rough running 302
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Senior User
Joined: Nov 2001
Posts: 196
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From: beverly, Ohio
rough running 302
[updated:LAST EDITED ON 26-Dec-01 AT 07:39 PM (EST)] I have an 85 f-250 that came factory with the 6.9 diesel. When it threw a rod I replaced it with a 302. Here's my problem' when the truck is at idle it does'nt run worth a crap, but when I push down on the brake pedal it runs like a top. At cold start it won't idle unless I push the brake pedal, then it idles like it should. It acts as if the carb is loading up and it starts to die, until I hit the brake.
please help!
scott
please help!
scott
Senior User
Joined: Feb 2001
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rough running 302
Wow! That's a good one! Just a guess, but if you have power brakes there's a vacuum booster involved. Maybe it's got a fat intake leak through the booster that you're inadvertently sealing off when you get on the brake?
Posting Guru
Joined: Jun 1999
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From: Durham
rough running 302
It definately sounds like a vacuum leak. Check your hoses, especially the large vacuum hose that goes to the power brake booster. You could also have a leak around the base of your carb (I assume you have a carburated engine??)
Senior User
Joined: Apr 2001
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rough running 302
I don't think diesels use engine vacum.You need a power brake boster off a carbed 250.If your state has smog tests you won't have to deal with it.You may want to check out entire brake system to see if you need differant brake parts also.
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Joined: Apr 2001
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rough running 302
YES! But you MUST only rely on a setup thats for a 302 now!You can go to a boneyard for the booster.Also I suggest you see if the rest of system is interchangable with a diesel setup.Call a parts store and find out if the proportioning valve,master cylinder is the same and so on.Get it right...don't mess around with brakes.
