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Omn3d0n
 
Join Date: Jan 2009
Location: Midwest
Posts: 8
Angry Hunting idle, not a vacuum leak..Help...

Hi,

I have a 83 Spec 944 race car.
I've been having some issues
related to the car stalling and idling weird.
The shop has done the following.

1. Replace speed and ref sensors.
2. Replace DME relay
3. Replace engine harness.
4. Rewired secondary harness.
6. Vacuum hoses.

Still had the issue. Decided to
replace the DME and MAF with a later
(86) model one. The car runs better
and smoother.

It now has runs at idle smoothly,
but intermittently will either
drop or jump idle. When the car
is above around 1600 rpms, it does
not seem to do it.

Is this an ISV problem? Anything else
I should check?

Thanks
Sid
Old 09-27-2009, 01:44 PM
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mikepellegrini's Avatar
 
Join Date: Sep 2007
Location: Tacoma, WA
Posts: 1,856
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I have kinda the same thing on my 83 NA - occasionally, not always, the idle will drop and then come back. It acts just like when you take the vacuum line off the FPR. It'll drop to about 600 RPM, then come back - over and over and over.

But the really - really weird thing with mine - you turn on the A/C and it'll stop. Almost every time. The idle becomes rock solid again.

I can't imagine the relationship between turning the A/C on, and a vacuum problem (or whatever it is) but it really does exist. I can repeat the "fix" over and over - it almost always will make it quit dropping out.

It started this dropping out only after I had the intake manifold off, so I assumed it was vacuum related.

I ran a line direct from the throttle body to the FPR and it still does it, so I guess it isn't that.

I haven't done any more checking because the car runs just fine, otherwise. More of an annoyance than anything else. But it would be nice if I could get rid of it.

Maybe it is the ISV?
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83 944 NA - Black on black
86 951 - Red
97 Ford Expedition

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Old 09-27-2009, 04:50 PM
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Join Date: Mar 2012
Posts: 9
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Ive been having this same issue (with the exception of the strange a/c fix). can someone please tell me the procedure to replacing all the vaccuum lines / how difficult it is to do?
Old 04-06-2012, 08:29 AM
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Location: Orlando area
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Replacing the vacuum lines is no big deal. Clarks Garage has a map of where it all goes. Most people are going to silicone lines. A question for you all here: When you checked the vacuum system for leaks did you get to everything? Three places that frequently get missed are the t fitting under the j boot. It feeds the idle stabilizer and something else but I can't recall what. Second is the Vacuum Cannister next to the battery. Third is the throttle body shaft seals. They're tiny and rubber and definitely do cause leaks. I found mine using the air pressure into the j boot and soapy water solution sprayed on everything.
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3 944's, 2 Boxsters and one Caman S, and now one 951 turbo. Really miss the Cayman.

Some people try to turn back their "odometers." Not me. I want people to know 'why' I look this way. I've traveled a long way and some of the roads weren't paved.
Old 04-06-2012, 08:39 AM
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yea i just found that my T fitting was unhooked! thankyou very much for this help. also, when looking at the engine from in front of the car, there are vacuum lines running to a device in the upper right corner. Its right on the firewall, in the corner in front of the driver. when I remove the line on top, the car idles higher and smoother.. what is this, and why would that happen?
Old 04-06-2012, 02:11 PM
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