igniton module
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Postmaster
Joined: Jul 2003
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From: iowa
igniton module
Can a weak ignition module cause my 1979 f150 to run sluggish?
Ok, my 390 has been real sluggish on the bottom end last month or so. It started after i switched metering rods in my edelbrock 600. I put the old ones back in and changed the plugs but it is still sluggish. It seems bogged down but the carb is tuned. I guarantee its not running rich. It seems to be sluggish from idle to 2000 rpm. I have my timing at 12 btdc and 40 total. i have checked the engine vaccum and had 18. And i had 20 on vaccum advance. I have tryed my new Holley and the same thing happens. The dizzy and ignition module are less then a year old. The ignition module was some cheap brand piece. I want to believe its a timing thing but i am not sure what in specific is the cause. I have some dizzy springs for earlier advance but i didn't have the problem before so i have not used them. Tryed a new coil and that didn't help. I think its down to the module or dizzy.
Any suggestions?
Ok, my 390 has been real sluggish on the bottom end last month or so. It started after i switched metering rods in my edelbrock 600. I put the old ones back in and changed the plugs but it is still sluggish. It seems bogged down but the carb is tuned. I guarantee its not running rich. It seems to be sluggish from idle to 2000 rpm. I have my timing at 12 btdc and 40 total. i have checked the engine vaccum and had 18. And i had 20 on vaccum advance. I have tryed my new Holley and the same thing happens. The dizzy and ignition module are less then a year old. The ignition module was some cheap brand piece. I want to believe its a timing thing but i am not sure what in specific is the cause. I have some dizzy springs for earlier advance but i didn't have the problem before so i have not used them. Tryed a new coil and that didn't help. I think its down to the module or dizzy.
Any suggestions?
Last edited by fordeverpower; May 3, 2004 at 09:02 PM.
Senior User
Joined: Jan 2003
Posts: 176
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From: Addison,Texas
You've got 20" Hg. at the advance at idle? (With 18 at the manifold?) If you've got the advance tied to manifold vac and your primary advance isn't mechanical than opening your throttle plates is going to drop your advance way back.
It would certainly bog then.
If the box was malfunctioning it would tend to sputter and miss throughout the range and it would probably get worse the higher the RPM.
ash
['The Motorcraft ones are better.']
It would certainly bog then.
If the box was malfunctioning it would tend to sputter and miss throughout the range and it would probably get worse the higher the RPM.
ash
['The Motorcraft ones are better.']
Posting Legend
Joined: Sep 2001
Posts: 30,255
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Now you have a spare... Are you way out in the boonies or something? Around KC all of the major chain parts stores have test equipment. There is an entire test process listed in most repair manuals for the ignition system. Try running thru it.
Lead Driver
Joined: Nov 2000
Posts: 6,635
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From: Albuquerque
I'm with Marty, if you are on ported vacuum your advance wont come in as fast. At least untill you mash on it a bit.
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Posting Legend
Joined: Sep 2001
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When the engine is cold the thermostatic vacuum swicth applies manifold vacuum to the distributor. As soon as it warms up it applies ported (venturi) vacuum for normal running. If the engine overheats it applies manifold vacuum to the distributor.
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From: iowa
i run ported vaccum but never have had the problem quite as bad before. I tryed manifold but didn't get the results i wanted. I might use use crane advance springs to bring the timing in quicker!