460 issues
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460 issues
ive got a 1990 F-250 with a fuel injected 460 and a 5 speed, had been running rough at an idle until i changed the iac valve, now i have a bad skip, tryed changing spark plugs, didnt help any, checked the compression on the trouble cylinder and number 7 has none, any suggestions would be wonderful
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Joined: Aug 2006
Posts: 5,670
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From: Sand Lake, MI
None as in zero zip nada?
Problem come on suddenly? as in was running good hitting on all eight one minute severe miss the next?
Or started as light almost unnoticeable miss/stumble? then noticed blowing little oil with it both conditions became more noticeable/severe over period of time?
Take the valve cover off turn the engine over make sure the valves are opening and closing that cylinder. Both rockers are fully intact, not cracked/broke or bent. Spin both push rods with fingers watching them rotate (do so both valves fully closed position so you can spin them fairly easy) verify neither is bent.
If find everything there looks good....... dump a tablespoon full worth of engine oil down the plug hole, immediately retest compression. See if has any effect on compression reading, it'll need work regardless by that point but be little more info to go on going in.
Problem come on suddenly? as in was running good hitting on all eight one minute severe miss the next?
Or started as light almost unnoticeable miss/stumble? then noticed blowing little oil with it both conditions became more noticeable/severe over period of time?
Take the valve cover off turn the engine over make sure the valves are opening and closing that cylinder. Both rockers are fully intact, not cracked/broke or bent. Spin both push rods with fingers watching them rotate (do so both valves fully closed position so you can spin them fairly easy) verify neither is bent.
If find everything there looks good....... dump a tablespoon full worth of engine oil down the plug hole, immediately retest compression. See if has any effect on compression reading, it'll need work regardless by that point but be little more info to go on going in.
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Just came on suddenly, that's why I thought it fouled a plug again, it likes to eat them. Was fine one day. Ran great then the next day I put gas in it and got about a half mile up the road and it started. Pulled the cover off and every thing is fine. Rockers are both intact no bent push tubes. And I have good power goin through the wire.
Lead Driver
Joined: Aug 2006
Posts: 5,670
Likes: 12
From: Sand Lake, MI
Just came on suddenly, that's why I thought it fouled a plug again, it likes to eat them. Was fine one day. Ran great then the next day I put gas in it and got about a half mile up the road and it started. Pulled the cover off and every thing is fine. Rockers are both intact no bent push tubes. And I have good power goin through the wire.
Put little bit of oil down the plug hole test it see if the compression in that cylinder rises substantially, or just a little bit.
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ill give the oil trick a try, honestly i forgot about that trick, but it was a sudden thing, i had run it all day the day before, and was fine, but i will try that and see if it does anything, im thinkin it might have a hole in the piston tho, but yes either way it needs help, i was actually thinkin about dropping in the undesired 6.0 diesel, but havent found anyone that has done that swap yet
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