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Rpms

  • Thread starter Thread starter 2vjordy
  • Start date Start date Sep 9, 2017
2

2vjordy

Active User
Jul 19, 2017
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Sep 9, 2017
#1
  • Sep 9, 2017
  • #1
My mustang rpms is staying at 2200 and won't go no lower I undid my cables and touched them that's what I heard to do but that didn't work...any ideas if a sensor or something and what sensor it would be
 

imp

Mustang Master
Jul 13, 2017
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83
Sep 9, 2017
#2
  • Sep 9, 2017
  • #2
2vjordy said:
My mustang rpms is staying at 2200 and won't go no lower I undid my cables and touched them that's what I heard to do but that didn't work...any ideas if a sensor or something and what sensor it would be
Click to expand...
Check for trouble codes. Consider stuck open Idle Air Control, or Throttle Plate (less likely). imp
 

wmburns

SN Certified Technician
Aug 14, 2009
5,892
514
204
Houston Texas
Sep 10, 2017
#3
  • Sep 10, 2017
  • #3
+1 on above.

To add, how about a common garden variety vacuum leak? Or bad IAC valve?

Here's some more information on how to trouble shoot.

Troubleshoot IAC idle problems 1996-2004
https://www.stangnet.com/mustang-forums/resources/troubleshoot-iac-idle-problems-1996-2004.13/

It might be handy to mention the model year of your Mustang. But likely this won't change the trouble shooting steps.
 
Reactions: imp
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2vjordy

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Jul 19, 2017
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Sep 11, 2017
#4
  • Sep 11, 2017
  • #4
I changed the iac and the idle is going back down now but when I drive and come to stop the rpms still wanna stay up for like 15 sec then goes down..do I have to do a idle re learn process or something ? Or was the valve not the fix I mean before I put the valve the rpms wouldn't go down at all now they do just takes like 15 sec
 

imp

Mustang Master
Jul 13, 2017
531
105
83
Sep 11, 2017
#5
  • Sep 11, 2017
  • #5
2vjordy said:
I changed the iac and the idle is going back down now but when I drive and come to stop the rpms still wanna stay up for like 15 sec then goes down..do I have to do a idle re learn process or something ? Or was the valve not the fix I mean before I put the valve the rpms wouldn't go down at all now they do just takes like 15 sec
Click to expand...
Starting to think vacuum leak some where, which PCM is still able to "overcome" in efforts to reach idle speed. imp
 
2

2vjordy

Active User
Jul 19, 2017
16
0
1
Sep 11, 2017
#6
  • Sep 11, 2017
  • #6
imp said:
Starting to think vacuum leak some where, which PCM is still able to "overcome" in efforts to reach idle speed. imp
Click to expand...
I'll check for a vacume leak tomorrow let you no how it goes thanks
 

Neuron

5 Year Member
Nov 6, 2016
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Sep 12, 2017
#7
  • Sep 12, 2017
  • #7
My '98 did the same exact thing(replaced with Motorcraft Part) but settled down after a couple of days and worked fine after that, maybe had to relearn the PCM?
 
2

2vjordy

Active User
Jul 19, 2017
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Sep 12, 2017
#8
  • Sep 12, 2017
  • #8
Does anyone no how to do a relearn process I heard you can let the car idle or something I'm not to sure
 

wmburns

SN Certified Technician
Aug 14, 2009
5,892
514
204
Houston Texas
Sep 12, 2017
#9
  • Sep 12, 2017
  • #9
2vjordy said:
I changed the iac and the idle is going back down now but when I drive and come to stop the rpms still wanna stay up for like 15 sec then goes down..
Click to expand...
Does the car's speedometer work? Why does this matter? Because it is NORMAL for the PCM to keep the idle slightly higher while the car is moving. The PCM will only select slow idle when the car is stopped.

Search on hanging idle as 1,000's have complained about it. The trick here is to understand the difference between a normal hanging idle and an abnormal hanging idle.

A 2,000 RPM idle isn't likely normal.

A 1200-1500 RPM idle while moving is normal.

Bottom line: IF the RPM eventually settles down to a normal slow idle that means that the IAC is working and is being commanded by the PCM.

Did you review any of the information provided in the trouble shooting IAC/idle link? Did you perform the IAC basic functionality test?

Regarding the relearning process. Is the battery and alternator in tip top shape? Have you driven the car for several days? If both are true then a working PCM has had more than enough time to re-learn.
 
2

2vjordy

Active User
Jul 19, 2017
16
0
1
Sep 12, 2017
#10
  • Sep 12, 2017
  • #10
wmburns said:
Does the car's speedometer work? Why does this matter? Because it is NORMAL for the PCM to keep the idle slightly higher while the car is moving. The PCM will only select slow idle when the car is stopped.

Search on hanging idle as 1,000's have complained about it. The trick here is to understand the difference between a normal hanging idle and an abnormal hanging idle.

A 2,000 RPM idle isn't likely normal.

A 1200-1500 RPM idle while moving is normal.

Bottom line: IF the RPM eventually settles down to a normal slow idle that means that the IAC is working and is being commanded by the PCM.

Did you review any of the information provided in the trouble shooting IAC/idle link?

Regarding the relearning process. Is the battery and alternator in tip top shape? Have you driven the car for several days? If both are true then a working PCM has had more than enough time to re-learn.
Click to expand...
I haven't driven it for several days yet and the idle is still high like that when not moving at all and even when coming to a stop sign or red light it's never stayed that high before
 

wmburns

SN Certified Technician
Aug 14, 2009
5,892
514
204
Houston Texas
Sep 12, 2017
#11
  • Sep 12, 2017
  • #11
Here's some information on an affordable Windows based ODB2 scanner. How can this help? With an ODB2 scanner it's possible to monitor the IAC duty cycle. A slight vacuum leak will show up as a lower than normal IAC duty cycle.

ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/

Or course having an ODB2 scanner will open up a world of other diagnostic information. Car repair will never be the same after you see what an ODB2 scanner really can do.
 
Reactions: imp
2

2vjordy

Active User
Jul 19, 2017
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Sep 12, 2017
#12
  • Sep 12, 2017
  • #12
I will check that out thanks
 

TangStang

Member
Sep 26, 2003
8
4
13
Sep 21, 2017
#13
  • Sep 21, 2017
  • #13
The PCM must relearn the IAC, but the TPS works in conjuction.
Check the output voltage. It should be no more than 1.0 volt.
These two sensors can fail together.
 
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