Vacuum Leak on my 86
 

I have a vacuum leak-so I'm told because my 86 has started ideling rough and the "EMISSIONS" light came on Sometimes it dies I checked hoses and they look good? any thoughts,tips/tricks in tracking them down
Thanks
Dusty

well on the efi motors there are alot of vacume hoses, if you can hear the whistle of a leaf your lucky. if you can hear it get a piece of hose hold it up to your ear and the other end around where you think the whistle is itll help find it. if you suspect its around the manifold, upper to lower probable. get soem cerb cleaner or throttle body cleaner with a straw and spray it all around the gasket if it sucks there the rpms will increase as its getting more fuel intake. as far as the emissions light im not sure what trigers that i thought it was just somethign on a timer that came on every so many miles. someone else here shoudl be able to tell you more about that. and maybe even how to turn it off. for as muck as a rough idle start with the basice. when was the last tune up plugs wires coil cap and rotor. if thats all recent try fuel injector cleaner, the stuff in teh gas tank isnt much but it can make a difference, the ideal thing is if you local mechanic can do a BG service or somethign which involves running some strong chemical right into the fuel rail thats guranteed to make a difference. a good throttle body cleaning and air cleaner is always a good thing too.

The Tune up in about 1 month old,plugs,wires,cap,rotor air filter fuel filter Vavoline 10w40 oil Fl1A filterThier is a cap looking thing on a "Bridge at the back of the motor between exaust manifolds.It broke off about 2 months ago and sounds like a diesel!What is that called?it happened WAY before the rough idel
Dusty
PS Where do I look next for the Vacuum leak or rough idel?Any common places

The thing that goes to both heads in the rear is part of the air injection system. There is a name for it but I'm drawing a blank.

As for the vacuum leak, Check the gasket between the upper and lower manifold. My F150 had a leak there, my Bronco had a leak there, my friends F250 had a leak there... notice a trend? It's pretty easy to do, but you need a special torx bit to get the bolt between the runners. I got mine from snapon but it was like $30. Maybe pepboys or sears has one. It's a 6 inch long bit (using a regular torx with a 6" extintion won't work. The torx part that comes out of the socket part is like 6 inches long). It can be done in about two hours (or less).

While your there, change the valve cover gaskets if they're leaking and you can change the crossover tube for the airpump too.

Ohh and the emissions light is on a timer, it's not an error light. I think a scan tool can turn it off. Search the forms for reseting a computer or resetting codes.

As for the rough idle. Try a power balance test. With the engine running and warm, pull one wire at a time and see what difference it makes. Use plyers and hook a ground wire up to them to keep from getting shocked. If there is one cylinder that doesn't change much then you've found your roughness. Swap the plug wire with another cylinder and see if the problem moves. If it does, then the wires bad. If not, swap a plug. If the cylinder still is rough then it's probably a bad injector.

If you can't find a bad cylindar then it still could be bad injectors, it could be a bad distributer or even a loose timing chain.

Hope this helps.