Honda Car Forum

My theory is that the coolant temp sensor is sending a low resistance to the
ECU. The ECU thinks it's hot (but actually cold engine) so it puts out non-rich
mixture. This is indicated by the erratic idling on a cold engine sitting
longer than 2 hours. To override this function just unplug this sensor
connector then crank the motor. Watch how it runs. (The intake temp, throttle
sensors, etc also plays a role in fuel mixture.)

Second theory. The cylinders or cylinder is/are experiencing a flood. This is
indicated by the erratic idling then clears up. To eliminate fuel or clear up
fuel, unplug main relay fuse (ECU or fuel pump) and crank for 10 seconds.
Rumors (in my tech class) suggests that pressing the gas pedal to the floor or
in certain ways will turn off injectors for the first few seconds of starting.
Worchid

Thanks for your theories.

> My theory is that the coolant temp sensor is sending a low resistance to
the
> ECU. The ECU thinks it's hot (but actually cold engine) so it puts out
non-rich
> mixture. This is indicated by the erratic idling on a cold engine sitting
> longer than 2 hours. To override this function just unplug this sensor
> connector then crank the motor. Watch how it runs. (The intake temp,
throttle
> sensors, etc also plays a role in fuel mixture.)

This could very easily be the problem. I think it could be that when engine
sits in
the sun engine isn't allowed to cool and computer thinks engine is hot when
infact
engine is cold. I'll trie this (but I'll connect the resistor on connector,
not just
disconnect it).
Bye the way, it isn't idling erraticly it idles perfectly when in a 1-2
seconds after
starting.

> Second theory. The cylinders or cylinder is/are experiencing a flood.
This is
> indicated by the erratic idling then clears up. To eliminate fuel or clear
up
> fuel, unplug main relay fuse (ECU or fuel pump) and crank for 10 seconds.
> Rumors (in my tech class) suggests that pressing the gas pedal to the
floor or
> in certain ways will turn off injectors for the first few seconds of
starting.

Can this theory explain why engine starts great when car hasn't been sitting
in the sun?

About idling it seems to me as if it is not enough fuel in first few cranks
in lines
(evaporated fuel in fuel lines) and when fuel gets to lines after a few
cranks
everything works great.

"Wdyorchid" <wdyorchid@aol.com> wrote in message
news:20030827094300.19823.00000004@mb-m28.aol.com...
> Theory 1: Fuel pressure regulator may not retain adequate pressure for
initial
> burst of 42 psi. You may be starting on 32 psi, for example pressure
increases
> as motor runs.
> Diagnosis: Pinch the return line with a piece of cloth & vise grip.

Can you explain why this would be problematic only when car has been sitting
in the hot weather (sun) and not in the morning?

> Theory 2: Fuel pump relief valve. This retains pressure after motors stops
for
> ease of starting, according to service manual. Pressure may drop if pump
does
> not run continuously.
> Diagnosis: Apply power to fuel pump directly to run fuel pump
continously.

Can you explain why this would be problematic only when car has been sitting
in the hot weather (sun) and not in the morning?

> Overall, to have a good clean start, the fuel mixture must be precisely
mixed
> by adequate pressure, precision spray nozzles combine with a cool
unrestricted
> airflow. Starting with four or five crank is an indication poor mixture
and/or
> pressure. I hypothesized that the 4-5 cranks is enough to dump enough fuel
into
> the chambers that's not supposed to be there. The only way to clear it up
is
> through erratic idling. Some cars, I own one just like yours, will not
start
> after six cranks.

Interesting thing is that when after cranking for few times it starts RPMs
are lower
then they should be (like 500) and then they in a 1-2 seconds increase to
1100-1300 (it is not cold out, in the morning it starts great and RPMs
immediately
jump to 1500) which I think is ok, and after another 1 second oil indicator
goes
off, and it is all working great after that.

BTW, I noticed that my distributor cap is cracked where screw is could that
be
any reason for poor starting.

Main relay is surely not the reason here because I tried another relay from
my
friends Civic and I experienced the same starting.

I think it is very important thing that it fails when sitting in hot sun it
is about
35 degrees C (95 degrees F). It starts ok when sitting in the shade, and it
starts ok in the morning. But when I have been driving it in the afternoon
and temperature outside has dropped in the evening (probably it hasn't
dropped much in degrees but no sun anymore) it still started poorely.

My theory is that fuel evaporizes in fuel lines and it needs a few cranks
for fuel to
reach the fuel rail, and everything goes ok when fuel reaches the rail.
What do you think about that?

> During my testing of four injectors (from my civic not related to
above)
> outside I'd notice the initial burst of fuel being sprayed is accompanied
by a
> drip or drooling effect. Then clears up as it progresses. This was an
already
> known phenomenon on Civics but not most Accords. This, however, did not
affect
> the car's starting ability but will be. It was replaced soon after
discovery.
> Worchid

I put 1.5k Ohm resistor instead of ECT (engine coolant temperature sensor)
and it started poorely so I guess that is not the problem.

"Ricky Spartacus" <RickySpartan@mailandnews.com> wrote in message
news:d1e1d73f.0308290252.4971ebf9@posting.google.c om...
> Mechanical theory 3: Low compression. Compression increases as oil
> comes in contact with cylinder walls. Until oil has reach wall at max,
> oil light will not turn off. Low compression could mean low idle rpm.
> Diagnose: Test compression or clean oil filter screen.

Does that explain why everything is fine when cold?

> Electrical theory 4: I suggest unplugging the TW coolant sensor

I tried this (I plugged 1.5k ohm it is a walue as if engine is not
completely
cold) I measured TW (Engine Coolant Temperature sensor ECT) (TW is
old name for what is now called ECT) and it is ok (300 ohms when engine
hot).

> or O2 sensors, the computer may go into limp mode bypassing any electronic
> problem in the computer.

I haven't tried O2 sensor.

> You must reset computer if it does not idle
> to spec by disconnecting bat (or other methods) for 5 sec. Do not plug
> in the TW during idle as a precaution.
> Sorry I can't explain why fuel pressure drops in hot engine
> compartment. Fuel Pressure Reg fails by allowing too much fuel to seep
> back to tank. Disconnect vacuum hose is not good diagnose. Clamp fuel
> return line. Other unconventional: You could remove fuel bleed bolt
> in fuel rail and observe pressure by the amount of squirts (on stopped
> engine.)
> If fuel has evaporated in fuel line or rail then it will take less
> than a sec to refill the them.
>
> 1. "There is not enough air comming in when starting?" what air?

It needs to be the correct ratio of fuel and AIR in cylinder for engine to
work. Air can come in three ways to main throttle body:
1. with throttle valve opened
2. through idle valve
3. through fast idle valve

2. "...and it started ok?" Did you mean symptom had dissapeared?

I ment it had a little higher RPMs in idle than normal but it started
immediately without cranking for 2-4 cranks before starting like it
does when it starts poorely.

> > I tried disconnecting vacum hose going from throttle body
> > to fuel pressure regulator, and it started ok
> > ==>>> There is not enough air comming in when starting
> >
> > I then saw then adjusted idle air speed (RPM) which were
> > too low, and I'll see today if that was the problem.

I adjusted (increased) idle speed and it has started ok
(I checked it twice since I changed idle speed), I belive
that has been my problem.
I'll post again if it begins to work poorely, but the
temperatures here will drop as from tomorrow and I
probably won't be able to test it anymore this year.

Thanx, for comments to all that have commented to this post.