Got these buggers a little while back. SES light has since gone off, come back on, then gone off again.

Here's the freeze frame data for the P0171:

ABSLT TPS 14.5
ENG SPEED 1495
CALC LOAD 15.7
MAF 3.5
MAP 19.5
COOLANT 194
ST FTRM1 2.3
LT FTRM1 19.5
ST FTRM2 2.3
LT FTRM2 16.4
VEH SPD 42
FUEL SYS 1 CLSD
FUEL SYS 2 CLSD

I was going through the diagnostic steps for P0171 and the value for long term fuel trim was 20. 19.5 is fairly close, but not above. In step 4 it lists what to physically and visually check if P0174 is also set. I have a fuel filter ready to go on, and I suppose I'm going to have to take an unlit torch around the vacuum lines and intake area to check for leaks. My concern is that perhaps the leak is internal and the intake manifold gasket is bad.

I know I'm headed in the right direction, just wanted to post and see if the more seasoned mechanics had any insight beyond what I've already stated.

Also, should I go ahead and clear the codes? The SES light is off but the codes are obviously still stored.

 

I would suspect a problem with the intake piping behind the MAF or possibly with the MAF itself. A leak in the LIM gasket wouldn't typically cause both B1 & B2 to go lean unless both sides failed at or near the same time.

 

Thank you. I have cleaned the MAF sensor itself within the last 6 months so it's possible that it was temporary and it's on its way out. I'll take a closer look in that area. So unmetered air entering after the MAF but before the TB could set the code? Or is it just any unmetered air after the MAF?

 

Any unmetered air after the MAF will trigger one or both of these codes. Where it enters will cause one, the other, or both. Typically if it's coming in between the MAF and the area of the throttle body, it will set both codes. Around the perimeter of the plenum seal or any one of the ports/sensors on the plenum, it would tend to set on one bank or the other unless it was a large leak.

 

There are to codes I need to know what they mean and where to locate them on the engine. p0171 and p0174. Can any one help? For a Chev 2000 Blazer 2 wheel drive.

 

How do you test a MAF meter?

 

This ended up being my forgetfulness to tighten the clamp between the MAF and the intake tubing after some work under the hood.

The quick test is if it's running poorly, unplug the MAF and if it runs better it would be wise to clean it. Make sure you use MAF specific cleaner and be EXTREMELY careful not to damage the actual sensor inside.

 

lol. glad you got it figured out. figure ill leave this here encase anyone searches these codes. i run across these alot in ford trucks and cars. and its pretty much always a vacuum leak, intake gasket, broken line, taurus's always have a pcv valve hose that goes bad. friend of mine just got this on his 2000 f150, havent went over there to mess with it yet