Low idle/vacuum leak
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New User
Joined: Mar 2002
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From: monmouth US
Low idle/vacuum leak
Hi, I have a '97 expy with a 5.4. Recently it has had a very low idle and almost stalls(chug chug). There is also a vacuum leak somewhere around the throttle body or the EGR valve but I can't pinpont it, even though it's pretty loud. That is probably causing the low idle but I cant find the leak! Has anyone else had this problem?
Senior User
Joined: Feb 2002
Posts: 135
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Low idle/vacuum leak
>Hi, I have a '97 expy with a 5.4. Recently it has had a very
>low idle and almost stalls(chug chug). There is also a
>vacuum leak somewhere around the throttle body or the EGR
>valve but I can't pinpont it, even though it's pretty loud.
>That is probably causing the low idle but I cant find the
>leak! Has anyone else had this problem?
Is this noise a whistling noise?
John B.
1998 Expy 4.6
>low idle and almost stalls(chug chug). There is also a
>vacuum leak somewhere around the throttle body or the EGR
>valve but I can't pinpont it, even though it's pretty loud.
>That is probably causing the low idle but I cant find the
>leak! Has anyone else had this problem?
Is this noise a whistling noise?
John B.
1998 Expy 4.6
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New User
Joined: Mar 2002
Posts: 9
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From: monmouth US
Low idle/vacuum leak
It's more like a suction noise. I thought the gasket on the intake air control might be leaking,so this afternoon I took it off and cleaned it out with carb. cleaner and put gasket sealer on both sides of the gasket. My wife jumped in and took off before I had a chance to check it.
Elder User
Joined: Nov 2002
Posts: 736
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From: Texas, USA
Low idle/vacuum leak
Hi,
On the '97 there are numerous hoses attached to the air delivery system before it enters the throttle body as well as the throttle body itself. IF you don't have a stethoscope, get a peice of tubing about 1/2 in. by 3ft long. (old garden hose works well) Stick one end to your ear, the other poke around the engine until you find the source,which will be much louder when have put the end of the tube on it.
Check also the gasket around the airflow sensor and the temperature sensor where it plugs into the side of the air tube immediately upstream of the filter cannister.
Hope this helps.
On the '97 there are numerous hoses attached to the air delivery system before it enters the throttle body as well as the throttle body itself. IF you don't have a stethoscope, get a peice of tubing about 1/2 in. by 3ft long. (old garden hose works well) Stick one end to your ear, the other poke around the engine until you find the source,which will be much louder when have put the end of the tube on it.
Check also the gasket around the airflow sensor and the temperature sensor where it plugs into the side of the air tube immediately upstream of the filter cannister.
Hope this helps.
Thread Starter
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New User
Joined: Mar 2002
Posts: 9
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From: monmouth US
Low idle/vacuum leak
Well,I found the leak. It was the hose that goes from behind the IAC to the PCV valve. The right-angle rubber boot on the hose had a big crack in it. AutoZone did'nt have the boot(or anything that would work) so I made one out of a copper plumbing elbow and two small pieces of heater hose one 3/8 and the other 5/8.Theres not much room to work with bach there and the right part would have gone on easier,but everything fit tight and it's running great now.
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