hesitation / bog down

[Brett Dikeman]

On Fri, Dec 11, 2009 at 1:41 PM, hayes myers <hayesmyers at gmail.com> wrote:

>  let off and revs fall off like it's going to die.

Classic signs of bypass valve failure, at least on the 20v's; the dead
giveaway is when the report is of the engine idle dipping or engine
dying coming off a freeway exit ramp.  It's almost always the cause
for that exact symptom.  Don't the late 10v MC2s have bypass valves
too?

If you've got a mityvac, disconnect the control line from the intake
manifold and apply vacuum.  The problem can be either the control line
cracking, or the valve diaphragm tearing.  It's a $50-ish part, so
definitely test before you replace.

If the valve is fine (or you don't have one)- maybe check that the
metering plate moves smoothly?

Oh, also, is the ISV clean and working smoothly?  If it's gummed up,
it can stick in a position where it is almost completely closed.

Brett