I have a 1996 Camaro Z-28 with the LT-1 Engine. I bought it with high miles (18x,xxx) and been slowly fixing each proublem. But im getting trouble codes P0171: Bank One and P0174: Bank Two. Both saying lean system. The car has a aftermarket intake, and a modified MAF sensor. The MAF on there doesnt have the mesh inside of it like the stock sensor has. I bought some additives to put in the fuel tank to clean the fuel lines and injectors, but i also suspect that the MAF i put on there has too much air flowing through, or a defective O2 sensor. Car seems to run fine, when in park the car's rpms bounce between 800-1000 rpms, while after drive and braking at a stop light etc.. the car idles at 600-700 rpms.

 

The codes set when the long term fuel corrections reach there upper limits.... they can't add any more fuel, in response to an O2 sensor signal that is telling them the engine is running lean. Since both sides are getting the code, its something that affects both sides, like:

-low fuel pressure
-low MAF sensor readings
-large vacuum leak
-faulty O2 sensors or wiring on BOTH sides
-exhaust leaks on BOTH sides, before the O2 sensors (would make it actually run rich - since its a "false" lean)
-misfires on BOTH sides (would make it actually run rich - since its a "false" lean)

Stock programming is a 650rpm idle in neutral, and 550rpm in drive. Stock tach typically reads 100-200rpm higher than actual. A variation of +/- 25rpm is normal. +/- 50 or 100rpm is excessive. May indicate the engine it getting air at idle from somewhere other than the idle air control circuit (vacuum leak).

 

More often than not when bank 1 and 2 set codes together it's your MAF that's giving you problems, like Injuneer suggested. And since yours is "modified" and descreened, I'd be willing to bet that's where your problem is.

 

I see i also noticed a broken vacuum hose so i purchase some and plan on yanking an replacing it soon when i have time and if its warm enough outside.

 

I small vacuum leak will not be enough to set codes for both sides expessialy. I would be looking at your maf as the culprit. Unplug it and see if the car runs better and those lean codes go away.

 

If it is the MAF should i tune the engine to compensate, or get my old one (which has the screen) back, and run it?