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1985 buick lesabre, thunking sound and power loss

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New User

Feb 26, 2013, 12:53 AM

Post #1 of 3 (1055 views)
1985 buick lesabre, thunking sound and power loss Sign In

1985 buick lesabre
8 cylinder,

This winter my car has been experiencing multiple issues.
Vehicle starts well enough, but has an erratic idle and threatens to die if I do not accelerate until it warms a bit. Black smoke plus smell of gas when i do this but the black smoke and gas smell go away after the engine starts to warm up. I have been dealing with this issue all winter, been unable to fix it due to poverty.
But now something new is happening.
Today after getting off of work I went through the standard start up procedure I encountered a serious problem. Now when I accelerate I hear and feel a loud thunking noise from the engine. This thunking noise occurs only when I hit the accelerator, while coasting at various speeds it is silent. There is a loss of power when this occurs and it is really bad if I try to go up any hills or try to accelerate quickly (especially from a standstill). The power loss can kill the engine and I had it die at an intersection (after waiting for the light to change to green, I hit the gas, heard the thunking, got into the intersection, then engine died, placed it in park restarted car and limped it through the intersection.) I can get the engine to make the noise when I am in park. If I rev it hard in park I can hear the noise but it is muffled and weak.

(This post was edited by akasa on Feb 26, 2013, 12:59 AM)

jamie lindgren
New User

Feb 26, 2013, 1:51 AM

Post #2 of 3 (1033 views)
Re: 1985 buick lesabre, thunking sound and power loss Sign In

My thought is the problem is internal, the black smoke is due to more than enough fuel in the intake (sticky injector, bad o2, bad egr ex..). When the car is cold everything has its full amount of clearance play but once it is warmed up everything expands and swells causing the noise to go away. Start by looking at the o2 sensor and catalytic converter. This may be more than one problem going on.

New User

Feb 26, 2013, 3:20 AM

Post #3 of 3 (1026 views)
Re: 1985 buick lesabre, thunking sound and power loss Sign In

The noise does not go away when it warms up. The black smoke and erratic idling go away when it warms up. The noise + power loss hits even when fully warmed up and has almost rendered the vehicle unmovable.

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