86 f250 help
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86 f250 help
Hello I have an 86 f250 w. Previously I had taken off the smog pumps and I was just going to delete the entire system... But it was a lot bigger of a job I thought than just plugging s few vacuum lines. But anyway while I had the pumps and hoses off it started to backfire through the carburetor and I just finished putting all pumps and lines back on and the timing is still retarded and backfiring through the carb. Do you guys think I need a new timing advance?
FTE Legend
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From: Northeast, OK
You need to tell us a lot more. First, which engine? By saying "smog pumps" it must either be an 8600+ GVW w/a 351HO or a 460. Both run a Holley 4180C, and those are prone to backfiring on overrun due to a blown power valve.
But, backfiring under load can be an ignition problem.
So, when does yours backfire?
But, backfiring under load can be an ignition problem.
So, when does yours backfire?
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You need to tell us a lot more. First, which engine? By saying "smog pumps" it must either be an 8600+ GVW w/a 351HO or a 460. Both run a Holley 4180C, and those are prone to backfiring on overrun due to a blown power valve.
But, backfiring under load can be an ignition problem.
So, when does yours backfire?
But, backfiring under load can be an ignition problem.
So, when does yours backfire?
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It starts to backfire when I got on the throttle.
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FTE Legend
Joined: Jul 2010
Posts: 32,875
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From: Northeast, OK
My guess is that what you have is a vacuum leak as a very lean fuel/air mix can cause a miss or backfire. But, a poor spark can do it also.
So, let's describe both issues. You've been playing with the AIR pumps and probably the EGR valve and vacuum lines. And a significant vacuum leak can cause it to run poorly and miss or backfire. So, check all the vacuum lines to ensure they go somewhere and aren't open, and check them to see if they are cracked. Also check the carb-to-EGR plate gasket and the EGR plate-to-manifold gasket. Any leak of air into the manifold will cause the engine to run poorly.
And, a weak spark or bad plugs, wires, distributor cap, or rotor can cause it to miss under load - meaning heavy throttle. But, check out the vacuum lines and other things before we delve into the ignition.
So, let's describe both issues. You've been playing with the AIR pumps and probably the EGR valve and vacuum lines. And a significant vacuum leak can cause it to run poorly and miss or backfire. So, check all the vacuum lines to ensure they go somewhere and aren't open, and check them to see if they are cracked. Also check the carb-to-EGR plate gasket and the EGR plate-to-manifold gasket. Any leak of air into the manifold will cause the engine to run poorly.
And, a weak spark or bad plugs, wires, distributor cap, or rotor can cause it to miss under load - meaning heavy throttle. But, check out the vacuum lines and other things before we delve into the ignition.
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My guess is that what you have is a vacuum leak as a very lean fuel/air mix can cause a miss or backfire. But, a poor spark can do it also.
So, let's describe both issues. You've been playing with the AIR pumps and probably the EGR valve and vacuum lines. And a significant vacuum leak can cause it to run poorly and miss or backfire. So, check all the vacuum lines to ensure they go somewhere and aren't open, and check them to see if they are cracked. Also check the carb-to-EGR plate gasket and the EGR plate-to-manifold gasket. Any leak of air into the manifold will cause the engine to run poorly.
And, a weak spark or bad plugs, wires, distributor cap, or rotor can cause it to miss under load - meaning heavy throttle. But, check out the vacuum lines and other things before we delve into the ignition.
So, let's describe both issues. You've been playing with the AIR pumps and probably the EGR valve and vacuum lines. And a significant vacuum leak can cause it to run poorly and miss or backfire. So, check all the vacuum lines to ensure they go somewhere and aren't open, and check them to see if they are cracked. Also check the carb-to-EGR plate gasket and the EGR plate-to-manifold gasket. Any leak of air into the manifold will cause the engine to run poorly.
And, a weak spark or bad plugs, wires, distributor cap, or rotor can cause it to miss under load - meaning heavy throttle. But, check out the vacuum lines and other things before we delve into the ignition.
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Joined: Jul 2010
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From: Northeast, OK
If that is the problem. But, don't forget the EGR gaskets. And the EGR valve itself can have a blown diaphram. You can test for that by pulling the vacuum line to the valve and plugging the line. Same thing for the brake booster, and the cruise control if you have it. Anything that is hooked up to vacuum can fail and admit air. A little bit here and a little bit there and the engine is so lean it can't run right. Fix all of the problems and it'll run right.
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If that is the problem. But, don't forget the EGR gaskets. And the EGR valve itself can have a blown diaphram. You can test for that by pulling the vacuum line to the valve and plugging the line. Same thing for the brake booster, and the cruise control if you have it. Anything that is hooked up to vacuum can fail and admit air. A little bit here and a little bit there and the engine is so lean it can't run right. Fix all of the problems and it'll run right.
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