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Join Date: Aug 2006
Location: Atlanta, GA
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Elevated & Surging Idle on 3.2 Ideas?

This is new. Normal idle has been 900 to 1000 rpm. All of sudden that has elevated to 1,200 with a regular cycle/pulse up to 1,300 and back to 1,200 every few seconds. What would cause this?

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Old 07-14-2011, 04:14 PM
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Have you check the throttle linkage to see if anything is binding? Is the Idle Switch connecting/clicking at rest?

Tap on the ICV to see if settles down.

Check the vacuum Y lines behind the TB to either side to those bell diaphrams ( one being the FPR ). My buddy's 86 was disconected on the passenger side one.
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Last edited by DRACO A5OG; 07-14-2011 at 04:32 PM..
Old 07-14-2011, 04:22 PM
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Check the torque values on the intake manifold-to-cylinder head nuts. These have a tendency to loosen due to thermal cycling. I had an unstable idle on my 1988 3.2; checked the torque on said nuts and most were only finger tight. A re-torque to the service manual value cured the idle instability.
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Old 07-14-2011, 04:24 PM
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Quote:
Check the torque values on the intake manifold-to-cylinder head nuts. These have a tendency to loosen due to thermal cycling. I had an unstable idle on my 1988 3.2; checked the torque on said nuts and most were only finger tight. A re-torque to the service manual value cured the idle instability.
Good suggestion. I changed out the intake gaskets and spacers over a year ago and have not retorqed since. Py previous intake leak symptom was a rough idle but who knows.
Old 07-14-2011, 05:38 PM
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Quote:
Have you check the throttle linkage to see if anything is binding? Is the Idle Switch connecting/clicking at rest?



Tap on the ICV to see if settles down.



Check the vacuum Y lines behind the TB to either side to those bell diaphrams ( one being the FPR ). My buddy's 86 was disconected on the passenger side one.
Thanks for the ideas! I will check all of these items.
Old 07-14-2011, 05:40 PM
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Quote:
Originally Posted by mthomas58 View Post
Good suggestion. I changed out the intake gaskets and spacers over a year ago and have not retorqed since. Py previous intake leak symptom was a rough idle but who knows.
As I understand it it should be re-torqued after 2000 miles, but would a leak cause a lean/low idle situation?
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Old 07-14-2011, 06:25 PM
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A rich condition due to a bad 02 sensor might cause this too.
Old 07-15-2011, 07:23 AM
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Don't forget Fuel injector's too. If they are original, it's time to send them out to be overhauled!!!!!
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Old 07-15-2011, 07:27 AM
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Idle switch
Old 07-15-2011, 08:03 AM
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Had a similar problem. A mixture adjustment solved it.
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Old 07-15-2011, 08:13 AM
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All good suggestions. Due to the sudden onset, I'd pull the icv when warm, and re-connect the elec - make sure the valve is half open. Be sure that it moves freely.
Old 07-15-2011, 09:34 AM
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Quote:
Originally Posted by PatrickB View Post
Don't forget Fuel injector's too. If they are original, it's time to send them out to be overhauled!!!!!
Sorry to hijack, but I have often wondered when this should be done. Is there a factory recc'd service interval for the injectors?

Re the idle, there have been a lot of threads on this (3.2s seem prone to bouncy idle).
So use the search button too as this problem can have multiple causes.
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Old 07-15-2011, 10:14 AM
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Injectors are good. All sent to Witchhunter for reconditioning at time of engine swap 2 yearss ago.

Problem appears to be intermittent. Did it again this morning on the way to work. Not out to lunch and not on the drive home
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Old 07-15-2011, 04:12 PM
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Idle issues

If none of the above resolve your issue:

1. Remove and clean the ICV, and reset the idle by shorting the connector
located on the engine compartment fuse panel as per the Bentley.

2. check for a disconnected/defective vaccum line.








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Old 07-15-2011, 04:39 PM
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Great pics Gerry
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Old 07-15-2011, 06:57 PM
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In the last picture there is a braided vacuum line next to the rubber ones and just above the "Y" vacuum lines, can anyone tell me where this line goes to or comes from? I finally had some time to check stuff out (crappy idle and idling very rich with no response from air fuel mix adjustment. Found the "Y" pulled off and the braided line missing (or maybe fallen down somewhere I can't see). There is a braided line over by the oil filler tube that goes down behind the engine

Quote:
Originally Posted by 86 911 Targa View Post
If none of the above resolve your issue:

1. Remove and clean the ICV, and reset the idle by shorting the connector
located on the engine compartment fuse panel as per the Bentley.

2. check for a disconnected/defective vaccum line.









Old 07-17-2011, 02:39 PM
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