Bad day for the 914 |
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Bad day for the 914 |
57lincolnman |
Jul 9 2015, 02:10 PM
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#1
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Member Group: Members Posts: 174 Joined: 14-September 10 From: Los Angeles Member No.: 12,175 Region Association: Southern California |
Prior symptoms which progressively worsened: at full engine operating temperature (200 degrees) the idle becomes somewhat erratic at a stoplight. When I pull away in first gear, it would "stumble" or hesitate and then take-off. This would only happen after the car had been driven for about 45 min - 1 hr. Prior to that the car would operate fine.
Today: the symptoms progressed to complete failure. After driving for about an hour, the car had a very weak idle. When I gave it gas to steady out the idle it backfired twice. It progressed with practically no engine power and then finally died in the middle of intersection (of course!). There was an immediate smell of raw gas. Now it will turn over but won't fire. The car was towed to the shop. I was afraid of an engine fire so towing seemed the most prudent thing to do. Background: it has a Mallory electronic ignition with stock coil and correct spark plug wires, we've tested for vacuum leaks and there aren't any. The air flow meter was replaced with a rebuilt unit about 1 year ago (this could be the culprit). After the backfire it will certainly need to be replaced... again. The throttle body control valve unit was also replaced about two years ago. The cylinder head temp sensor unit is seated properly and tests OK. Any suggestions of where to look next are greatly appreciated. Thanks. |
JawjaPorsche |
Jul 9 2015, 02:23 PM
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#2
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Advanced Member Group: Members Posts: 3,463 Joined: 23-July 11 From: Clayton, Georgia Member No.: 13,351 Region Association: South East States |
What year, what engine? Fuel pump?
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57lincolnman |
Jul 9 2015, 03:20 PM
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#3
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Member Group: Members Posts: 174 Joined: 14-September 10 From: Los Angeles Member No.: 12,175 Region Association: Southern California |
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davep |
Jul 9 2015, 03:31 PM
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#4
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914 Historian Group: Benefactors Posts: 5,151 Joined: 13-October 03 From: Burford, ON, N0E 1A0 Member No.: 1,244 Region Association: Canada |
If it was not for the smell of raw gas I would think it was starved for fuel; possibly dirty filter, dirty sock in tank, or plugged vent creating a vacuum in the tank. Something that gradually builds up over time.
The other possibility is some ignition component overheating causing a gradually weakening spark. These items can be checked, but you need to be prepared to do a test while the failure mode is present. |
Jeffs9146 |
Jul 9 2015, 03:36 PM
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#5
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Ski Bum Group: Members Posts: 4,062 Joined: 10-January 03 From: Discovery Bay, Ca Member No.: 128 |
Vacuum line/intake progressively cracking until total fail!
Vacuum hoses: Hoses should be replaced every 5 years. They lose elasticity when fitted, hardening and eventually cracking. Replace the entire set with a new set. Manifold Pressure Sensor: Cracked diaphragm, leaky case. Injector seals: Leaks due to hardening and cracking. Intake manifold gaskets: Cracked, poorly sealed and/or torqued. Intake runner boots: Leaks due to hardening and cracking. Intake manifold (plenum): Can have leaks due to seam cracks and cracks around other fittings. Cold start valve: Leaks from the valve itself and the seal to the plenum. Throttle body seal: Missing or cracked gasket to the plenum. Throttle body shaft: Worn shaft leaks air past the throttle plate. Auxiliary air regulator: Stuck open, defective valve Deceleration valve: Stuck open, or leak in the control diaphragm Distributor advance/retard: Either or both the advance and retard diaphragms cracked or leaky PCV Valve: Stuck open or worn out. |
JawjaPorsche |
Jul 9 2015, 03:52 PM
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#6
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Advanced Member Group: Members Posts: 3,463 Joined: 23-July 11 From: Clayton, Georgia Member No.: 13,351 Region Association: South East States |
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Mueller |
Jul 9 2015, 04:01 PM
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#7
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914 Freak! Group: Members Posts: 17,146 Joined: 4-January 03 From: Antioch, CA Member No.: 87 Region Association: None |
What year, what engine? Fuel pump? Sorry, 75' 1.8L, stock fuel injection. Could be the fuel pump. But a backfire? Pump in front on 75 so probably not pump. 1.8 hates vacuum leaks. Yep, even the o-ring for the oil fill cap can be suspect. When I had my last 1.8 I took all the hoses that it didn't need that went to the elbow and machined some delrin plugs and i will do the same for my 1.7 that I will be putting L-Jet on. For spark I used a Mallory Unilite which I'd love to have again...which due to current prices won't happen! Wow they are expensive now! |
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