Any LeSabre Mechs. or someone who had the same experience with this out there be kind enough to share some knowledge, I'd like to hear about it. I have a '93 LeSabre 90th. that recently started running very rough when my kid was driving it. He came to me and showed me and I've been trying to figure it out for a few days when I get time. When the engine is cold, it doesn't do this as noticably, but when the car gets warmed up and is in Park, it idles ok. When I put it in reverse or drive, it shakes while sitting still. When I drive very slow it shakes and when its up around 40mph, with foot on accelerator, the car vibrates with a low pitch noise as if your driving on a road with alot of lines cut in the pavement. When I let off the accelerator when its doing that, it stops vibrating. Could it be bad fuel, dirty fuel filter or catalytic converter? I put in fuel injector cleaner, but haven't driven it enuf yet to see if that helps.

 

Just out of curiosity, When was the last time you changed the plugs/ wires?

 

You can also check the engine mounts.. one might be getting bad, and it could be amplifying the vibrations of the motor. Does it seem to get worse at higher rpms?

 

I haven't changed the plugs or wires. I bought it from a mechanic relative who checked the car out pretty thoroughly and repaired things that were bad on it before I bought it from him a year and a half ago. I would think he wouldve caught that or maybe he changed them at the time. I'll have to ask him. Would it run smoother in park and neutral if the plugs were bad though? He suggested it to be maybe the EGR valve or similar type part that has to open/close. I replaced the EGR valve, but that didn't help. He lives 400miles away, so he cant check it out first hand.

 

It actually does this only when idling in gear, (shaking) and when it's at around 40-45mph, 5th gear(automatic) it starts vibrating.

It stops shaking at higher rpms when idling.

Driving at 5-35mph its been pretty smooth but lacks the acceleration power I think it should have at any speed.

When the engine is cold in the morning it doesn't shake while idling in gear noticably, but after it warms up it does.

Could Mounts cause it to act this way? Thanks for help

 

It's important to know exactly what you are trying to describe as shaking.
If the engine is losing one cylinder intermittently that would be described by some as a roughness, vibration, or shaking.
The best way to confirm this is to feel at the tail pipe exhaust when the car is in gear and feel the exhaust. If you can feel a popping type pressure then it would definitely be a misfire. If not then it has to be something else. Can you check that out and let us know just what you feel there?

 

If they're just starting to get bad, it could.

It don't sound like the mounts. If it were, then the vibrations would become more noticeable as the rpms rise. Is the check engine/service engine soon light on?

 

Yeah, there did seem to be a popping pressure there. But that was when it was running in Park. I guess I'll get help so I can check it in gear. I'll let you know...

 

No, they haven't come on at all.

 

Like hanky said, your problem is probably in the plugs/wires.