Hello,

I've got a '91 Civic Si with the stock 1.6L MPFI setup and a manual
tranny. I put an AEM cold air intake on in August and I don't suspect
any problems from it directly. It has 136k miles and is well maintained
as of late (IMHO).

Over the past few days the car has developed an idle problem. I have no
check engine light indication. The ambient air temp. has been around
30-40 deg. F lately. The fast idle seems normal when I start the car,
but after I have driven the car up to operating temp. (either cruising
on hwy. or around town) the idle bounces repeatedly from 750 - 1250 rpm
in neutral with the clutch out. I also seem to be getting lower gas
mileage (low 30's vs high 30's).

I changed my coolant this summer, and never bled the system. I just
squished my upper rad. hose a bunch after filling it up and running it.
I know that the dashpot diaphragm that keeps the throttle plate from
slamming shut sticks sometimes, but I don't think it would be the source
of my problems here.

I don't have my Helm manual currently and am going to work on my car
this holiday weekend. So far here is what I am going to try:

bleed cooling system
check all vaccum connections
check for leak around intake manifold and throttle body gaskets
check EACV

Does anyone have any other ideas?

Thanks for your time,

Mark