Still having problems with codes 171 and 174!

[woodsboy00]

Truck still shows right and left banks are lean. Truck will sometimes (normally cold) idle between 1000-1400. Other times (normally warm) it will idle normally around 650-800 and then drop suddenly to 350-400. Other times it will idle as if nothing is wrong at all. I think it has to be and intake leak, expanding and contracting with the heat. Anyway to test this?

[farmtruc]

Ya, sure is.
Find a shop with a smoke machine and smoke that engine. Easiest and most effective way to determine where the leak is.

[woodsboy00]

Well, I'm a broke college kid. Can't really afford to take in to a shop! I am pretty mechanical, got a buddy that is a mechanic to help me also. I have heard you can use propane or carb cleaner to find a leak. If you can, I will probably just do that. I'm hoping its an intake gasket leak, cause surely that can't be too hard to do

[96/chevy/pu]

thats how we did it in the old days before smoke machines. Much safer with smoke machine though.

[bootlife]

Soapy water and a spray bottle, carb and choke cleaner works to. spray 1 side at a time and listen for the motor to run better for a few sec. if ur using the soapy water listen for the motor and alot of times you will see bubbles.

[AFSP1211]

What year truck? Return style fuel system? Check fuel pressure regulator (if eqpt)? Does it bog under throttle?

[woodsboy00]

Well, Saturday night me and my buddy used carb cleaner, and it seemed to bog instead of idle higher? The more we would spray in that spot the harder it would bog. Seems like a leak to me! Should I go ahead and replace it? And Summit has them for $40 vs in town O Reillys for $80! The summit ones were fel-pro I think. Any particular brand to buy OR to stay away from?

[woodsboy00]

And the truck is a '03 with the 4.8. Doesn't bog under throttle at all. . . Just idles bad sometimes, and other times runs like a champ.

[farmtruc]

if you use OEM dealer gaskets, they always do the job.

[woodsboy00]

Thanks for the help guys! Gonna tackle this pretty quickly. Saturday morning hopefully.