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High Idle

My Galant started idling really high the other day. It stays pretty steady at about 3000 RPMs. Today I check the butterfly valve in the throttle body, it was fine. Then I checked the resistance on the IAC and it checked out fine. It does not smell like it's running rich just really high idle. The idle does drop while in gear but it still doesn't go down to "normal". Thanks in advance any and all advice is appreciated. John
 

Yes the engine gets up to temp. I drove it to and from work yesterday (about a 30 minute drive) and it idled high at every stop and when I pulled in the parking lot.
 

AnotherNewb

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I know this sounds dumb but check and make sure the biss screw is still in the throttle body, after that make sure none of the vacuum lines are cracked, don't forget about the brake booster hose.
 

What exactly is the "biss screw" I am unfamiliar with it. Also, I have checked over all the vacuum lines and didn't notice anything, I will give them all a twice over tomorrow.
 

AnotherNewb

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Wow your fast. I've had biss screws blow out of the throttle body and cause a steady high ldle out of the blue.
 

Thanks for the info. The biss screw is still in my car though. Is it possible it is out of adjustment? Should I try readjusting it or should I just leave it alone? Once again I appreciate all the information.
 

raptorWagon

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Quoting yaretheytaken:
Yes the engine gets up to temp. I drove it to and from work yesterday (about a 30 minute drive) and it idled high at every stop and when I pulled in the parking lot.


It warms up, but does it get hot? When was the last time you checked your coolant level? I had a similar situation, come to find I had a coolant leak. Had a high idle later on down the road that was related to my cruise control though. It could be a number of things, if it's getting hot, check your coolant level and possibly replace your thermostat as it could be stuck shut.
 

I was looking at my Galant today and there is a sensor right by the throttle. It is fairly small and has one wire. Can anyone tell me what this is and if that could cause this issue? I'm going to try the biss adjustment soon. Thanks again.
 

AnotherNewb

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If its the one wire switch on the fire wall side of the tb then its the throttle closed switch.
 

Yes it is on the fire wall side of the tb. If the throttle closed switch were to malfunction could it cause the problem I am experiencing. Also, how would I go about testing it. One more thing the reason I brought it up is because there is a metal nub on the underside of this senser and it is protruding outward and my throttle rests on this. Is that normal?
 

AnotherNewb

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The nub you are talking about is supposed to be touching the buttryfly pulley. When the throttle is closed, The connector on top should be grounded. I don't believe it is the cause of your high idle. Since it stays steady I would make sure that the engine fully comes up to temperature that will eliminate a thermostat causing the car to stay in high idle mode. Next be sure that there are no major vacuum leaks, a boost leak test will help greatly there. If you still can't find it my next move would be to block off the fiav. Only things I can really think of that would cause high idle but not idle surge.
 

vtecds1

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- test
- Check to see if your throttle cable is too tight.
- Test your TPS
 
Last edited:

AnotherNewb

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Everytime I read your name I want to talk like a pirate. Yare they be taken below deck and put in shackles /ubbthreads/images/graemlins/grin.gif
 

desant78

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Quoting AnotherNewb:
The nub you are talking about is supposed to be touching the buttryfly pulley. When the throttle is closed, The connector on top should be grounded. I don't believe it is the cause of your high idle. Since it stays steady I would make sure that the engine fully comes up to temperature that will eliminate a thermostat causing the car to stay in high idle mode. Next be sure that there are no major vacuum leaks, a boost leak test will help greatly there. If you still can't find it my next move would be to block off the fiav. Only things I can really think of that would cause high idle but not idle surge.



disconnecting mine drastically increases my idle.

I have a few questions for you though.

1. is your coolant still run through your throttle body? - this would be a FIAV issue

2. is your coolant temps still plugged in? check the sensor make sure it is properly hooked up. if a ground falls off, this will cause your idle to increase also. NOTE: even if your guage temp is working, this does not mean the ecu is recieving a signal from the coolant temp sensor

3. DEF check the TPS. even though I found this doesn't usually result in an increase of 2000 rpm, still very important.

4. Do you have an A/F gauge? if not hook up a volt meter to your 02 sensor. At idle when your car is warm, it should be running from lean to rich (roughly 0 to 1v) oscillating between the two. All of the above will cause the car to run rich, raise the idle, and the 02 sensor will tell that by just giving a reading close to 1v, and being relatively steady.


if all else fails, check for a boast leak. The FIAV should be blocked off if it hasn't been and no coolant is running through it...even if there is coolant. After 20 years they begin to fail. Also I have heard of the coolant temp sensor failing, resulting in this issue.

the engine uses a combination of the engine temperature, TPS, and the switch that is an on/off, it was mentioned above. it is hit when the u release the throttle. Lastly the ecu uses hte MAF to know the air coming in to achieve a low smooth idle. ANYTHING affecting the above will mess with your idle.


hope this helps! i've been through hell and back w/ this issue...i'm pretty sure it's a right of passage in order to own one of these cars.
 

stealthtt24

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Quoting AnotherNewb:
Everytime I read your name I want to talk like a pirate. Yare they be taken below deck and put in shackles /ubbthreads/images/graemlins/grin.gif



I loled for about 5 minutes.
 

beaner

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b'ham, mi
You probably have a huge intake leak after the tb. Also try swapping ecus and checking the coolant temp sensor. Good luck.
 
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