My 302 runs great at speed. But does not idle. I was told it was rebuilt 6000 miles ago. I had the bad idle a couple of times driving it home. But mostly it ran great. It has gotten steadly worse. Now it will not idle at all. I have to turn up the idle screw to about 1500 to get it to idle, then it still dies when I put it in gear. I have looked for vacuum leaks and the only thing I foung is a bad vacuum advance canister. It has a HEI distributor. The machinist at the local speedshop said probably too much cam "fords do not like big cams". I think if it was cam it would not have driven well and then go bad. What am I missing. Any help would be appreciated.

 

Sounds like a vacuum issue. The first thing to do is put a vacuum gauge on and see what it's doing. Does it still have an egr valve? It could hang open and cause the same symptoms.

 

If it was too much cam it would have never run well. I agree vacuum is suspect. Is it fuel injected? Many other options if it is.

 

I found a bad vacuum advance diaphram. I replaced it and tried to set the timing. The vacuum advance was hitting on the manifold not allowing me to get the timing where it needed to be. I rotated the plug wires one spot to get more room to put timing in. Now it's hitting the fuel line. I had to reroute the fuel line to the back of the distributor. Was able to get the timing better. I need to find TDC and remark the harmonic balancer. Right now it's showing about 30 degrees BTDC. Right now it will idle but still dies when I put it in gear. Its coming along. Thanks for your help.

 

The distributor is probably in a cog or two off. Moving the plug wires is not the right way to solve that. Pulling the distributor and clocking it right is the correct method. The vacuum advance should point pretty much straight forward when the distributor is correctly installed.
Why would you start jacking with the timing if it was running ok? Timing doesn't change unless you found the distributor hold down sloppy loose. A bad vacuum advance wouldn't make it idle bad either, it does not affect timing at idle. How did you determine it was bad?

 

check the base plate gaskets on the carb for vacuum leaks.
it's possible carb is slowly working loose and eng. is getting more air than it needs
leading to a lean condition, check the sp. plugs for color that may indicate this.
Another thing that i once had an issue with was on the 170 in my econoline that it wouldn't idle worth a damn was that someone put the bottom timing sprocket on inside out (this was actually an engine shop with an excellent reputation)and only about a 1/4 inch of the key was contacting the keyway, so as the sprocket worked looser and looser over time the idle continued to get worse, after 15 years and about 30,000 miles and with a full load of stuff to run an event on the truck, in a hurry & heading to the event it finally sheared off leaving me on the side of the road. Up to this point
I messed with this engine, everything under the sun and in the book trynna get it to idle properly up to this point. so when i finally did fail it was a blessing in disguise in that it ended up solving a obscure issue that i would have never likely figgured out otherwise.

Mikie
near ottawa canada
58 m-100 panel & 64 econoline p/u

 

[QUOTE=willowbilly3;16527619]The distributor is probably in a cog or two off. Moving the plug wires is not the right way to solve that. Pulling the distributor and clocking it right is the correct method.
It is a HEI distributor. when I pulled the distributor out the gear stayed in the engine, common for a HEI, so I took the easy way out.

Why would you start jacking with the timing if it was running ok?
It was not.

Timing doesn't change unless you found the distributor hold down sloppy loose. A bad vacuum advance wouldn't make it idle bad either, it does not affect timing at idle.
It does if the timing is set to run without vacuum advance.

How did you determine it was bad?
I put a vacuum gauge on it.

 

You indicated the it was running ok then started misbehaving, which is not indicative of a timing issue unless the hold down was loose and the distributor could move on it's own.
If the timing was advanced enough to make it run ok without the vacuum advance, I'd think it would have exhibited some balky cranking since it would have needed 20 degrees or more of initial advance to run halfway decent.

Anyway, it sounds like you were on track with changing the advance, it's just that it's a lot easier for other people to give good advice if you don't leave big gaps in the steps you took in diagnosing and attempting a repair.

There's no way we can know your capabilitys unless you clearly describe the steps you have taken and the reasons you took them. As is often the case, it sounds like you are trying to straighten out a mess someone else left, much harder than just diagnosing a healthy engine gone sour.

I know they are expensive but I would be lost without my dial-back timing light for this sort of thing.