So I got my check engine light diagnosed and came up with code p0171 and p0174. Basically says fuel is running lean. Did a little research and found out my master air flow sensor might be dirty. Cleaned it and the light came on immediately after reinstalling. Anyone else had these two codes come up? I don't think my o2 sensors are bad because nothing is coming up about those or about a misfire. Let me know if you have had these codes and what you did to fix it thanks!

Probably the most common cause of these codes is intake gaskets / vacuum leaks.

Bad Mass Air Flow sensor, just because its clean doesn't mean it's functioning correctly.

most common cause is definately the intake gaskets. If you get from aftermarket sources, felpro has 2 different gasket sets availible. Get the upgraded gaskets, or get them fom the dealer, loctite the bolts and torque to 89 inch lbs......common problem

Could it possibly be o2 sensors? That was what the guy at autozone said it probably was but nothing I have found online says it is o2 sensors because no code came up for them. Intake manifold gaskets sounds like what it is. How big of a job is it to replace them?

A weak fuel pump or restricted fuel filter will also cause lean codes. Vacuum leaks are a very real possibility and can be diagnosed by carefully spraying around the intake manifold\throttle body with carb cleaner while running, and listening for a change in the way it runs.

any recomendations on where to start?

I am thinking start by looking for vacuum leaks and checking fuel filter first, then moving on to intake gaskets and fuel pump last. I need to get this fixed so I can try and sell it and I am on a pretty strict budget.

I would spray it first to ck for vacuum leaks and if it doesn't change, either check fuel pressure or pull the filter and see if you can blow through it. Once the filter is emptied, you should be able to blow through it with very little resistance.

Sorry for so many questions but why exacly would spraying carb cleaner make it sound different if there is indeed a leak

Because if there is a vacuum leak, it will draw in the carb cleaner and the engine will pick up RPM.

so I checked for vaccum leaks, didn't have any change in RPMs, looks like I need to check fuel filter and pump now...I think I will need to wait for some help from my Dad on those two

Sell it and get something new lol. My 02 is driving me crazy now. Never had any issues the past 4 years but in the past 3 months I've had the alternator, transmission, and brakes go

Have you ever changed the fuel filter? A stopped up fule fillter will cause this.

matt

Thats why I am trying to get it fixed! My Bro said I should just open the dash and pull the check engine light. Good thing who ever buys it is buying it from me and not them!

I am changing the fuel filter tomorrow once I have enough time...Praying it is that because I don't want to buy a fuel pump!

Mrs. Hag has an '03 pickup. Speedometer quit a few months ago, then check engine light came on with 4 codes. Then water pump started leaking. Spent bunches on fixin the speedometer and a new fuel pump and was told the intake was leaking. Was told intake doesn't have a gasket. I used to do all my machanic work, but after talkin to friends that know. I spent another $200 to have that fixed. Good thing is water pump has stopped leaking for now. Truck is running way better and check engine light hasn't been on for 2 days. YEAH!!!!! Told Mrs. Hag----Merry Christmas for us both. She said ok. She LOVES her truck.

So did you change the filter... is problem still there?

When vehicles get old you gotta be ready for them to break, but if you take care of them they will last a long long time.

Yes I changed the filter today, the light went off for several days after I cleaned the MAF sensor so I thought it may have fixed it. Waited it out and it came back on after about 150 miles so I changed the fuel filter today. Hopefully that did it. I still smell like gas LOL

The filter was difficult to blow through btw, seemed like it was pretty gunked up because I had to blow hard through it to get the gas pushed through it and even still it was not easy to blow through like the new one.

Yeah I bet that was your problem, most folks dont change them like they should. I think that is also a large part of why people had so much trouble with GM fuel pumps was over working the pump pushing fuel through a blocked filter. I maintianed 3 chevy vehicle that were all among the problemed fule pump that all got over 200K on them before they were sold or traded and never had a fule pump go out.

Well the light came back on this time it was only bank 2 not both, the guy at auto zone said it is likely an o2 sensor. Not sure what to do now.

At this point you can replace it and hope.

I'd still bet on an intake leak and the problem coming back in the future.

GM Document 1899786 aka TSB PIP 3232B covers this problem.

where do I find that?

My 99 did the same thing when It got cold, but went away. I did change the spark plugs and never had a problem until it got cold. It never effected fuel mileage or power.

Just got it back from the shop, they said intake manifold and gaskets need to be replaced. There is a leak/hole between the manifold and gaskets. Got a buddy whose brother is a mechanic and is going to set me up. Thanks for the help guys