Hi there, I own a 2004 F150 with the 5.4 V8, at 125,000 miles. I have a few questions some things going on.

Why would connecting the MAF Sensor stall the truck.

With the sensor unplugged I am getting a "Puffing Effect" out the tail pipe???

Thanks in advance for your thoughts.

 

Why would you disconnect it in the first place? The PCM needs the MAF to run correctly.

 

I was wondering this as well.

 

The MAF has to be connected. Plain and simple.

 

Clean or replace the MAF...

 

The garage that I was talking to thought it was the MAF. They said to disconnect it as it determines the fuel air ratio. I installed a new one and it is still puffing out the tail pipe. Now they think it needs a new motor. I don't think so....

 

I would find a new mechanic for sure.

 

Wow just wow. That garage needs a some education. O2 sensors send the signal to the PCM to determine a/f ratios. The MAF monitors the air coming in to add to the information the PCM needs to determine fuel.
Plugging the sensor in and stalling indicated a short or some other electrical problem. It's going to "puff" when it's unplugged because it has no way of monitoring intake temp/volume, thus causing a dangerously lean or rich ratio. Check the voltage to the MAF and see if it is getting the proper current to function, since the new MAF didn't help.

Have they even done a compression test to determine you "need" a new motor?