I seem to have fixed my code: P0171 P0174 issue...I guess

[adrianb]

Hey gang – wanted to share my experience working through the P0171 and P0174 (too lean bank 1 and too lean bank 2) codes.

2003 Tahoe LT 5.3 flex fuel engine, 79,700, bone stock.

Background:

I was tinkering with the truck a few weeks ago trying to see if I could eek out any more MPGs and generally improve it’s health short of a tune up and well, I fixed it until it broke.

I started by adding half a bottle of Seafoam straight to the crankcase, and a few dosages of Lucas at fill-ups.

Couple weeks go by and I get the codes.

Clean the MAF and throttle body. Reset codes, they came back

Couldn’t find any vacuum leaks. Reset the codes they came back

Decide to change the oil ahead of service indicator. Used to a Penzoil synthetic. Reset the codes and….they stayed off.

This makes no sense so I continue with my campaign.

Last Wednesday, I cleaned the MAF again and change the PCV valve, have the fuel filter changed….still no codes.

I put probably 350 miles on the truck since Thursday and am still code free.

I can’t think of how it makes sense but it seems like everything got better after the oil change. Coincidence?

I hope this helps somebody else.

Tags for future searchers: P0171 P0174 too lean bank 1 too lean bank 2

 

[sumo]

i hope it stays off too

 

[bkboatnsleds]

I would have guessed intake gaskets..

 

[adrianb]

I would have guessed intake gaskets..

that was pretty much the next thing on my to-do list

 

[91RS]

You need intake gaskets. Easy and cheap to replace.

 

[Merc1973]

Figured I would bump this instead of cluttering and starting a new one.

I too have these problems with these 2 codes just after a long trip from MD to MI and back in the cold blast of winter. I experienced them after I got back and went through the enclosed touchless car wash. There was a lot of vapor/steam in the air since it was 10 degrees out, it began to idle pretty bad almost like it wanted to stall, I kept the RPMs up until the wash was finished. Idle was back to normal after being in the cold dry air.Its been starting just fine like it always does, even cold weather. Slight rough idle now since CEL came on. Comes back after clearing the codes.


I also noticed that when accelerating lightly when going above 2200-2400 RPM there is a slight hight pitched whistle just as it's about to change gears. It''s always done this. Sounds like the whistle in my 73 Cougar when I had a really bad carburetor gasket leak.


Suggestions? Intake gasket?


I will clean my MAF and try some carb cleaner around the intake gasket....

 

[Scottydoggs]

for the love of god, never put seafoam in the oil crank case. known to kill a engine or so. intake and gas tank only for that stuff.

 

[HiHoeSilver]

for the love of god, never put seafoam in the oil crank case. known to kill a engine or so. intake and gas tank only for that stuff.

I agree with this. I will, however put some Kreen in there every once in a while about 1000 miles before a change.

 

[Doubeleive]

you couldn't pay me to use seafoam, I guess it works for some people though

 

[swathdiver]

Mobil One always in mine and they look spotless inside.

 

[shreksbrother]

Figured I would bump this instead of cluttering and starting a new one.

I too have these problems with these 2 codes just after a long trip from MD to MI and back in the cold blast of winter. I experienced them after I got back and went through the enclosed touchless car wash. There was a lot of vapor/steam in the air since it was 10 degrees out, it began to idle pretty bad almost like it wanted to stall, I kept the RPMs up until the wash was finished. Idle was back to normal after being in the cold dry air.Its been starting just fine like it always does, even cold weather. Slight rough idle now since CEL came on. Comes back after clearing the codes.


I also noticed that when accelerating lightly when going above 2200-2400 RPM there is a slight hight pitched whistle just as it's about to change gears. It''s always done this. Sounds like the whistle in my 73 Cougar when I had a really bad carburetor gasket leak.


Suggestions? Intake gasket?


I will clean my MAF and try some carb cleaner around the intake gasket....

I'm interested in this whistle you mention... I have a sound that sounds more to me like an alternator squeal... Only around 2-2300 rpm under light acceleration.

I too have those engine codes since it's been very cold.

I assumed my squeal was an alternator or something, and have been waiting for it to get worse for a year, but it never has. I never considered the intake manifold gasket being a possible issue.

I may order the parts to change that out in the next week or two. For sure to resolve that code issue, but possibly to eliminate the squealing sound.



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[HACK BLOCK]

I have this same code now and after a smoke test a shop determined my injectors are leaking

 

[HACK BLOCK]

I have this same code now and after a smoke test a shop determined my injectors are leaking

quick update... seems I fixed my p0171 and p0174 when I changed my evap purge valve