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Oct 5, 2023 | 11:57 AM

kats28911

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5th Gear

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kats28911

Have a 1985 F-250 with a 460 and 4 speed having problems with it not wanting to go over 25mph any thoughts?

Oct 5, 2023 | 12:22 PM

BigBlue2

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If the engine starts and idles normally but can't build RPM you could have a fuel supply issue. Replace any fuel filters. Check your fuel pump pressure and flow. If timing and fuel check out you could have a plugged exhaust.

Oct 5, 2023 | 01:21 PM

kenny nunez

Cargo Master

Joined: Oct 2011

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From: Kenner,La.

25 mph 460

Another possible could be a plugged up exhaust system.

Oct 5, 2023 | 02:04 PM

kats28911

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5th Gear

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Thanks yes it idles ok and the exhaust sounds great Have replaced the fuel pump on rear tank cant find any other leaks

Oct 5, 2023 | 03:03 PM

kr98664

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What are the symptoms? Does the engine chug? Or just bog down? What happens at the same RPM in 3rd gear?

Oct 5, 2023 | 03:11 PM

FuzzFace2

FTE Legend

Joined: Nov 2015

Posts: 30,876

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From: Angier, NC

I am for a plugged exh.
If running a cat it could vary well be plugged at this time.

Also dont over look a bad muffler.
The baffles may have come loose and is plugging the path for the gasses to get out.
When cold take a rubber or dead blow hammer and hit the bottom of the muffler.
If you hear it rattle this it could be bad.

If you use a vacuum gauge on the motor what dose it read at idle and at higher RPM?
Same with a load on the motor what dose it read?
Or you could drop the exh before the cat and go for a test drive.
Dave ----

Oct 5, 2023 | 03:13 PM

BigBlue2

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Quote:

Originally Posted by kr98664

What are the symptoms? Does the engine chug? Or just bog down? What happens at the same RPM in 3rd gear?

Yes, and what is the history of the issue? All of a sudden or worse over time?

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Oct 5, 2023 | 03:18 PM

BigBlue2

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Joined: Apr 2002

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Quote:

Originally Posted by kats28911

Thanks yes it idles ok and the exhaust sounds great Have replaced the fuel pump on rear tank cant find any other leaks

A plugged exhaust limited situation the exhaust sounds good up to the point of too much back pressure. Happens pretty consistently at the same RPM and load.