runs ocationally like somethings wrong.

Didn't think I need to disconnect the battery like the manual said. While under the car, with gas all over my arm and shirt sleeve and floor, when ever the wrench touched anything, it would spark. I got up and disconnected the neg. on the battery.
Chris.

Do not use carb cleaner on the MAF, unless you want to buy a new one. Carb cleaner leaves residue that will ruin it. IF you want to try to clean it, buy specific MAF cleaner, You can also use non-residue electronic parts cleaner, just be sure that it's safe for plastics.

Update: End of 3rd day, got the code back last night. Other then starting, it runs good. Guess I'll have to start spending money I don't have trying to fix it.
Chris.

start by checking these things,Fuel pressure. The system will go lean if pressure is too low. The PCM can compensate for some decrease. However, if fuel pressure is too low, a DTC P0171 may be set. Exhaust leaks. An exhaust leak may cause outside air to be pulled into the exhaust gas stream past the HO2S, causing the system to appear lean. Check for exhaust leaks that may cause a false lean condition to be indicated.Mass Air Flow sensor. Disconnect the MAF sensor and see if the lean condition is corrected.Fuel contamination.poor connection at pcm.incorrect pcv valve,in some cases an aftermarket pcv valve can cause a vacuum leak,causing a lean condition.these are just some things you can check.some need to be checked with a code scanner with engine data to monitor long term and short term fuel trims.
Brian or whoever,

Car now every so often would sputter and not go. Today I tried to go somewhere and it quit. I tried to start it and it doesn't even come close to doing anything except turn over.

Na-na-na-na-na-na-na, nothing.

Waiting for my friend to get his Fuel presser gage. I read that you need to start the car to check pressure. How can I do it now?

Does this change anything since it won't start at at?
Thank you,
Chris.

Engine doesn't have to be running to check fuel pressure. Fuel pump runs for just 2 seconds when key is turned to the run position so you may have to turn the key a few times to see the max pressure. See if the pressure will hold for ten minutes. Also:

Check for spark at each of the three front cylinders.
Check for fuel injector pulse.

Thank you for the reply. Not sure if it can be spark, since I got a system Lean.
It's taken me a couple weeks with no luck to try and find someone with a fuel presser gage.

To check fuel injector pulse seems like it could be even harder to find.

I will keep working on it. Hope it's not a fuel pump. I have a full tank of quality gas, with a $12 techron, and some Heet added.
Chris.

This is not necessarily relevant to the lean problem, but just a general comment based upon your last statement. You mentioned that you have "a full tank of quality gas, with a $12 techron, and some Heet added."

Chevron Techron is among the better in-tank injector cleaners you will find, so that was a good choice.

However, using "HEET" in your fuel might not be helping, and actually might be doing damage. DeMert's HEET used to be nothing but methyl alcohol (methanol). Like most alcohols, it has an affinity for water, and will help keep it from freezing. However, methanol also creates a mildly corrosive acid when mixed with water, and that can be very hard on fuel pumps, pressure regulators, and injectors. Ethanol and isopropyl alcohols do not exhibit the same tendencies, or certainly not to the same degree as methanol. DeMert may have reformulated their product now that most vehicles have EFI systems, or maybe not. You might want to read the bottle to be certain.

What is worse is that you might be wasting your money by adding any alcohol to prevent freezing. Most areas of the country are now using 10% ethanol blended fuels. That means that the full 16 gallon tank of fuel you have already includes over 1½ gallons of alcohol, which is WAY more than the 6-8 ounces you are adding with a bottle of HEET. You'd have to dump in 24 bottles of HEET to equal what is already in the fuel, which would not only get expensive, but would be a complete waste of time. Save your money, and use $3/gallon ethanol blend rather than $16/gallon for HEET.

I wanted you to check for spark because it's no longer starting, not because of the lean code.
You can check for fuel injector pulse with a #194 light bulb. Just straighten the wires from the base of the bulb & slip it into one of the fuel injector wires. Watch for the bulb to pulse while someone cranks over the engine.

Thank you for all the replys.

I put the Heet in because when it was sputtering a macanic told me it might be water in the gas (and could be freezing). It got down to single digits for a while.

Someone else told me about the alcohol added to the gas. I checked at one station and they did not have it added. It may be at another I go to but haven't checked since I don't have a running car.

It was something I did just to eliminate water being in the gas, and to be able to ask him more when it didn't work.

I will keep searching for someone with a gage and post back. If anyone else has ideas, keep replys coming.
Thank you,
Chris.

After walking for a couple weeks, I went out to try and start the car. After a few trys, it started. I drove it to a friends house. When I left, it took a few trys but started. I made it home fine.

Someone told me, usually, a fuel pump works or it doesn't. They don't work intermittently.

Anyone have experience with this?