MAF Issue?

[Texas_WS6]

This is my sons stock 2000 SS Camaro.

I normaly tune my 2002 TA with GT-88 Turbo 408, and several friends forced induction cars.

Needless to say all of my tunning is with 2 Bar or 3 Bar Enhanced and with no MAF.

My son picked up this car and it needed some TLC. It ran a little ruff and used more fuel then it should. I threw my scanner on it to see what I could find.

I noticed the LTFT's and the STFT's go way way positive! I then replaced all plugs, wires, and fixed exhaust leak issues. Now the car is running good.

It still was sending the LTF's and the STFT's way positive as you can see on the log. I also noticed when first started the engine manifold pressure runs around 45kpa, and once it goes into Closed Loop and the fueling is finally corrected the manifold pressure drops to 35kpa or better.

It is obviouse to me the car is running very lean until the CL operation richens it back up.

I disconected the MAF sensor and made the MAF fault at 0. I reset the fuel trims and fired the car up. With the MAF deleted the engine manifold pressure at startup is very close to 35kpa. Once it goes into closed loop the LTFT's stay close to 0. The O2's start switching almost as soon as it goes into closed loop. Everything looks great.

I then purchased a new stock MAF sensor and put it on the car, flashed the stock tune back in and then made this log.

As you can see even with the new MAF sensor it is still starting very lean, and the LTFT's and the STFT's have to go very positive to richen the car back up.

What the heck is the issue here? Why is the MAF making the fueling so lean? The entire car is stock. I can not imagine I would need to work on the MAF mapping.

Is this normal for a MAF sensor and if so why? What am I missing here?

Any input would be great. Thanks

[flame]

check for vacuum leaks especialy along the intake gaskets

[mustangtuner77]

leaks for sure smoke test or take to someone who can!

[JamesLinder]

just go ahead and replace intake gaskets; does not take long and you will be certain that you have that problem eliminated. they will often cause an oil leak at the back
of the engine at the top where intake mounts to the block.

[flame]

The intake on an LS motor doesn't seal to the block. There is a seperate valley cover under there.