Idle problems

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Jan 3, 2017 | 03:18 PM

brian.b

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Cross-Country

Joined: Jun 2012

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Idle problems

Hey guys I was wondering I have a 92 f 150 extended cab long bed 4x4 with a 302 5 speed.....well it idles up and down sometimes then sometimes it doesn't want to idle at all or high idle......then sometimes it's perfect.......any ideas.....

Jan 3, 2017 | 05:14 PM

timbersteel

Logistics Pro

Joined: Mar 2005

Posts: 4,698

Likes: 47

From: Mexico, Missouri

Quote:

Originally Posted by brian.b

First thing is to Check for Stored codes. It's as simple as using a paperclip and counting the flashes.

Do a search on here or Google and there is a plethora of information on how to and I'm sure video's.

Your wallet will thank you before throwing any parts at it.

Jan 3, 2017 | 05:17 PM

PRIMERED79 SHORT BED

Laughing Gas

Joined: Jan 2012

Posts: 1,106

Likes: 25

Check for vacuum leaks and check the TPS voltage.
Should be less than 1volt.
Also see if your IAC needs to be cleaned out.

Jan 4, 2017 | 12:06 PM

brian.b

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Cross-Country

Joined: Jun 2012

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i read the codes today and got this ......21.....24...29....33....67.......what would be going on here .......

Jan 4, 2017 | 01:04 PM

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,780

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From: Kentucky

Quote:

Originally Posted by brian.b

i read the codes today and got this ......21.....24...29....33....67.......what would be going on here .......

Codes 21,24 indicate the truck was not fully warmed up before running the Key On Engine Off (KOEO) tests.

Code 21: ECT out of self test range 0.3 to 3.7 volts.
Code 24: ACT sensor out of self test range 0.3 to 3.7 volts.

Code 67 (KOEO): A/C ON during the KOEO tests.

Stored Codes (CM)
Code 29: Insufficient input from vehicle speed sensor.

Indicates the VSS signal has been low at some point during operation.

Code 33 (CM): EGR valve opening not detected.

Indicates the EGR feedback has not changed when the EGR was commanded open by the computer at some point during operation.

Jan 4, 2017 | 04:26 PM

brian.b

Thread Starter

Cross-Country

Joined: Jun 2012

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Quote:

Originally Posted by rla2005

ok I did the test with the engine cold......and the speedometer doesent work would that be the vss ......now what would cause the get to not open and would that cause it to idle weird.....it goes up sometimes down then sometimes it runs perfect......

Jan 6, 2017 | 09:37 AM

rla2005

Fleet Owner

Joined: Oct 2005

Posts: 20,780

Likes: 1,746

From: Kentucky

Quote:

Originally Posted by brian.b

It's possible a faulty VSS input could influence the PCM to change the pulse width duty cycle to the IAC, but not when the vehicle is at rest. A sticking or faulty IAC can also cause idle issues.

A rolling idle can also be caused by a faulty TPS (even though it may not flag a code), worn throttlebody or worn throttlebody blade shaft bushings as well as previously mentioned vacuum leaks.