In article <19933-43EA236F-26@storefull-3115.bay.webtv.net>,
bobbyswift@webtv.net (bobby swift) wrote:
> It does have a square plastic vacuum canister next to the battery on the
> passenger side,it has 2 lines that 1 runs to the carb.and the other one
> runs along the frame rail,I assume this one crosses over and goes to the
> fuel tank mounted on the drivers side.
That's the charcoal canister, has nothing to do with your problem.
Try looking at the underhood vacuum diagram, if there is a vacuum
reservoir, it should be shown there.
> This 300 6 cyl does have the
> electronic feedback carb.and that is new also.The engine does have a
> slight shake when it idles.I haven't found any vac. leaks yet.I've spent
> a lot of time trying to figure out why it keeps backfiring.
It's backfiring because either;
It's running extremely rich
The air pump isn't diverting on deceleration as it should
There is an air leak in the exhaust allowing air to be drawn into
the exhaust stream which gives the same effect as the air pump
not diverting.
Combinations of the above.
The air pump is controlled by two solenoids which are controlled
by the ECM. The solenoids control how vacuum is applied to
vacuum diaphrams on the air pump switching valves.
The solenoids are;
TAB (thermactor air bypass)
TAD (thermactor air divert)
The factory service manual has the proper procedure for
diagnosing the operation of these two devices.
> I was
> thinking about taking the whole exhaust off,rodding the converter.And
> putting a straight pipe or glass pack muffler on it.
I don't see any of this curing the backfire problem.
I -do- see the backfire getting you a ticket if that truck
backfires in front of a cop who's a bit on the jittery side...
> Any other
> suggestions are welcome.I would like to get it fixed.Thanks! Bobby
First thing is to assess whether the related systems are intact
and functioning properly, Ford used reject tomato juice cans for
vacuum reservoirs, 20 years is plenty of time for one to rust
out, they also liked to use hard plastic vacuum lines, 20 years
is plenty of time for them to get hard and brittle and crack.
You wouldn't believe how many supposedly unsolvable driveability
problems are caused by things as simple as this.
