I have an 89 F150, 5.0, C6, 4x4. The problem I have noticed is that when the brakes are applied and truck comes to a stop, there is a mis or studder in the engine. Like you get when you have a bad plug, but not all the time. It doesnt do this everytime. Im thinking vac leak somewhere. If I let the truck idle down the road there is no studder. Only when I hold the brakes at a stop do I notice it. Any ideas?

 

sounds like a vacuum leak. does your pedal go all the way to the floor. since the engine creates the vacuum for the vacuum booster and when one presses the brake pedal they are allowing air into one side of the booster and creating pressure on the other, so if you had a bad seal in the booster the engine would not be creating enough vacuum. thus causing the miss while at idle while the brakes are pressed.

i hope that made some sense its real late so if i am completely off my rocker somebody please correct me.

 

Yeah it makes sense. No, the brakes work great! Just noticed today that when I go to take off after having had the brakes held. It does misfire a bit until you get going. Its not much, just annoying. Might change wires, plugs, cap and rotor.

 

can you pull codes

 

I can take it to a parts store and they will for free

 

Parts stores can't pull your codes because they're retarded. They scan OBDII and yours is OBDI. Sticky at the top of the page explains how to pull codes. I'd also check the fuel pressure.

 

Im still leaning towards a vac leak. It doesnt do it in park at idle. Only in gear at idle.

 

Tune-up...

 

Yeah I am doing a tune up for sure.