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Discussion Starter · #1 ·
I am looking at buying a1985 f350 6.9idi. Supposedly it has 79,000 miles and the seller is selling it very cheap (under $2000). It has a rough idle but seller doesn't know what wrong with it. The fuel injectors have been serviced but that all. What could be causing the rough idle and am I looking at a long of money to fix. The truck has "normal" puff of smoke at start up and normal smoke drink acceleration. I am new to diesel so any help would be great! Thanks
 

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Welcome to the Diesel Stop.

What "service" was done to the injectors and how long (miles) ago? With only 79,000 miles on the engine I wouldn't think puffs of smoke are normal.
 

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You can bet that 85 has more than 79K miles on it in 30 years. The five digit odometer can roll over many times. More then likely 279K or even 379K. JMO.
 

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Discussion Starter · #7 ·
I'm just worried about a seized piston or something major. Also the 79,000 miles was a bit concerning/suspicious for an old truck. Nice truck though. Is there a way to tell in a piston is seized?
 

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A seized piston wouldn't let the engine turn over.
 

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Hi. Rough idle is minor. Probably air related, these trucks are bare bones and easy to fiqure out.
How can you say it's minor by staring at a computer screen? It could be burned valves, flat cam lobes or a number of other things costing way more in repairs than the truck is worth.


"........ and normal smoke during acceleration"
Actually you shouldn't see any smoke during acceleration. Brown/black smoke would mean excess fueling, blue smoke generally means a worn out engine, bad rings, scored cylinder walls, etc.
 
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