 Troubleshooting question, Hot idle '73 2.0 too high |
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| Last930 |
 May 9 2015, 08:16 PM
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#1
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Member  Group: Members Posts: 60 Joined: 15-September 14 From: Illinois Member No.: 17,905 Region Association: Upper MidWest  |
My '73 2.0 idles beautifully when cold - right at 950-1,000 rpm. Once hot however it idles way to fast - around 2,000-2500 rpm. It runs great other than that. Any suggestions on troubleshooting?
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| r_towle |
May 9 2015, 08:22 PM
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#2
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Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States 
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Clean your distributor advance plates.
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| brant |
May 9 2015, 08:24 PM
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#3
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914 Wizard Group: Members Posts: 11,622 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains 
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As a test. Unplug one of the large decel valve hoses. Cap it with your finger and see if your decel is bad
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| toon1 |
May 9 2015, 08:28 PM
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#4
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Senior Member Group: Members Posts: 1,849 Joined: 29-October 05 From: tracy,ca Member No.: 5,022 |
It could be the dizzy( as mentioned)
. It can also be an air leak. Usually the air leak comes from the phenolic spacer between the intake runners and the head. The way you check is to let the car cool, fire it up and spray carb. Cleaner in that area. If the idle rises after you spray, thats where your leak is. Spray sparingly so you dont saturate the area . More than likely the spacer is cracked or the gaskets need to be replaced. Easy job. |
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| r_towle |
May 9 2015, 08:31 PM
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#5
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Custom Member Group: Members Posts: 24,574 Joined: 9-January 03 From: Taxachusetts Member No.: 124 Region Association: North East States
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It idles high when hot.....
Air leaks hot and cold.... |
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| brant |
May 9 2015, 08:44 PM
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#6
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914 Wizard Group: Members Posts: 11,622 Joined: 30-December 02 From: Colorado Member No.: 47 Region Association: Rocky Mountains
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QUOTE(r_towle @ May 9 2015, 08:31 PM)  It idles high when hot..... Air leaks hot and cold.... Last month on my road trip. My decel failed like this. It worked when cold and even for 20 miles. But hot highway driving caused a high idle after 30 minutes. Rust, diaphragm, heat... |
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| Last930 |
May 9 2015, 09:24 PM
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#7
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Member Group: Members Posts: 60 Joined: 15-September 14 From: Illinois Member No.: 17,905 Region Association: Upper MidWest |
QUOTE(r_towle @ May 9 2015, 09:22 PM) Clean your distributor advance plates. Distributor was just out ; everything is in good shape there. I'll try testing the decel valve tomorrow. |
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| boxsterfan |
May 9 2015, 11:15 PM
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#8
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914's are kewl Group: Members Posts: 1,776 Joined: 6-June 03 From: San Ramon, CA Member No.: 791 Region Association: Northern California |
Auxilliary Air Regulator sounds stuck open. That also sounds like too low of an idle for a cold start.
Just unplug the AAR hose from the intake plenum and block off the hose with your thumb. If the idle drops, you need a new AAR. They don't make them new anymore, but you can find a good used one here. |
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| Last930 |
May 10 2015, 07:44 AM
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#9
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Member Group: Members Posts: 60 Joined: 15-September 14 From: Illinois Member No.: 17,905 Region Association: Upper MidWest |
QUOTE(boxsterfan @ May 10 2015, 12:15 AM) Auxilliary Air Regulator sounds stuck open. That also sounds like too low of an idle for a cold start. Just unplug the AAR hose from the intake plenum and block off the hose with your thumb. If the idle drops, you need a new AAR. They don't make them new anymore, but you can find a good used one here. Can someone direct me to a picture of these parts? My manual doesn't have a clear photo of the decel and aar. Thanks, Dave |
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| somd914 |
May 10 2015, 08:00 AM
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#10
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Member Group: Members Posts: 1,171 Joined: 21-February 11 From: Southern Maryland Member No.: 12,741 Region Association: MidAtlantic Region |
Decel valve is on passengers side near the Manifold Pressure Sensor (MPS) towards the wheel arch
 AAR is on front side of intake plenum more towards driver's side   Not my photos BTW... |
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| Last930 |
May 10 2015, 08:48 PM
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#11
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Member Group: Members Posts: 60 Joined: 15-September 14 From: Illinois Member No.: 17,905 Region Association: Upper MidWest |
Warmed the car up well and took it for a 10-15 mile ride; by the time I got home it was idling perfectly stable at 900-1000 rpm. Intermittent glitches like this drive me nuts; I guess I'll drive it as is until the problem crops up continually.
Thanks for all the knowledge and suggestions! |
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