Slight surge at idle
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Senior User
Joined: Sep 2003
Posts: 133
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From: Colorado Springs
Slight surge at idle
After my truck is warmed up and idleing, it will surge slighty for a few seconds, then slow back down. It also seems to be sucking a lot of air. The air part I can understand because of the filter element I have right now. Could a vacume leak cause the surgeing? There is no EGR, the only vacume lines going to the carb are the PVC and advance. The manafold does have a vacume "tree" but all the opening are pluged as far as I can tell. The Truck runs good, but I know this surging is not right. 
New User
Joined: Feb 2004
Posts: 22
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From: Moorhead, MN
If all the ports are pluged on the vacume tree and the carb has a pcv and timing advance, where is the brake booster vac. line hooked too?????????? sounds like a vac. leak or high elevation jets in the carb
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Joined: Aug 2000
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Rew,
Before you spend time, effort, and money replacing stuff take a can of carb cleaner and spray it, while the engine is running of course, along the base of the carb, the throttle shafts, the union of the intake manifold to the head, around the vacuum tree, along vacuum hoses, and any where else that a vacuum leak could possibly occur. If you come across a leak you will hear the idle speed change. Keep spraying on that spot until you know exactly where it is leaking. If you have an air leak it could be as simple as intake manifold bolts needing to be retorqued or similarly the carb hold down nuts/bolts.
Good luck,
Mark
Before you spend time, effort, and money replacing stuff take a can of carb cleaner and spray it, while the engine is running of course, along the base of the carb, the throttle shafts, the union of the intake manifold to the head, around the vacuum tree, along vacuum hoses, and any where else that a vacuum leak could possibly occur. If you come across a leak you will hear the idle speed change. Keep spraying on that spot until you know exactly where it is leaking. If you have an air leak it could be as simple as intake manifold bolts needing to be retorqued or similarly the carb hold down nuts/bolts.
Good luck,
Mark
Thread Starter
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Senior User
Joined: Sep 2003
Posts: 133
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From: Colorado Springs
Mchild, I'll try that. But as of this morning, I had to pull the passanger side header to get the starter out. I thought I had a timing problem, turns out the starter was dieing. Ahh well
New User
Joined: Feb 2004
Posts: 5
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From: West Virginia
Rew,
I was having somewhat of the same problem and did not realize that my carb had loosened up. I had to take it off of the intake manifold, turn it over and tighten up the 4 crews holding the two pieces together. Incidentally, I cleaned the screws and used some clear fingernail polish as a mild form of locktite before putting back together to help prevent it from coming loose in the near future.
It helped smooth the idle out quite a bit. (Obviously, Ha!)
______________________________
1985 F150 4x4 300 I6 (ALL MINE!)
1990 Subaroooo (Little Ladies ride)
I was having somewhat of the same problem and did not realize that my carb had loosened up. I had to take it off of the intake manifold, turn it over and tighten up the 4 crews holding the two pieces together. Incidentally, I cleaned the screws and used some clear fingernail polish as a mild form of locktite before putting back together to help prevent it from coming loose in the near future.
It helped smooth the idle out quite a bit. (Obviously, Ha!)
______________________________
1985 F150 4x4 300 I6 (ALL MINE!)
1990 Subaroooo (Little Ladies ride)
