falling flat 89 460
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Joined: Apr 2003
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falling flat 89 460
Im working on a 89 460 that runs fine untill about 2800rpm and then it fall flat and missfires and get real sluggish even if i push the cluth in it wont stop missing until i let off th acc pedal then it fine until i go over 2800 rpm again.
wayne
wayne
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
When was the last tune up performed?
Have you checked for codes?
Could be catalytic converter plugged...ahh but that's an assumption without more info on the truck, like headers, no cats, etc. Give us more info on the engine and anything modified from the factory.
Have you checked for codes?
Could be catalytic converter plugged...ahh but that's an assumption without more info on the truck, like headers, no cats, etc. Give us more info on the engine and anything modified from the factory.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Check fuel pressure at idle, you should see 32-35psi and when vacuum line is removed from the regulator you should see 39-45psi. If pressure is low or drops below the idle measurement at any time the fuel filter is clogged, one of the pumps is failing, or the selector valve is failing.
Logistics Pro
Joined: Jul 2009
Posts: 3,635
Likes: 3
From: Lansdale, PA
I'm going to suggest a combination of both previous replies.
Give it a full tuneup, with fuel filter, air filter, pcv valve, o2 sensor, plugs wires cap rotor, and run a can of seafoam in the fuel.
Check fuel pressure, and check for stored codes.
Fleet Mechanic
Joined: Feb 2007
Posts: 1,652
Likes: 79
From: Mooresville, NC
Fuel pressure is a leading culprit.
(Probably best to rule out fuel pressure first.....).........89 had that quirky out of tank high pressure pump with the dual selector valve........in 90 the 460's went with in-tank pumps........
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