rough/ surging idle
Moderator
Joined: Jan 2001
Posts: 56,995
Likes: 2,741
From: Virginia
If you turn the distributor till the #1 mark comes up, and the distributor rotor is pointing to #1, turn the engine by hand one turn till the tdc mark comes up again. LIne it up to the mark. Pull the distributor cap, you will find the rotor is NOT pointing to #1 plug wire. Pull the distributor out, spin the guts of the distributor around by hand till the rotor is pointing to #1 plug wire, and then stab it back in place. You probably already know the routine of rotor moves a little as you stab it in place, and the oil pump might not engage. After fiddling with all that, the rotor should be pointing to #1 now.
See what happens. You most likely will have to give the dist a minor twist one way or the other to get it running. Then you can put a timing light on it and get it exactly right.
Lead Driver
Joined: Jul 2011
Posts: 8,679
Likes: 191
From: On the Edge of the Desert
Just stopping by to drop my quick tidbit.
I've been chasing a surging idle on my 86 EFI 5.0 for a couple of years and had basically given up on it. "that's just gonna be how she runs"
Last weekend I changed out the brake booster and not only are the brakes way better, but the surging idle has gone away. Obviously the booster was leaking vacuum.
I've been chasing a surging idle on my 86 EFI 5.0 for a couple of years and had basically given up on it. "that's just gonna be how she runs"
Last weekend I changed out the brake booster and not only are the brakes way better, but the surging idle has gone away. Obviously the booster was leaking vacuum.
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Cross-Country
Joined: Sep 2023
Posts: 94
Likes: 2
Final Update:
first, i want to give a thanks to you guys for guiding me in the troubleshooting process. as of now, i’ve got the timing set with the new HEI distributor and the new carb runs great. Any vacuum leaks it had on deviously are now gone, along with the EEC-IV wiring harness. The truck runs great and fires up no problem.
Again, thanks to all of you for your help.
first, i want to give a thanks to you guys for guiding me in the troubleshooting process. as of now, i’ve got the timing set with the new HEI distributor and the new carb runs great. Any vacuum leaks it had on deviously are now gone, along with the EEC-IV wiring harness. The truck runs great and fires up no problem.
Again, thanks to all of you for your help.
FTE Legend
Joined: Nov 2015
Posts: 30,935
Likes: 4,124
From: Angier, NC
Good to hear it is running like new again.
Anyone with a feed back system that is having issues as you found the fix is replace the carb, dist. and remove the computer & wiring.
Got a question, Have you opened up the computer to see if the caps are bad?
If they are bad they could be leaking / wet, brown or blown out of shape.
Dave ----
Anyone with a feed back system that is having issues as you found the fix is replace the carb, dist. and remove the computer & wiring.
Got a question, Have you opened up the computer to see if the caps are bad?
If they are bad they could be leaking / wet, brown or blown out of shape.
Dave ----
Thread Starter
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Cross-Country
Joined: Sep 2023
Posts: 94
Likes: 2
Good to hear it is running like new again.
Anyone with a feed back system that is having issues as you found the fix is replace the carb, dist. and remove the computer & wiring.
Got a question, Have you opened up the computer to see if the caps are bad?
If they are bad they could be leaking / wet, brown or blown out of shape.
Dave ----
Anyone with a feed back system that is having issues as you found the fix is replace the carb, dist. and remove the computer & wiring.
Got a question, Have you opened up the computer to see if the caps are bad?
If they are bad they could be leaking / wet, brown or blown out of shape.
Dave ----
Also, i know i said the truck runs fine and dandy, beside from two little things:
it will occasionally backfire (tiny backfire, almost like a burp) and will crank slow for a second and fire up. is my timing too advanced? retarded?
FTE Legend
Joined: Nov 2015
Posts: 30,935
Likes: 4,124
From: Angier, NC
The slow cranking could be to far advanced.
You did not say when either of them happen?
Saw cranking cold or hot starting?
You can pull the power wire to the distributor and see if it still happens if not I would think timing.
Hiccup or burp cold or hot?
When trying to start or hot running and taking off from a stop.
Dave ----
You did not say when either of them happen?
Saw cranking cold or hot starting?
You can pull the power wire to the distributor and see if it still happens if not I would think timing.
Hiccup or burp cold or hot?
When trying to start or hot running and taking off from a stop.
Dave ----
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Cross-Country
Joined: Sep 2023
Posts: 94
Likes: 2
The slow cranking could be to far advanced.
You did not say when either of them happen?
Saw cranking cold or hot starting?
You can pull the power wire to the distributor and see if it still happens if not I would think timing.
Hiccup or burp cold or hot?
When trying to start or hot running and taking off from a stop.
Dave ----
You did not say when either of them happen?
Saw cranking cold or hot starting?
You can pull the power wire to the distributor and see if it still happens if not I would think timing.
Hiccup or burp cold or hot?
When trying to start or hot running and taking off from a stop.
Dave ----
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mark alderson
FE & FT Big Block V8 (332, 352, 360, 390, 406, 410, 427, 428)
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Sep 2, 2005 09:17 AM
