Cause of vacuum flutter at idle? - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars
 
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post #1 of 5 (permalink) Old 07-31-06, 12:41 PM Thread Starter
Sir Boost-a-Lot
 
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Question Cause of vacuum flutter at idle?

It flutters rapidly and constantly at idle (1000rpm).

What could cause it?

The current cam is very mild. The motor doesn’t smoke but does seem down on power. I don’t hear any mechanical noises that are out of the ordinary.

Did I burn a valve?
Could a misfire cause this?


JL
1973 Cougar XR-7 convertible - 351C, 9:1 CR, 2V heads, Crower Ultra Beast, Weiand X–CELerator, 600CFM Edelbrock Performer, Dynamax long tubes, stock FMX, 3.89s w/ Detroit Locker
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post #2 of 5 (permalink) Old 07-31-06, 06:11 PM
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Re: Cause of vacuum flutter at idle?

Try a compression test, if you blew head gasket between 2 cyls it will flutter pretty bad and loose power...
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post #3 of 5 (permalink) Old 08-01-06, 01:20 AM
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Re: Cause of vacuum flutter at idle?

Possibly a few wiped lobes?
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post #4 of 5 (permalink) Old 08-01-06, 01:22 AM
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Re: Cause of vacuum flutter at idle?

I would also check the PCV valve located at the back of the driver side rocker cover. Sometimes at idle the bearing inside the valve does not sit still and may cause a vacume leak.....
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post #5 of 5 (permalink) Old 08-01-06, 05:53 AM Thread Starter
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Re: Cause of vacuum flutter at idle?

Update,
I forgot to mention that the car had rarely been started in the last 3 years.

Anyway, I changed the oil which had few miles put still managed to look black and nasty. As soon as I started it up, surprisingly it sounded better. I hooked up the vacuum gauge and to my surprise there is now next to no flutter.

After a quick spin around the block, it feels like it had more power too. It still needs to be tuned with the wideband, but I think my problem is largely resolved.

Could the crappy oil have prevented a lifter from pumping up?

Or was a spring or valve bound up from all of the sitting?

What do you guys think?

Thanks for your help.

JL
1973 Cougar XR-7 convertible - 351C, 9:1 CR, 2V heads, Crower Ultra Beast, Weiand X–CELerator, 600CFM Edelbrock Performer, Dynamax long tubes, stock FMX, 3.89s w/ Detroit Locker
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