Knock and the loss of power

[sunster]

I looking for some guidance, I have a '96 Lumina 3.1 that occasionally upon start up there would be a loud knocking noise coming from the rear passenger side of the engine compartment. When driven in this state the car will continue to have the rhythmic knocking sound but lacks power from a stopped position. It feels like it is surging and the trans also slow to shift out of first gear. The problem is not constant, I would return to the car after some time and it would run fine without the noise. There has been times when the car starts up with the knocking noise and then just stops after sitting idle just after a few minutes.

Can anyone point me in a direction that I should start looking? Let me know if you have further questions.

Thanks in advance.

[maxwedge]

Engine type noises are difficult at best to try and diagnose, someone has to listen to this onsite and offer some advice as to whether it seems to be internal/lower end or in the valve train. You could pull the valve cover in the area of the noise and confirm proper valve/rocker arm actuation. A high mileage engine that has been poorly maintained could develop a sludging condition that could cause this , no way to pinpoint the issue from here.

[1973chevelle]

piston slap i think i have a 1995 lumina it shakes and u can hav u foot all the way down on the gas and the rpm will be up to 3.5 and once it gets to 30 it has all the power . and going up hill it has no power but the rpm is high . took ut to a gm shop and they said it was a piston slap and it was time for a new motor cuz my motor had 200,000 miles on it

[sad-lumina-owner]

Some gas stations have crappy gas. or water in the gas. This is very common.

Try keeping track of where you are buying the gas and see if there's a correlation. Buy it from one place 2 or 3 times (flush out tank) and then switch for a few fillups.

If you are using regular switch to high-octaine premium, or a blend.




Maybe you got something very wrong going on in your neighbourhood.

[jeffcoslacker]

Rear passenger side makes me think of belt tensioner arm, which will produce a pretty convincing imitation of an internal knock if it's worn and really being forced to whip around rapidly...which a dragging belt driven accessory or worn tensioner pulley bearing can do...

Watch it when it's making the noise sometime, see if it's hopping around wildly and making noise. If so, pull the belt off and see what's dragging.

Shot in the dark, but rule out the easy/external causes first....