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Sporadic idle


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Car: 2008 Legacy 2.5i 5MT

 

Issue: When in traffic lately, and I push in the clutch the RPM jump up to 1500 and then rise to about 1850 then drop to 950 then rise up again to 1500. If I coast in neutral with my foot off the clutch this does not occur only when in gear and the clutch pressed in.

 

While this is occurring (the high idle) if I knock it out of gear and let my foot off the clutch it will return to normal idle.

 

Causes: IACV? TB malfunction? Vacuum ? Im not sure where to start b/c i dont have any CELs. Regularly maintained (oil every 4K, air filter every 8K, plugs every 20K)

 

If you have insight to this problem please let me know :redface:

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is the AC on when this is happening?

 

No AC, and there is a rev match for upshifts. I was thinking about this feature as the culprit. I think the ECU or the TCU thinks it needs to hold or raise the RPM.

 

Could be the clutch switch in the pedal assembly ? :confused:

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Check the spark plugs/spark plug leads. A loose one at the spark plug end will cause some erratic idle issues, and ECU will try to compensate. Won't trigger a CEL either. If a lead *is* loose, check the spark plug itself to make sure it's in snug.

 

Otherwise, it's most likely a vacuum leak. There's a lot of minor things that can happen that won't trigger a CEL on the 2.5i's, they are not that finicky about them.

 

Regards,

 

Paul Hansen

http://www.avoturboworld.com/avoshop

http://www.facebook.com/avoturboworld

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Check the spark plugs/spark plug leads. A loose one at the spark plug end will cause some erratic idle issues, and ECU will try to compensate. Won't trigger a CEL either. If a lead *is* loose, check the spark plug itself to make sure it's in snug.

 

Otherwise, it's most likely a vacuum leak. There's a lot of minor things that can happen that won't trigger a CEL on the 2.5i's, they are not that finicky about them.

 

Regards,

 

Paul Hansen

http://www.avoturboworld.com/avoshop

http://www.facebook.com/avoturboworld

 

Yeah it is almost time for a plug change anyhow so ill do them this weekend. As far as vacuum, should i check all the lines on the IM ?

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