Intermittent idle/throttle problem

Hello,

This sounds exactly like a vacuum leak. I say this with extreme confidence because my car has a 4.6L engine in it which is essentially the same engine, yours just has a little bigger heads on it. When you have a vacuum leak the idle will "search" up and down at idle. The rich gas smell you are smelling is because the upstream O2 sensor is falsely reading a lean condition in the bank with the vacuum/intake leak and is trying to compensate for this by adding extra fuel to the bank.
A good way to check for an intake/vacuum leak is to get a propane torch. Crack it barely open so that propane is barely coming out. Make sure it is not lit. Start your vehicle and let it idle. Move the torch around the air intake duct, the throttle body, the intake manifold, all vacuum and Evaporitive Emissions (EVAP) lines. When the intake/vacuum leak is found, the engine will pick up as the propane is introduced into intake and burned into the combustion chambers. Please do this test and get back to us with what you find out.

Thanks,
Alex
2CarPros

Hello,

You can also do the same test with a spray bottle of water, just that the engine will bog down instead of rev up. I like the propane way because when I was going to school that is the way Honda of North America taught me to do it. I have included a link below for you to go to:

https://www.2carpros.com/articles/reduced-power-limp-mode

Please go through the guide and test for intake/vacuum leak and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros

Hello again,

No, a vacuum leak would not be intermittent. I have included for you a diagnostic troubleshooting guide for your vehicle's Electronic Throttle Control System in the diagrams down below. It will call for you to use a multimeter, so I have included a link below if you are unfamiliar with how to use one.

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go through the troubleshooting guide and get back to us with what you find out. This is probably going to take care of the whole ball of wax as well, because your original complaint would also be caused by this system malfunctioning.

Thanks,
Alex
2CarPros

The E and F-series in that generation in particular have a known issue with the TPS on the throttle body failing. There have been multiple updates to them over the years with the latest ones supposed to fix the problem. They are a bolt on replacement with the newest version being a box shaped part. When they start to get glitchy they can cause limp mode as well as running issues.
The miss with no code should be visible if you have a scan tool that can view mode 6 data in the generic OBDII mode. IE you just use the machine in generic mode, not using the vehicle specific mode. Fords are kind of quirky that way on many scan tools.