help please

Could even be spark or a vacuum line man, do yourself a favor and check the simple stuff first, if nothing pops time to test the fuel pressure.

Fuel pump, IAC could be your problem. Check the plugs/wires, IAC, normal stuff.

I agree with Winters, and I would start by cleaning the IAC. When it is running crappy, give the IAC a tap with the long handle screwdriver see what happens. It could be many things start with the simplest and cheapest, IAC, and hope you do not need a new fuel pump they are kind of a hassle to change.

I think you are on the right track, I agree its fuel related.

Check your gas cap...or was your cap replaced? Agreed, this is a fuel issue.

This is something I have recent experience with.

The Mustang's gas tank is vented via the charcoal canister to air all of the time. The air vent is behind the fuel filling area. The tank vent can be accessed from the left side of the car behind the wheel. The vent is the larger slip fit line. Disconnect and blow very low pressure air (< 1 PSI) down the line away from the cansister. It should blow easily.

For the Mustang, the gas cap can not cause this particular problem. But a clogged charcoal canister or canister vent perhaps could.

A valid test for a clogged gas tank vent would be to open the gas cap and see if there is any improvement. Obvisouly, if allowed to continue this will throw an EVAP related DTC.

If it were my car, the 1st test would be a fuel pressure test. I would use an ODB2 scanner to monitor the fuel pressure as reported by the PCM. In this way, you can also confirm if the fuel pressure vacuum reference line is connected and the PCM is seeing a reasonable fuel pressure from the sensor.

Note, this could also be trash or water in the gas tank clogging the fuel pick up sock.

wmburns said:

For the Mustang, the gas cap can not cause this particular problem.

Click to expand...

Ahh, but what if the cap had been swapped with an aftermarket cap? Some folks have done this with the high gas prices we are dealing with these days.

Runs rough after 10 minutes of running good? Could be something related to evaporative purge.

However, if it is charcoal canister purge related, you would expect it to improve after a few minutes when the evaporitive purge is complete.

Do you have an ODB2 scanner to read operational data?