Engine High Idle (2k)

1989LXFOX

Active Member
Jan 19, 2018
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#1
Hello Stangnet,

My car recently started to idle high, a little over 2,000 at idle. The RPMs drop down when I engage a gear then climb normally while progressing through gears (5 speed manual). When I come to a light the idle goes to a little of 2k. The normal idle set by my mechanic last summer is a little over 1,000. This problem doesnt immediately happen and happened only once before about 4 months ago so I thought it was an isolated incident, just recently it has happened everytime I drive. However when I turn the car off and start it up again a short while later the problem temporarily stops - my car doesnt jump to 2k when I first start it and drive it.
I have no major mods - I had smog deleted last summer and a new gasket for throttle body put on at time, thats when my idle was set to a little over 1k.

Thanks in advance!
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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#2
Here is a link to the famous 'surging idle checklist ', it will show you how to check for codes and the proper way to adjust the idle screw, read it over first then do the steps one by one, don't skip around, it works! I'll tell ya, I recently used it at the shop I hang around at to straighten out an idle problem on a fox they worked on several times.
thanks @jrichker jric
http://forums.stangnet.com/showthread.php?t=698148
 

1989LXFOX

Active Member
Jan 19, 2018
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#3
Thanks Kartheif! I dont have the resources or time to perform all that. But that helps because I know now that I should just take it up to my mechanic cause I want it done quick!
 

Mustang5L5

Car used in adult film "Highway Gangbang-InDaButt"
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#4
Just as a source of information. When it idles up to 2K, if you unplug the IAC on the throttle body, does the idle drop down?
 

1989LXFOX

Active Member
Jan 19, 2018
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#5
Just as a source of information. When it idles up to 2K, if you unplug the IAC on the throttle body, does the idle drop down?
Let me give it a try tonight! I was going to try cleaning the 10 pin connectors too.
 

mikestang63

SN Certified Technician
Aug 27, 2012
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#8
unless you have a major cam in that car, the idle should not be 1000. Way to high. Sounds like the mechanic is masking another issue
 

1989LXFOX

Active Member
Jan 19, 2018
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#9
And what is meant by 'no major mods'?
The engine is stock. I have a BBK cold air intake, some gauges (including a vacuum gauge that is connected to an unused port on vacuum tree). Smog pump delete. Could it be a coincidence that my drivers side power window stopped working at the same time this problem got worse? The power locks and the passenger side power window both work, controlled by dirvers side power window switch.

Thats about it for engine mods.
 

Blown88GT

Founding Member
Nov 13, 1999
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#10
The engine is stock.

1. I have a BBK cold air intake, some gauges (including a vacuum gauge that is connected to an unused port on vacuum tree). Smog pump delete.
2. Could it be a coincidence that my drivers side power window stopped working at the same time this problem got worse? The power locks and the passenger side power window both work, controlled by dirvers side power window switch.

Thats about it for engine mods.
1. What is vacuum at idle? Original '89 Ford MAF?
2. Yes, coincidence. PW has nothing to do with PL
 

Boostedpimp

10 Year Member
May 8, 2003
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#11
Need a new mechanic simply because idling at a 1000 rpms isn't acceptable
 

1989LXFOX

Active Member
Jan 19, 2018
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#12
1. What is vacuum at idle? Original '89 Ford MAF?
2. Yes, coincidence. PW has nothing to do with PL
I will check the vacuum at idle when the issue is not happening and what the vacuum is when the surge starts. Yes stock MAF
 

Blown88GT

Founding Member
Nov 13, 1999
964
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Palm Beach Gardens, FL
#13
Check all the clamps on the cold air kit. You may have an air leak that's bypassing the MAF with unmetered air, i.e. between MAF & TB.
 

jrichker

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#14
Just as a source of information. When it idles up to 2K, if you unplug the IAC on the throttle body, does the idle drop down?


Good idea, if it does drop down then you have a sensor or wiring problem.

If it doesn't drop down, you have vacuum leak somewhere.

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix. :D

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
 

1989LXFOX

Active Member
Jan 19, 2018
33
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38
#15
Good idea, if it does drop down then you have a sensor or wiring problem.

If it doesn't drop down, you have vacuum leak somewhere.

You guys with idle/stall problems could save a lot of time chasing your tails if you would go through the Surging Idle Checklist. Over 50 different people contributed information to it. The first two posts have all the fixes, and steps through the how to find and fix your idle problems without spending a lot of time and money. It includes how to dump the computer codes quickly and simply as one of the first steps. I continue to update it as more people post fixes or ask questions. You can post questions to that sticky and have your name and idle problem recognized. The guys with original problems and fixes get their posts added to the main fix. :D

It's free, I don't get anything for the use of it except knowing I helped a fellow Mustang enthusiast with his car. At last check, it had more than 250,000 hits, which indicates it does help fix idle problems quickly and inexpensively.
Yes I am going to go throught hat check list. To answer your earlier question though about vacuum - When it began to surge my vacuum gauge read 22 inHg at idle
 

jrichker

StangNet's favorite TOOL
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Mar 10, 2000
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#16
Yes I am going to go throught hat check list. To answer your earlier question though about vacuum - When it began to surge my vacuum gauge read 22 inHg at idle
That pretty much eliminates a vacuum leak as being part of the problem...
 

Mustang5L5

Car used in adult film "Highway Gangbang-InDaButt"
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#17
Have you had a chance to pull the IAC plug when the idle is high?