When my 91 Integra is idling, the RPM's are going up and down from
1500-2200 RPM,....like it the car is breathing....:). This started just
this weekend. Also noticed my temp gauge stopped working when this
weird idling began or maybe the weird idling started when the temp guage
stopped working. The temp needle stays on C, never raises to operating
temp. I also noticed the heater air temp, is not as warm/hot as it
normally is. The car runs fine other than the weird idling.
I suspect a faulty temp sensor/sending unit or a faulty thermostat,
causing the idle issue.
What do you think Tegger?....or anyone else.
As Groucho said: "Why, a four year-old boy could understand this".
Your reservoir and radiator are mostly empty. Don't drive it anywhere or
you might crack your head. Fill them both with Honda premix and then
keep topping up the reservoir to the MAX mark for a couple more mornings
until is stops 'sipping' coolant as the AIR is purged. It will solve
your immediate problems. There's more to purging air from a '91 Teg, but
this will get you out of the woods.
> I guess I should have mentioned, I check the obvious Friday when the
Then it must be just AIR, since the sensors have to be immersed or they
will give the symptoms you describe. Are you sure nobody has been
working on your cooling system recently ?
I'd suspect a faulty thermostat before anything else.
The ECU and the dash gause use different sensors. It would be unlikely for
both to fail at teh same time.
Try replacing the thermostat with new OEM. Do not use aftermarket.
As for the dash gauge... the sender is a single-wire unit under the
distributor. Make sure that's hooked up and the wire isn't broken.
Fluctuating idle can also be caused by neglected coolant changes. The Fast
Idle valve sticks open, leading to excessive air when hot. There is a way
to test for that.
No. I first dicovered the issue Friday when I went to lunch. Cranked
the car....cold... up and down idling. When car gets hot, no
difference. HOwever once, while driving the weekend, I noticed the temp
needle had started working and was registering normal operating temp.
When I stopped at stoplight, car idled normal.
This temp gauge starting to work only occurred once all weekend.
I was mistaken when I replied earlier the problem occurred when the
engine was cold also. Today I have found that the bouncing idle issue
only occurs after the engine gets warm a few minutes after starting, at
the same time the temp gauge is not working...reading C. Again today the
temp gauge started working while I was driving. When I came to a stop,
the car idled just fine. That is the second time I have seen this happen.
I am still inclined to believe the temp guage not working is related to
the bouncing idle issue. I guess I can start by replacing the
thermostat, probably the cheapest place to start
The coolant was changed in the vehicle about 6 months ago when I had the
timing belt and water pump replaced, so no coolant neglect.
Why? The temp gauge is not connected to the ECU in any way.
The ECU uses a separate Engine Coolant Temp(ECT) sensor.(2-wire thermistor)
The gauge temp sensor is a one-wire sensor,and not in the same location.
while you have the TS housing off,you might as well measure the engine
coolant temp (ECT) sensor resistance.it should read 2000 ohms at 68
degF.(mine read 0;open) at boiling,it should read ~400 ohms.
Those numbers are from my 94-01 Integra Haynes manual)
Some Honda motors(like my 94 Integra B-18 motor) have an air-bleed port to
remove all the air from the block.
If the coolant is not covering the ECT,it can cause idle problems.
It is a 5spd manual.
Just drove the car out to dinner. On the way there, the temp gauge
worked, and car idled just fine. However, it seems the temp guage maybe
registering slightly cooler than usual.
On the way home, temp gauge tried to register, but never left just about
the left had mark. Idle bounced slightly, but not as bad as earlier today.
I'm frankly at a total loss to explain the apparent connection between your
temperature gauge and the bouncing idle.
The temp gauge/sender and the EACV are on totally different circuits, with
different fuses and connectors. The EACV is the ONLY electrical component
on your car that has anything remotely to do with the idle.
I can only conclude that
1) it's a bizarre coincidence,
2) there are aftermarket intrusions into the wiring which are poorly made,
3) there is corrosion on the ECU connectors, causing shorts between wires
Have you looked at the ECU to see if it's nice and shiny clean?
With the idle fluctuating, remove the air intake pipe from air cleaner to
throttle body. Cover the LOWER port in the throttle body with your finger.
Does the idle settle down?
Update.. no stored ECU codes. After today, I am now convinced it is
probably the thermostat. Today when driving going to lunch the temp
needle moved off C a little bit. The bouncy idle was alot less when
stopped. On the way home, the temp needle eventually moved up to normal
operating temperature, no bouncy idle at all.
Suspect thermostat is intermittently sticking and causing engine to run
colder. Now do I change it myself or take it to my mechanic. I have
read on the Acura forums the 3 bolts to remove the thermostat are a
bitch to get to. Some have changed it in 30mins, some 2hour+ due to the
It's pretty easy, actually. I think those "2hour+" reports may be the
experiences of less-than-qualified individuals.
The only real problem is that room is a bit tight. You need to remove the
big black air intake pipe for access.
That third bolt is for the ECU ground; the other two bolts actually hold
the housing on. They are diametrically opposed; the third one is towards
The bolts are 10mm or 12mm, as I recall. One will take a socket, the other
may need a short wrench. The kind of wrench that has a a ratchet in the
closed end is very helpful.
Use a worn screwdriver to scrape corrosion off the lips of the housing
halves before you install the new 'stat.
If you're even remotely mechanically inclined, this is no more difficult
than changing your own oil.
A tip though: Use an OEM thermostat and gasket!!!!
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