Prelude stalling problem (picture and movie included !) - need help locating some engine components

I've had a stalling problem for the past year on my '93 Prelude Si
VTEC.
It idles rough and sometimes stalls when warm and the revs drop
(typically when stopping for traffic lights).
The distributor recently failed and I was gutted that a replacement
didn't help me with the stalling problem.

So, from searching the web I reckon it might be the Idle Air Control
(IAC) valve (aka EACV Electronic Air Control Valve).

Can someone please tell me from this photo where this component is
located?
http://63.218.54.74/prelude/airvalves.jpg (200KB)

I've placed a red X where I think it is located.
Also, where is the fast idle control valve ?

While we're at it, is the EGR valve where I've marked EGR??? ?
And, finally what is the black think where I've written "What is this
?"


In case anyone is interested in helping me further, this link points
to a
movie of the rough idle.

http://63.218.54.74/prelude/roughidle.mpg (2MB)

I increase the revs 3 times
1. Initially the fan is on so it's quite noisy (ignore this one).
2. Fan stops and noise level drops. I pull throttle chord again,
engine runs ok.
3. I pull throttle chord the third time, idle drops very low and
engine almost stalls, then revs pick up to normal again. When on the
road it sometimes actually stalls (a few times a week). There is also
a rattle, this is coming from a vibrating heat sheild.


Notes:
There is one ECU code (code 12 - EGR lift valve). Local dealer has
checked vacuum and thinks it might be a bad ECU or bad wiring but
hasn't been able to find out for sure.
Local dealer hasn't been able to successfully diagnose the stalling
problem and after 2 visits has sent me home with a new battery and
distributor (which had failed).

 

On 24 Jun 2004 10:31:05 -0700,
(Chris) wrote:

Have you tried monitoring your fuel pressure?

 

1990 Prelude EACV:
http://www.honda.co.uk/owner/PreludeManual/62sf100/6-176.pdf

1990 Prelude EGR valve:
http://www.honda.co.uk/owner/PreludeManual/62sf100/6-209.pdf

1993 Prelude SiVtec EGR valve:
http://tinyurl.com/2nznl (Majestic online parts site drawing. Item 1 is the EGR
vacuum control valve. Item 3 is the EGR control solenoid valve.

Also, try some of the other Honda drawings accessible via the online manual
pages at

http://www.honda.co.uk/owner/workshopmanuals2.html

and

http://tinyurl.com/2ao3g

I think your X on your photo for the EGR valve is correct. Looks like my 1991
Civic's.

I do not think your photo shows the EAC valve next to the "what is this." The
drawings I have indicate something cylindrical but turned on its side.

snip

Updates welcome. Good luck.

 

Have you tried monitoring your fuel pressure?

It runs fine when driving, I figured any fuel system problems would be
noticable when driving, is that right ?

It is only on warm idle it is a problem (escpecially when dropping
down to idle).

 

Clean your throttle body. Better yet, take it apart from the car and clean
it thoroughly. My idle went from rough
to great.

Also, could be your main relay acting up.

 

Fuel pressure might be chronically or just intermittently too high or
too low if the pressure regulator has problems. Also there's a little
plastic filter at the fuel pump intake. This isn't intended to filter
out small particles, just big rust flakes and suchlike from the gas
tank. Sometimes big flakes lie against it and intermittently block
flow when flow rates are high, then fall back like little valves and
allow fuel to flow when flow rates are low.

Or, as you have guessed, the IAC valve may have the hiccups.
If you're going to do your own diagnosis, it's best to buy a shop
manual.

 

Great news! I got the exhaust centre section replaced (coroded) and
while I was there I asked the garage to replace the main fuel relay
because I also had an intermittent restart problem (once in a while
after stopping the engine to pop into a shop it wouldn't restart for
about a minute).
Now my rough idle, intermittent stall and intermittent restart problems
are all gone ! Dont know if it was the exhaust or main relay that fixed
it. Hope this helps someone else out !

 

sounds like the main relay, yes?