Strange Running Diag...., Weak idle, backfire thru exhaust, backfire thru carb. |
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Strange Running Diag...., Weak idle, backfire thru exhaust, backfire thru carb. |
1972 914 2.0 |
Sep 28 2016, 06:12 PM
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#1
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Member Group: Members Posts: 74 Joined: 9-December 13 From: United States Member No.: 16,745 Region Association: MidAtlantic Region |
1972 914 with '74 2.0L
The Problem: Car is hard to start. It backfires through the carb on light accel. It backfires through exhaust on decel. And it idles very low and wants to die after stopping. Runs fantastic on wide open. The Facts: Weber 40IDFs (freshly rebuilt and tuned, ran great for about 500 miles) Freshly Rebuilt engine (ran fine for around 2000 miles) All new ignition system (distributor, plugs, points, wires) Newer Tarret Fuel Pump (front mounted) Rubber fuel lines from tank to engine (not OE) Checked the valves, they're fine. Questions: Could It be low fuel pressure, Degrading fuel lines, Timing issue, Vacuum leak.... I'm at a loss currently. Lets hear your thoughts and experiences. Thanks Chris |
Localboy808 |
Sep 29 2016, 10:02 AM
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#2
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Member Group: Members Posts: 185 Joined: 17-July 16 From: Palmdale, Ca Member No.: 20,194 Region Association: None |
1972 914 with '74 2.0L The Problem: Car is hard to start. It backfires through the carb on light accel. It backfires through exhaust on decel. And it idles very low and wants to die after stopping. Runs fantastic on wide open. The Facts: Weber 40IDFs (freshly rebuilt and tuned, ran great for about 500 miles) Freshly Rebuilt engine (ran fine for around 2000 miles) All new ignition system (distributor, plugs, points, wires) Newer Tarret Fuel Pump (front mounted) Rubber fuel lines from tank to engine (not OE) Checked the valves, they're fine. Questions: Could It be low fuel pressure, Degrading fuel lines, Timing issue, Vacuum leak.... I'm at a loss currently. Lets hear your thoughts and experiences. Thanks Chris Chris. Do you know if the carb linkage is opening both carbs at the same time equally and smoothly? Take a deep breath. Take it one step at at time. I've been there before. Trust me! New anything doesn't mean anything to me anymore. I recently installed new points and a condenser on my car and both went bad within 100 miles! If it were me I'd look at the linkage closely. If you know that's good. Check for good spark. I always carry extra points and condensers. Easy to swap them out just to test. Same thing with the coil. Once those are eliminated as possible suspects. Adjust the valves. Still problems? Maybe do a compression check. Still problems? Maybe blow out the idle circuits on the carbs? No fuel injection to diagnose so for me this would be easier. |
stugray |
Sep 29 2016, 10:05 AM
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#3
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Advanced Member Group: Members Posts: 3,825 Joined: 17-September 09 From: Longmont, CO Member No.: 10,819 Region Association: None |
"Vacuum leak..."
Hold it at slightly elevated idle (I use a popsicle stick behind the master carb lever) Take some engine cleaner or carb cleaner and spray it around the intake manifold bases (where they go into the heads), carb bases, and carb shafts. See if the engine bogs |
ChrisFoley |
Sep 29 2016, 03:00 PM
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#4
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I am Tangerine Racing Group: Members Posts: 7,935 Joined: 29-January 03 From: Bolton, CT Member No.: 209 Region Association: None |
It sounds like you have one or two plugged idle jets.
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