This issue has baffled me for over a month now and I am still no closer
to discovering what's causing it.
I have a 93 Ford Taurus GL with a problem with rough idling (to the
point of stalling if gas is not applied to keep it at a high enough
speed) and, of course, stalling. The problem has persisted after I've
changed the fuel pump and fuel filter, the EGR valve, the Idle Air
Control Valve and the spark plug cables. Code readouts point all over
the place, if the car generates codes at all. Codes, when they are
logged, point to a vacuum issue. The rough idle problem does not
always start first thing.
In the mornings, I can sometimes run the car halfway to work before it
misses a lick. Sometimes it can go all day and not miss a beat. And
then there are some days I don't get out of the driveway.
There is a whistle when the engine is idling in the driveway but, in
the location I hear the whistling, there are no vacuum hoses to be
seen. So, if there is a vacuum leak, I can't locate it. Not only
can't I locate it, it is beyond intermittent.
Performed a leak test around the intake manifold and there was no
leaking there. I have even cleaned the carbon from the butterfly valve
on the intake and it has not helped the problem any.
I'm nearing my wits end here and, if I take it into a mechanic, I'd
like to point to something more specific than 'it has an intermittent
problem, possibly related to the vacuum'. Any ideas or help that you
can offere would be most appreciated.