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John, ASE Master Technician
Category: Chevy
Satisfied Customers: 608
Experience:  ASE Certified Master Technician, ASE Certified Service Consultant, 22 years professional experience
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Where is the Mass Air Flow Sensor on a 2003 chevy

Customer Question

where is the Mass Air Flow Sensor on a 2003 chevy trailblazer?
JA: Does the engine stall right after starting? And what about hesitation or jerking during acceleration?
Customer: It shuts off right after starting. When it was running, there was not hesitation or jerking.
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I would like to fix it myself. I replaced the fuel filter so far. The fuel pump is working. You can hear it when you turn the key, just before starting.
JA: Anything else you think the mechanic should know?
Customer: I replaced the fuel filter. I know the fuel pump is working because you can hear it when you turn the key before starting
Submitted: 1 month ago.
Category: Chevy
Expert:  John replied 1 month ago.

Hello, my name is John.

The Mass Air Flow Sensor is in the 'accordian' looking tube that runs from the air filter housing to the engine. It is near the end closest to the air filter housing. 5 wires come out of the side of the sensor.

This description is for a 4.2 liter engine, let me know if you have a 5.3. Basically the same but just want to make sure I am looking at the correct engine.

Customer: replied 1 month ago.
Ok. I just checked. There is only one sensor on the accordion tube and it has two wires and is on the other end. There is no sensor on the end closest to the air filter. I looked in the tube and there does not appear to be anything in it.
Customer: replied 1 month ago.
here is the problem. Vehicle was running fine. Two days ago I started up the truck and it stalled. I tried again and it started right up. I had no issues the rest of the day or yesterday morning. At noon yesterday, I tried to start it again and it starts, but then immediately shuts off. It rumbles and if i step on the gas, it stalls faster. I replaced the fuel filter and the fuel pump is working because I can hear it when I turn the key before I actually start the car. Any ideas?
Expert:  John replied 1 month ago.

Still could be fuel pump. I have seen GM fuel pumps fail in every way possible including fuel pressure just a few pounds low causing problems like this. I would check fuel pressure with a gauge and see what is is exactly. If you give me the engine size I will give you the pressure spec.

Customer: replied 1 month ago.
It is a 4.2 ltr V6
Expert:  John replied 1 month ago.

Fuel pressure spec is 48-54psi. If you check it when you turn the key on it should be at the higher end of that (engine running would drop the pressure a little).

Expert:  John replied 1 month ago.

Just following up to see what you found out. If you have found the information I have provided to be helpful, please provide a positive rating for my answer.

Thank you