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#1
06-17-2002, 10:42 PM
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Intermitent Stumble at all speeds
The 72 280se 4.5 is at it again, it stumbles about five minutes out and will also cut out at idle at between 30 sec. to a few minutes apart. It will accelerate without incident and then go back to its behavior once cruising speed is achieved. Can it be the fuel filter or pump? The ignition system should not be culprit as most of the components are fairly new and the injector points were replaced with a like new used set. Vacuum leak? I'm open to suggestions. It doesn't seem to affect driveability but I'm paranoid about breaking down again.
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#2
06-18-2002, 02:30 PM
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Rather than guess, find a shop with a dynamometer so that you can test it sitting still at highway speeds and conditions.
Armed with a fuel pressure gauge, Ignition scope and maybe a dwell meter to watch the fuel injectors, you'll know exactly whats wrong in about 30 minutes. -CTH
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#3
06-18-2002, 11:55 PM
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Dynometer? We've heard of them out here in Kansas, you know in magazines and such. There might still be one down at Pittsburg State College but .... O.K. engine scope.. don't have. Fuel pressure gauge.. its on my list. Dwell meter , I got. How do you diagnose injectors with it? With an XR-700 and MSD 6AL would the dwell be relevant?
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#4
06-19-2002, 07:33 AM
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A dwell meter just shows you that a circuit is oscillating and at what percentage of its life it's "ON" vs "OFF" (a duty cycle). The injectors receive a chain of pulses that can be measured that way.
I've been to Kansas (well, only once), somebody there has to have both a dynamometer and an engine scope. Ask the nearest mechanic. -CTH
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#5
06-19-2002, 09:03 PM
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Well the dwell meter was hooked up in the standard test configuration and .... nothing, no dwell, no rpms, nada. On cars with electronic ignitions it says to refer to the manual. But mine is aftermarket and has no tach hook up. So I went hunting vacuum leaks with carb cleaner and there seems to be leakage around some of the injectors. New seals seem to be in order, could this be the cause of the miss?
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#6
06-19-2002, 09:13 PM
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Leaking around the injectors will definitely mess you up. There are TWO seals on each injector. There's the big rubber ring you can see and small plastic tip that you don't see w/o first removing the injector.
If you were using the dwell meter on the ignition system, there is a trick to hooking it up. You don't connect it to the coil. Instead, follow the green wire from the distributor down to a connector block. Clip the dwell meter lead to that block too. -CTH
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