92 F-150 rough idle, dies when put into reverse

Did you remove and clean the IAC. They sometimes need to be removed and soak the valve poriton in solvent overnite to break some of the gum loose. You may also want to re-clean the throttle body using an old toothbrush to work all the gum lose aroung the throttle valve. Another thing you should check is fuel pressure. That vintage had an ovvasional pressure regulator failure for which they were recalled. If you pull the vacuum line from it and find fuel, it is definitely bad. Another indication is burning eyes when you are close to the exhaust. This usually results in poor fuel mileage. Another problem with that one is the tendency for the gasket between the upper and lower intake to leak. It is easily replaced but, you must torque it properly as they are very sensitive to this. A leak along this gasket can sometimes be found by spraying carb cleaner or a similar material along the gasket while looking and watching for a chenge in idle. I do not suggest ether as you can light yourself up easily and then it won't much matter how the engine idles. It can also damage the engine if you have a large leak and therefore get a larger slug sucked in. Unfortunately, the leak is usually on the right side where it is hard to ID. If you decide to replace that gasket, there are a couple of gotchas. Someone here can fill you in if you tackle it.

Lugnut

Thanks for the info Lugnit! I went out and looked at the engine, didn't (or missed it) see the IAC on it anywhere. SO I went to the Haynes manual and found no reference to the IAC. I did find a couple of good pics of the unit, so I know where to look and what it looks like, just don't see it. I am off to the store for another can of T body cleaner and will do that first with a nice new tooth brush! I will also pull a vac line and inspect, plus check fuel pressure. Mike

Idle Air Control (IAC) will likely be the problem. I think I paid about $50 for mine. They may be cleaned if you want to try that first.

Gary