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1967 - 1972 F-100 & Larger F-Series Trucks Discuss the Bumpsides Ford Truck

Idle Very Rough

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Old Oct 24, 2005 | 04:35 PM
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Idle Very Rough

I just bought a 1968 F-100 with a 390 and while it is idling, it is very rough and out the drivers side exhaust, it will pop but it's not consistent. It is idling at around 500 rpm's. It has been setting up for about 5 months and yesterday was the first time it has been driven since. Any suggestions on what the many problems I have. I have already sprayed the carb with carb cleaner and it has not made any difference yet. Any suggestions will be appreciated.
 

Last edited by who243; Oct 24, 2005 at 04:48 PM.
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Old Oct 24, 2005 | 04:46 PM
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Welcome to the forum, For now recheck the engine firing order and recheck your timing.
 
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Old Oct 24, 2005 | 06:42 PM
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Check your vacum lines as well I had one with a miss at idle and it was the power brake booster leaking
 
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Old Oct 25, 2005 | 11:20 AM
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rebuild the carb, or buy a new one if its easier for you. They are right though, check your basics first (timing, vacume, plugs), most likly though your idle passages in the carb are gunked up causing half the 8 cylinders to be lean. How does it run when driving?
 
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Old Oct 25, 2005 | 11:34 AM
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Idling at 500 rpms is a little low, I'd bring that up to about 700-800 rpms. Then check what the other posts a saying.
 
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Old Oct 25, 2005 | 06:39 PM
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Definetly take a peek at the plugs, just to get an idea of whats firing.
 
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Old Oct 28, 2005 | 09:10 PM
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I checked all the vacume lines and they are fine. I got it idling at about 600 rpms and it still backfires out both exhaust pipes but not like before.It also has a little black smoke from each exhaust so I'm sure the the carb needs some fine tuning.I have taken the carb off and am going to clean it out.The carb was just put on it before it was parked.As soon as I get some pics I will post them. Thanks for all the help.
 
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Old Oct 28, 2005 | 09:18 PM
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It may be worth doing a compression check also. Get an idea of internal condition. Especially if the exhaust mainfolds are leaking at the heads. Good Luck
 
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Old Oct 28, 2005 | 09:26 PM
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your timing and fuel ratio are way out of wack. time it to 12 btdc with vacuum advance unhooked. hook up a vacuum gauge and tune the carb.
 
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Old Oct 28, 2005 | 09:36 PM
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I'd start with a full tune-up. Points, condensor, plugs, cap and rotor, timing, air filter, maybe even plug wires. After thats done and a few tanks of gas were through it , then I'd look at the carb.
Back in the '60's a tune up every 8-10,000 miles was the norm.

I just got my '70 out for the first time since May and it was running rough too.....turned out to be a loose spark plug wire.
.
 
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Old Oct 28, 2005 | 09:44 PM
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Gashog, Where are you hooking the vacuum gauge, and what do you look for? thanks
 
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Old Oct 29, 2005 | 07:26 PM
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I cleaned the carb this morning and put it back on and it runs great. I also checked the plugs,wires and put a timing light to it and set it to 12 btdc.Thanks for everyone's help.
 
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Old Oct 31, 2005 | 09:59 AM
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Recheck the spark plugs and check if they are black and carboned. Replace if necessary.
 
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