need help fixing idle speed

L

lawdoc

New Member

May 31, 2009

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Feb 27, 2010

#1

• Feb 27, 2010

• #1

I have a '88 5.0 HO Lx. It has developed a high idle, right at around 12-1300. but if i leave it idle for a while, at a stop light for instance 5-10 minutes the idle will fall and level at around 7-1000. What can cause this. I've checked my timing it is on the line and my vacuum is also steady and in range. The only thing i can think of is that maybe the spout chip is bad but i don't know how to check it. Also the maybe the tps but i cant remember how to check that either please help.

 

tannerc91gt

This last 25% is foreign territory at this point

Founding Member

Nov 29, 1999

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Indiana

Feb 27, 2010

#2

• Feb 27, 2010

• #2

Clean the idle air control motor. 1000 is way high for idling they like the 650-800 range.
Push comes to shove, adjust the idle set screw to lower the idle

 

HISSIN50

"How long does it take to get help in here?

15 Year Member

Nov 29, 1999

31,179

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Feb 27, 2010

#3

• Feb 27, 2010

• #3

Pull codes and look for a vac line that has cracked or come off. A small leak won't drop your manifold vac reading much but can affect the idle.

 

N

njoliver

Member

Nov 25, 2009

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Columbus OH

Feb 27, 2010

#4

• Feb 27, 2010

• #4

tannerc91gt said:

Clean the idle air control motor. 1000 is way high for idling they like the 650-800 range.
Push comes to shove, adjust the idle set screw to lower the idle

Click to expand...

if it was idling normal before you should not touch idle screw as this might just be covering up a problem. you should never have to adjust idle screw, unless you have adjusted it in the pass. clean and check IAC,

 

M

Mopar1

Member

Oct 28, 2002

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Shelton, WA

Feb 28, 2010

#5

• Feb 28, 2010

• #5

HISSIN50 said:

Pull codes and look for a vac line that has cracked or come off. A small leak won't drop your manifold vac reading much but can affect the idle.

Click to expand...

Ditto. Mine would idle at 700 then shoot to 1200 or so after a few minutes, then back down to 700. Drove me nuts. Discover a split vac line in the upper intake. I couldnt even see it. I think it was starter fluid I used to find it. Frustrating as hell.

 

Mustang5L5

That is…until I whipped out my Bissell

Mod Dude

Feb 18, 2001

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Feb 28, 2010

#6

• Feb 28, 2010

• #6

Pull the codes