my truck dies right after startup, but after it runs awhile it's fine just when it's cold, however it doesn't idle real smoothly. I've been reading on here about the Iac causing rough idle, I couldn't find it on the I-6, There's a map to things like the map sensor, egr, etc. on the underside of the hood but the Iac is not on there (does that mean this motor doesn't have one?) I've cleaned the map sensor with electrical cleaner, blocked off the egr (with gasket material) put new plugs, fuel filter and air filter on it. My mechanic says it's probably the egr that's why I blocked it off, but that was not the problem. he checked the vacum lines and said they looked alright, I'm leaning toward the Iac (if there is one), cap or rotor, o2 sensor(even though the check engine is not on) plug wires (I did test them and they were all working, but my dads tester doesn't read the amperage or whatever going thru them).... sorry so long, I hope you guys can help me out I'm at my wits end... also it gets horrible mpg, like 14 on the highway, i would think a v6 would do better than that?????


more info.

93 f150 4x4
300 i-6
5 spd
3:55 gears

 

First of all, before you do anything, replace the spark plugs, wires cap, rotor, and fuel filter 7 air filter if they have not been replaced recently. This can cause idle and fuel problems, so just do it all.

The IAC has a 2 wire plug and is on top of the double throttle body where the intake tubes enter the intake manifold. This is simply a device that controls how much air enters the engine when the throttle body is closed (idle speed & start up). Remove your intake tubes and you can see how the TB works by manually pulling the throttle cable. The IAC on the top has a motor that opens or closes a valve to regulate how much air bypases the throttle body plates so that when they are closed a small amount of air still enters the intake manifold. The amount of air that it lets past controls idle speed. It is not a sensor, but rather a device that is controlled by the computer dependent upon other sensors input. It is possible for it to not be working and causing startup and idling problems due to insufficient air allowed to pass through it. If it is idling at normal RPM's I wouldnt think the IAC would cause dieing at idle or rough idle, not by itself at least.

I would start with the plugs and wires etc as no matter what they should be kept in good order. I never got better than 13 with my sixer 4x4, but i have a heavy foot. Ive heard of guys claiming 17-18 on the hwy, but never got anywhere close with mine.

Sorry if Im rambling, its 3:00 am.