84 F350 4x4 460 auto.

Ok so I turn the key today and all it does is turn and turn and turn. After a few tries over about 20 min it ends up starting. Although not sounding good. In park/neutral it was making a hissing sound and idling rough with some engine shake. If I gave it some gas the motor sounded fine and didnt shake or sound like it was missing. When it came back down to idle it went back to hissing and shaking. I tried to put it in drive/reverse and the motor started violently shaking... Didn't think about trying to give it gas. This is all out of nowhere. The last work I had done was new battery, new terminal wiring and connections, and new solenoid. Sitting here waiting for a tow now...

What's you guess?

 

Vacuum leak from the brake booster?

 

I'd also be suspecting a huge vacuum leak, possibly a thumb-sized rubber plug someplace cracked apart and came off or something similar... brake booster could also do it...

 

Come to think about it my brake light came on while driving earlier today. What might I be going for at the shop? I'm not so handy (I'm learning).

 

Well, the light won't have anything to do with the brake booster, the light indicates a possible (probable) problem with the master cylinder BUT it could also be something as simple as the switch on the parking brake assembly... but, nevertheless, tell them you suspect a major vacuum leak at/in the brake booster but also tell them about the light - also tell them about its running characteristics of late. But let them fully diagnose it.... but it could be that a combo booster/master cylinder is in order.

Well, here is one thing you can do to test - pull the vacuum hose off the booster and plug it; then start the engine - does it run any better?

 

You guys nailed it. Large vacuum leak. She's all fixed up and running great.

 

Thanks for the update!