Engine High Idle (2k)

1989LXFOX

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Jan 19, 2018
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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
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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
 
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1989LXFOX

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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!
 

1989LXFOX

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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.
 

1989LXFOX

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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

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Nov 13, 1999
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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
 

1989LXFOX

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Jan 19, 2018
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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
 

jrichker

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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.
 
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1989LXFOX

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Jan 19, 2018
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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

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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...
 

1989LXFOX

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Jan 19, 2018
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Hey all..... way late on this but I think the problem was just a dirty MAF. Cleaned it and took car out. No idle surge to speak of and my check engine light came on WAY WAY less than normal!

Thanks everyone
 

2000xp8

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Aug 8, 2003
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What does your check engine came on way less than normal mean?

I hope you solved it, but I've yet to see a single case ever, where cleaning the mass air meter fixed anything.
 

General karthief

wonder how much it would cost to ship you a pair
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I feel he has not solved anything.
if you have a tire that repeatedly needs air is it fixed until you have to add air again?
if your check engine light comes on and then goes out you still have a problem.