My 98 F150 5.4L is having problems.

When I start my engine it idels fine for about 30sec-1min. After that it wants to die and it shakes pretty good. It also drops RPM's.

I am thinking its a vaccum hose but not sure. What are the possibe causes of this... what hoses etc..

Please help ASAP, I need to get this fixed.

Thanks Jake

The noise seems to be coming from the top of the motor towards the intake manifold.

We installed the AF-1 today as well but it started doing this, this morning before we installed the AF-1.

 

Sounds like the IAC [idle air controller]. Do a search here for pictures, location, and cleaning instructions.

 

Clean your MAF too, you would be surprised how much that effects idle..

 

I will try to clean them up. Were on the motor is the IAC located?

Also there seems to be a hissing sound.

 

On the back of the throttle body, theres three in this pic -





Hissing, that's is prolly coming from the PCV line behind the throttle body, the top line close to the firewall in this pic - they leak at the 90 degree bend -

 

We fixed the problem. My bro took it into a shop and the guy did something that I thought was pretty cool.

He started the engine, then he took a spray bottle full of water and sprayed it on the engine. Will all the mist floating in the air he could see were it was being sucked in at. He found the hose witch had a half inch cut/crack in it. He fixed it for free and off we went.

Thanks again for the help!

Jake

 

What hose was it?