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Brad
Brad, ASE Certified Technician
Category: Chevy
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Experience:  ASE Certified Master Technician
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Im getting a PO172 and PO175 too Rich Bank 1 and 2.

Customer Question

I'm getting a PO172 and PO175 too Rich Bank 1 and 2. What is likely the problem?
Submitted: 6 years ago.
Category: Chevy
Expert:  Brad replied 6 years ago.
Hello Taylor, and welcome to JustAnswer.com!

If the vehicle seems to drive OK, and the only symptom is the presence of these codes, check the Mass Air Flow sensor, as it may be installed backwards!

graphic

This sensor is mounted at the air intake hose, near the air filter box (per the illustration). There should be an arrow stamped on top of it to indicate air flow direction (make sure the arrow is pointing away from the air filter).

Good luck!
Brad, ASE Certified Technician
Category: Chevy
Satisfied Customers: 2365
Experience: ASE Certified Master Technician
Brad and 15 other Chevy Specialists are ready to help you
Customer: replied 6 years ago.
Reply to Brad's Post: The Mass Air Flow sensor is installed in the correct direction. The vehicle started running rough when the check engine light came on.
Expert:  Brad replied 6 years ago.
Darn! I thought for sure that would be your problem, as this causes this code 95% of the time.

A bank1/bank2 rich condition is actually very uncommon, as you usually have to have a pretty sever fuel system problem to cause this. Assuming the ignition system is in good shape (plugs not fouled out and all), the next likely possibility is a leaking fuel pressure regulator.

This uses vacuum to regulate fuel flow through the fuel rail, and sometimes the diaphragm inside this unit can fail, allowing that fuel to bleed right through the part into the vacuum system in the engine, causing too much fuel.

To check or replace this part, you have to remove the upper intake assembly, remove the 'spider tubes'.. the tubes that supply fuel to each cylinder, and then you can access the regulator, mounted inside of the upper intake. The fuel regulator looks like this:

graphic
Customer: replied 6 years ago.

Dang that sounds like a lot of work. Do you have a diagram of the upper intake assembly?

 

Customer: replied 6 years ago.

I'm going to go a head and accept but if you have a diagram of the upper intake assembly it would be greatly appreciated.

Thank you!

Expert:  Brad replied 6 years ago.
Here you go.. this should help. It looks a lot worse than it is:

graphic

REMOVAL

1. Disconnect the battery negative cable assembly from the battery negative terminal.
2. Remove the air cleaner assembly. Refer to Powertrain Management.
3. Remove the wiring harness connectors and the brackets and move aside.
4. Remove the throttle cable and the bracket from the upper intake manifold.
5. Remove the cruise control cable, (if equipped).
6. Remove the fuel lines from the intake to the rear of the block. Refer to Powertrain Management.
7. Remove the ignition coil and the bracket. Refer to Starting and Charging
8. Remove the upper intake manifold.

INSTALLATION

1. Install the upper intake manifold gasket.
2. Install the upper intake manifold. Use care not to pinch the injector lines between the upper and lower intake manifolds.
3. Install the upper intake manifold bolts. Note the marks made at disassembly for proper stud location. Install the two corner studs first in order to help align the two halves. ALLDATA Editor NOTE: Other than the two torque passes listed below, the OE Manufacturer did NOT address or supply a bolt tightening sequence for the upper Intake Manifold for this model year, or other model years where this 2 piece manifold setup is used. A "Play It Safe" final tightening sequence would be to tighten from the center most bolts to the outer most bolts.
4. Tighten the bolts in two steps:

1. Tighten the bolts on the first sequence to 5 Nm (44 inch lbs.) .
2. Tighten the bolts on the final sequence to 10 Nm (88 inch lbs.) .

5. Install the purge solenoid and bracket. Refer to Powertrain Management.
6. Install the ignition coil and bracket. Refer to Starting and Charging.
7. Install the PCV hose et the upper intake manifold.
8. Install the fuel lines from the intake at the rear of the block. Refer to Powertrain Management.
9. Install the cruise control cable (if equipped).
10. Install the throttle cable and bracket from the upper intake manifold. Refer to Powertrain Management.
11. Install the wiring harness connectors and brackets.
12. Install the air cleaner assembly. Refer to Powertrain Management.
13. Connect the battery negative cable assembly to the battery negative terminal.

o Tighten the bolt to 15 Nm (11 ft. lbs.) .
Customer: replied 6 years ago.
Thank you! Have a great day!

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