87 F150 Won’t Start

[RonD]

Start engine
Pull off vacuum lines, one at a time, and plug port with finger, especially brake booster line, for other symptom

If idle drops with a port blocked then the hose or device at the other end of that hose is leaking

 

[Mhfco6]

Start engine
Pull off vacuum lines, one at a time, and plug port with finger, especially brake booster line, for other symptom

If idle drops with a port blocked then the hose or device at the other end of that hose is leaking

The line going from the manifold tree to the firewall, looks like something for the cabin air. That’s the one that’s giving me trouble. Once tree was plugged it idled down but was running extremely rough. Saw some smoke and looked under the truck and the cats were about to catch fire, haha.

What is the vacuum device called that has failed?

Does anyone know the exhaust pipe size between the 2 cats? And what is the pipe size after the second cat? Looks to me like 2.5” and 2”. Can anyone confirm?

Also can anyone say that this timing mark sticker is correct?

 

[RonD]

The cab vents, defrost, panel floor, are "powered" by vacuum motors, vacuum holds them in selected place, defrost is default, no vacuum present

But that hose from firewall should run to a Vacuum Reservoir, a plastic or metal "can", that is also connected to vacuum manifold(tree) with a check valve in between
Check valve keeps vacuum level in reservoir the same to hold vents in the cab in place as vacuum in intake changes when accelerating

Some vehicles came with vacuum gauge on the dash, i.e. gauge that point at "green" for best MPG and "red" for bad MPG
This would need a direct vacuum hose

Hot Cats means Rich fuel mix or clogged exhaust

Don't know pipe size

 

[Mhfco6]

Just noticed this line disconnected on the plastic case (firewall) before the check valve, but did not help the high idle. The only way I can get the idle down is to disconnect the line I colored red and plug the tree. The idle is low this way but the engine idles really rough.

 

[Mhfco6]

So far so good, seems the IAC was sticking.. still is but not as bad.. reset timing and purring like a kitten.

 

[RonD]

"red" vacuum line is connected to the MAP sensor, computer uses this sensor along with throttle sensor, to set air/fuel mix based on engine load, called a Speed Density system
Important sensor
Its just mounted to the firewall doesn't go thru

Ford changed to a MAF sensor in later years, unfortunately you can't do that

You can read up on the older Ford systems here: http://www.fuelinjectedford.com/
Good page to bookmark