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A. Penland
A. Penland, Ford Senior Master Technician, ASE
Category: Ford
Satisfied Customers: 6212
Experience:  ASE Master Certified, ASE Advanced Gasoline Engine Performance
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My name is ricky. I have 26yrs experience, I am working on a

Customer Question

Hi my name is ***** ***** have 26yrs experience, I am working on a 2003 ford Taurus with a 3.0 ohv engine. The problem I am having is the engine dies out when the a/c is turned on at idle, or when stopping . The engine runs good while cruising. The engine will start right back. I replaced the egr valve, tps sensor, cleaned the throttle body, and I replaced idle air valve. I sprayed brake cleaner around intake manifold and can not find vaccum leak. I have a trouble code of po456. Can you help?
Submitted: 10 months ago.
Category: Ford
Expert:  A. Penland replied 10 months ago.

P0456 - EVAP Control System Leak Detected (Very Small Leak)

This code is for a small leak the PCM (Engine Computer) has detected in the fuel vapor system between the fuel tank and the engine. Not a vacuum leak.

I just need to know if the AC has to be on when it stalls when stopping?

Customer: replied 10 months ago.

The engine stalls with a/c on or off when stopping.

Expert:  A. Penland replied 10 months ago.

Make sure all the hoses are connected to the air intake box and tube. Make sure the air filter box is properly and completely closed.

Customer: replied 10 months ago.

All air ducts and hoses are connected

Expert:  A. Penland replied 10 months ago.

Does the tool you used to get the trouble code also monitor the sensors from the PCM (Engine Computer)?

Customer: replied 10 months ago.

Yes, I am using a snapon midos

Expert:  A. Penland replied 10 months ago.

See if you can monitor the Long fuel trims and the short fuel trims for the engine while it is running.

Customer: replied 10 months ago.

  • LFT bank 1 idle 5 to7

  • LFT bank 2 idle 9 to 11

  • LFT bank 1 2000rpm 4 to 5

  • LFT bank 2 2000rpm 10 to 12

  • SFT bank 1 idle 0 to -1

  • SFT bank 2 idle -1 to 2

  • SFT bank 1 2000rpm -2 to 3

  • SFT bank 2 2000rpm -3 to 2

  • fuel pressure 40 psi

Expert:  A. Penland replied 10 months ago.

Ok, unplug the VMV (Vapor Management Valve) electrical connector and drive the vehicle and see if the stalling problem is still present. We have seen the VMV stick open and flood the engine with fuel vapors from the fuel tank.

Customer: replied 10 months ago.

I unplugged electrical connector at valve. I also plugged off the small vaccum line to valve and I plugged off nipple on plenum where the large line connects.. The engine still stalls.

Expert:  A. Penland replied 10 months ago.

Ok. With the scan tool attached watching the SHRTFT for both banks. Start the engine and slowly spray carb cleaner or brake cleaner around the intake manifold and see if the fuel trims change.

Customer: replied 9 months ago.

There is no change in fuel trim.

Expert:  A. Penland replied 9 months ago.

Have you actually tested the actual fuel pressure with a manual fuel pressure gauge connected to the vehicle?

Customer: replied 9 months ago.

I checked fuel pressure it is 30 to 40 psi. 30 at idle and go to 40 when accelerated

Expert:  A. Penland replied 9 months ago.

Disconnect the line from the VMV from the manifold and watch the fuel trim. If the valve is sticking open, the vacuum line disconnected will not effect the operation of the valve and it will still allow fuel vapors into the engine.