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Old 17 Jul 2004, 03:45 pm
M
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Default Suddenly, after warm-up: bouncing idle and overheating???

Hi. I'm baffled. I was planning (still am) to lend this car to a
friend of mine in school who really needs a car. Any suggestions?

My '91 Accord LX was running like a champ, smooth and steady. This
morning, after not driving it for about two weeks, I started it and
let it warm up. For the first four or five minutes, it was idling
rock-steady at 1500RPM, typical for its warm weather warm-up.

The temp gauge started to climb, and once it reached the usual
temperature where the idle drops, it dropped. But instead of sitting
at the usual lower RPM, the idle instantly started jumping up and down
between 1100RPM and 1600RPM. Up, down, up, down. It was like a
metronome.

I pumped the gas a few times, and of course it revved, but it went
right back to bouncing. It seems that when I put it in gear, either
drive or reverse, it's perfectly steady again at the usual 600 or so
RPM in-gear idle. Put it back in park or in neutral, and it starts
bouncing again. One other brand new symptom to go along with this
behavior: after another 4 or 5 more minutes, the temperature gauge
suddenly starts climbing fast to overheat. I shut off the engine
before it gets there. Did notice that only the passenger-side
radiator fan appears to be running.

Tried restarting the car a number of times, with and without letting
it fully cool -- this behavior is consistent. Normal warm-up, idle
starts bouncing the instant it drops the first time, 4 or 5 more
minutes go by, then the engine starts to overheat.

Help?! Many thanks for advice. (Besides, "take it in!" Yes, I'll do
that if I have to.) Please post your idea(s) in this forum.
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Old 18 Jul 2004, 03:23 am
Eric
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Default Re: Suddenly, after warm-up: bouncing idle and overheating???

M wrote:
>
> Hi. I'm baffled. I was planning (still am) to lend this car to a
> friend of mine in school who really needs a car. Any suggestions?
>
> My '91 Accord LX was running like a champ, smooth and steady. This
> morning, after not driving it for about two weeks, I started it and
> let it warm up. For the first four or five minutes, it was idling
> rock-steady at 1500RPM, typical for its warm weather warm-up.
>
> The temp gauge started to climb, and once it reached the usual
> temperature where the idle drops, it dropped. But instead of sitting
> at the usual lower RPM, the idle instantly started jumping up and down
> between 1100RPM and 1600RPM. Up, down, up, down. It was like a
> metronome.
>
> I pumped the gas a few times, and of course it revved, but it went
> right back to bouncing. It seems that when I put it in gear, either
> drive or reverse, it's perfectly steady again at the usual 600 or so
> RPM in-gear idle. Put it back in park or in neutral, and it starts
> bouncing again. One other brand new symptom to go along with this
> behavior: after another 4 or 5 more minutes, the temperature gauge
> suddenly starts climbing fast to overheat. I shut off the engine
> before it gets there. Did notice that only the passenger-side
> radiator fan appears to be running.
>
> Tried restarting the car a number of times, with and without letting
> it fully cool -- this behavior is consistent. Normal warm-up, idle
> starts bouncing the instant it drops the first time, 4 or 5 more
> minutes go by, then the engine starts to overheat.
>
> Help?! Many thanks for advice. (Besides, "take it in!" Yes, I'll do
> that if I have to.) Please post your idea(s) in this forum.


The info below is from one of my prior posts regarding an '88 Accord LXi.
The basic information still holds true for your '91. The link embedded in
the TinyURL link likely won't work right now since the
http://www.hondaautomotiveparts.com has been down most of the day (at least
I can't access it). The cold start valves are basically the same on the two
cars but they may be located in different places. If I remember correctly,
on the '91 Accord it's the valve which is the furthest on the right on the
front of the intake manifold as you're facing the engine and has two coolant
hoses going to it at the bottom.

[prior post]

The most common problem associated with the idle cycling up and down is
usually due to a lack of coolant flowing through the cold start valve. The
valve is item number 8 in this diagram http://tinyurl.com/xj18. If the
valve doesn't warm up as the engine warms up (from coolant flowing through
the bottom part), the PGMFI system will misinterpret the condition and idle
cycling results. The first thing to due is to check the valve and make
sure that the lower part of the valve gets hot as the engine warms up. If
the valve doesn't get hot, try bleeding the coolant and make sure that
coolant is flowing through the valve. You can double check the valve as a
source of the cycling by removing the two screws from the top along with
the oval shaped plate and push down on the inner valve/plunger in the
center. The cycling should stop if the valve is the problem. If the valve
is getting hot and pushing the inner plunger down stops the cycling, then
the valve likely needs to be replaced.

Eric
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  #3 (permalink)  
Old 18 Jul 2004, 04:39 am
Edmechanic
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Default Re: Suddenly, after warm-up: bouncing idle and overheating???

mitch_wny@yahoo.com (M) wrote in message news:<9db4ac93.0407171245.3ee799dc@posting.google. com>...
> Hi. I'm baffled. I was planning (still am) to lend this car to a
> friend of mine in school who really needs a car. Any suggestions?
>
> My '91 Accord LX was running like a champ, smooth and steady. This
> morning, after not driving it for about two weeks, I started it and
> let it warm up. For the first four or five minutes, it was idling
> rock-steady at 1500RPM, typical for its warm weather warm-up.
>
> The temp gauge started to climb, and once it reached the usual
> temperature where the idle drops, it dropped. But instead of sitting
> at the usual lower RPM, the idle instantly started jumping up and down
> between 1100RPM and 1600RPM. Up, down, up, down. It was like a
> metronome.
>
> I pumped the gas a few times, and of course it revved, but it went
> right back to bouncing. It seems that when I put it in gear, either
> drive or reverse, it's perfectly steady again at the usual 600 or so
> RPM in-gear idle. Put it back in park or in neutral, and it starts
> bouncing again. One other brand new symptom to go along with this
> behavior: after another 4 or 5 more minutes, the temperature gauge
> suddenly starts climbing fast to overheat. I shut off the engine
> before it gets there. Did notice that only the passenger-side
> radiator fan appears to be running.
>
> Tried restarting the car a number of times, with and without letting
> it fully cool -- this behavior is consistent. Normal warm-up, idle
> starts bouncing the instant it drops the first time, 4 or 5 more
> minutes go by, then the engine starts to overheat.
>
> Help?! Many thanks for advice. (Besides, "take it in!" Yes, I'll do
> that if I have to.) Please post your idea(s) in this forum.


Well I think many things could cause a fluctuating idle but the
overheating sounds ominous to me. I suspect a blown head gasket.
Unscrew the oil filler cap and look for chocolate milk like residue
(coolant in oil), also look at oil dipstick for chocolate milk. Also
take out spark plugs and look at firing tips. Look for plugs that are
inconsistent with others, greenish tint on insulator is coolant, also
steamed clean look is bad sign.
When engine is cold, remove radiator cap and look for oil, also
leave cap off of cold engine and start it, if coolant shoots out right
away could be combustion gases leaking into coolant system, probably
at cylinder head.
If this fails to find anything then concentrate on overheating.
Is it a bad thermostat, clogged radiator, bad water pump(eroded
blades), or maybe a jumped timing belt.
A secret of good mechanics is that they can feel a missfire also.
Also your varying idle and overheating could be due to an airleak
.. An airleak could cause a varying idle and might smooth out with
higher rpm. And a lean mixture runs hotter but in my experience not a
real fast overheat.
Hope this helps
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  #4 (permalink)  
Old 19 Jul 2004, 05:42 am
Eric
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Posts: n/a
Default Re: Suddenly, after warm-up: bouncing idle and overheating???

OK, here's the a link for a picture depicting the valve for a '91 Accord,
http://tinyurl.com/5yuk8. Honda lists it as a fast idle valve, item #8 in
the diagram. This diagram shows the coolant hoses going to the fast idle
valve, http://tinyurl.com/5ht67. If there's air trapped in the system, then
it could block coolant flowing through this valve. Low coolant could also
explain your overheating symptoms. You need to bleed the coolant using the
coolant bleeder valve which is on top of the thermostat housing. Once
you've done this and topped up the coolant to the correct level, you'll need
to check the operation of the valve as in my prior post. Note that blocked
coolant flow through this valve can also occur for other reasons besides low
coolant. On one car I discovered rust plugging up the coolant passages in
the electronic air control valve (EACV) which sits just to the left of the
fast idle valve.

Eric
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Old 19 Jul 2004, 02:56 pm
Jason
Guest
 
Posts: n/a
Default Re: Suddenly, after warm-up: bouncing idle and overheating???

In article <40FBA5A4.130BD4F7@spam.now>, say.no@spam.now wrote:

> OK, here's the a link for a picture depicting the valve for a '91 Accord,
> http://tinyurl.com/5yuk8. Honda lists it as a fast idle valve, item #8 in
> the diagram. This diagram shows the coolant hoses going to the fast idle
> valve, http://tinyurl.com/5ht67. If there's air trapped in the system, then
> it could block coolant flowing through this valve. Low coolant could also
> explain your overheating symptoms. You need to bleed the coolant using the
> coolant bleeder valve which is on top of the thermostat housing. Once
> you've done this and topped up the coolant to the correct level, you'll need
> to check the operation of the valve as in my prior post. Note that blocked
> coolant flow through this valve can also occur for other reasons besides low
> coolant. On one car I discovered rust plugging up the coolant passages in
> the electronic air control valve (EACV) which sits just to the left of the
> fast idle valve.
>
> Eric


Eric,
Excellent two posts. Keep up the great work.

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