"Chopface" <thename_is_slick@yahoo.com> wrote
> 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 think I learned the somewhat-hard way that bleeding must be taken very
seriously, or air pockets and so inadequate cooling results around vital
components like the Idle Air Control valve (a.k.a. EACV).

I'd just add that it will likely take at least 40 minutes to get the
radiator fan to come on the first time (which the manual says to do when
bleeding) and so do a thorough, proper purge.

I did a bleed this summer, and the ambient temperature was 79 degrees F.
Forty minutes is about how long it took for the fan to kick on. One is
supposed to let it come on twice.

Remember that both www.autozone.com and the UK site
http://www.honda.co.uk/owner/workshopmanuals2.html
have detailed guides for your Honda. At the UK site for my 91 Civic (1.5
liter), I used the Concerto manual a lot. It's engine is the same or
identical to my Civic's.

I took off and disassembled my Civic's EACV this summer while
troubleshooting idle problems, but could have spared myself this trouble
had I first simply purged the cooling system of air.

> 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?