Oil change
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5th Wheeling
Joined: Aug 2022
Posts: 25
Likes: 1
From: Southeast Louisiana
Oil change
I have a 78’ f150 351m I just changed my oil and filter I run 20w50 . Now I’m getting a rough acceleration and rough idle I’m very confused as this has never happened before on an oil change. Any advice would be greatly appreciated,
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5th Wheeling
Joined: Aug 2022
Posts: 25
Likes: 1
From: Southeast Louisiana
No sir .. didn’t waste any oil on the ignition wires I’m just confused and also after I changed it my oil pressure gauge is no longer working anymore
someone did tell me that I may need to change the plug on the very back of the engine because it may be stopped up and cause a lot of back pressure. I just don’t know what it’s called for to order it
someone did tell me that I may need to change the plug on the very back of the engine because it may be stopped up and cause a lot of back pressure. I just don’t know what it’s called for to order it
Hotshot
Joined: Feb 2004
Posts: 10,785
Likes: 2,595
From: The Shenandoah Valley
Only plug on the back of the engine is a threaded in galley plug, there are two and they don't get changed, they have nothing to do with oil pressure. Behind the intake manifold is a sending unit, but it doesn't control oil pressure either, just generates a signal to the gauge inside the truck ... unless someone put a different gauge on it that uses a tube and the tube got broke / cut and oil is running out back there.
Any strange noises?
You didn't knock a vacuum hose loose, like the one to power brake booster, or forget to put the PCV valve in place connected to it's hose?
There are many causes of rough running, but here without more just shooting in the dark.
Any strange noises?
You didn't knock a vacuum hose loose, like the one to power brake booster, or forget to put the PCV valve in place connected to it's hose?
There are many causes of rough running, but here without more just shooting in the dark.
Fleet Mechanic
Joined: Mar 2013
Posts: 1,661
Likes: 1,062
From: Montana
Did you confirm proper level of oil with dipstick or just dump 5 quarts in? Reason I ask, if you poured the amount of oil in that you know goes in there, and didn't check the dipstick to confirm, I am wondering if the drain holes in the head are plugged or slow draining and you had a lot of oil inside the valve cover, enough that it was sucked into the carb through the PCV/breather when you started it up?
I really can't think of another reason for rough running other than what was already mentioned regarding knocking a plug wire or vacuum line loose.
I really can't think of another reason for rough running other than what was already mentioned regarding knocking a plug wire or vacuum line loose.
Fleet Mechanic
Joined: Mar 2013
Posts: 1,661
Likes: 1,062
From: Montana
Sorry for another stupid question, you did put the drain plug back in right? If you poured oil in and it just poured out the drain, no oil in the engine would certainly cause it to run rough and you wouldn't have any oil pressure either.
Logistics Pro
Joined: Jun 2004
Posts: 4,758
Likes: 3,372
From: South Central Utah
I would have to think the misfire is just a coincidence.
I'd pull your spark plugs and take a look at them.
I'd pull your spark plugs and take a look at them.
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More Turbo
Joined: Mar 2022
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Check for a vacuum leak. This happened to me once after an oil change in another vehicle. I didn't see the vacuum leak until I removed the air cleaner unit and saw the disconnected hose.
The oil pressure sender is on the back of the block, right in the middle behind the intake. You might have knocked the wire off the sender while doing something. My sender wire is just a push on fitting.
The oil pressure sender is on the back of the block, right in the middle behind the intake. You might have knocked the wire off the sender while doing something. My sender wire is just a push on fitting.
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Fleet Mechanic
Joined: Dec 2007
Posts: 1,504
Likes: 339
From: Wildwood Pa
I installed my rebuild original alternator a few months back, & had the same rough running problem you did. Turns out one of the 45 year old vacuum lines was disturbed while doing the R & R on the alternator & developed a crack. Replacement solved my problem.
More Turbo
Joined: Apr 2007
Posts: 615
Likes: 93
The new clean oil may have loosened up sum sludge that ended up in a lifter.
I had an 80's Ford van that I changed oil in and hit the interstate. The sludge that came loose clogged the oil pick up screen and lack of oil wiped the bearings. Knocked all the way home.
I had an 80's Ford van that I changed oil in and hit the interstate. The sludge that came loose clogged the oil pick up screen and lack of oil wiped the bearings. Knocked all the way home.
Mountain Pass
Joined: Oct 2023
Posts: 163
Likes: 59
From: Kaslo, BC, Canada
Daniel N - What brand of oil filter did you install? If it was a Fram I suggest that you immediately replace it with a Wix filter. I have seen issues with Fram filters where they literally come unglued internally and plug off the flow of oil. If you did not install a Fram but some other brand you may still want to install a Wix.
If you do install a Wix take a moment and cut open what you removed to see if it is still intact internally.
If you do install a Wix take a moment and cut open what you removed to see if it is still intact internally.
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