1986 5.0 L Engine surges at idle

Technically it could be a bunch of things, try checking out a quick series of articles on how to solve idle problems...

Sound like the IAC. (idle air control) Had the same thing on my 93 5.0. Cost about $60.00 + -.

JP

Gary, a little imore info if you please?

Engine lope or surge is difficult to track down so bear with me.

What type ignition are you using? IE: Coil, wires plugs? Are you using after market hi energy ignition such as accel, msd? Have you recently replaced TPS? O2 sensors, EGR sensor or EGR switch? Have you replaced your fuel flow regulator? Have you replaced fuel filter or fuel pump recently?

I'm going to take a guess that your ignition system is surging and sending to much voltage from the coil. Your coil maybe bad or when you had your ignition module replaced an after market system was used. Ford already uses high energy ignition in their 5.0 Liter engines so if you were told that an aftermarket high energy system would improve boost this would only be true if you increase boost by adding a turbo or supercharger to your configuration where additional enrgy is required.

JP, I went that route also and first cleaned the IAC and then replaced it but its the ignition that Gary replaced that leads me to believe its energy surge that is causing his engine lope.

I have replaced in the past the fuel pump & filter.

As far as the ignition module I just replaced with a stock module. The engine is completely stock. I have not replaced any sensors. I do have to replace the mufflers as one had a leak just before the muffler and both are starting to burn through juss after the mufflers.

Thanks for the help. Is ther any way to test the IAC before investing $ 60

Thanks,

Gary