1996 Bonneville Engine Problems / ABS

First check your oil level on th estick with engine off.
Fill with 10w-30 to full mark.
If you are leaking a lot of oil. You will lose an engine quickly.

The brakes are the easier problem.
The vibration is warped front rotors. You need new front pads and front brake rotors.
There is a great picture tutorial on this site that shows you how to do it. It is not too hard on the fronts. The backs can be a pain.
Where you get the parts is your call.
Many feel the dealer ones are much better than aftermarket especially on rotors. They are at least somewhat better.
That being said. Most all garages, except dealers, use aftermarket parts.
I have had great success with several aftermarket brands of rotors and brake pads.
While there are parts I won't install unless they are factory original. On some I can't justify the price difference.
Also worth noting: it is rare for a dealer to offer any type of warranty on a rotor or on pads. Unless they install them. I have seen 90 days on rotors.
Many aftermarket stores even though the warranties are getting shorter. Many have at least a year on rotors and limited lifetime on pads. A few years back many were 2 years on rotors and some still are.
A lot of it depends on how long you plan on keeoing the car etc.
The abs light is common and usually doesn;t change the feel or function of the brakes. You just won't have anti locks. Most cars are able to lock up and slide the tires when the light is on. Like in the snow.
A sensor is on each front wheel. Near the hub. It is mounted near a ring that spins with the wheel. If the sensor gets too much metal shaving dust on it(it's magnetic) ir can cause a light. It can also be damaged at the tip or the wires going to them can get cut or frayed from rubbing against things.

Your driving issue could be more serious.
The RPMS should drop down quite a bit when it shift into overdrive (4th ) gear. You doing the gas thing just get you back into 3rd. It sounds like it is missing badly and running rough and low on power so you notice it uphill under a load and when it shift into overdrive.
You probably have a bad miss and need a tune up. Could be a cylinder not firing due to a bad coil pack. Pretty common on 3800s. But they are GREAT engines!
Get the codes read. That check engine light might give us some insight as to why it is low on poser.
You could also have a big vacuum leak or crossed plug wires.
Has anyone worked on the spark plugs or wires lately or is is possible that someone could have crossed some wires as a prank. I have seen this several times.

Hey Toby,

Thank you so much for your reply!

I took the car up to an auto place and had them run them check the code. One of the Cylinders was not firing. So I bought a new set of wires and plugs and installed them. The car now seems to idle smoother and doesn't "jerk" real bad when giving it gas. But that being said it still drops 1200 RPM or so when giving it light steady gas. This happens across the MPH range more then I first though. So that might rule out the overdrive problem? I also took the car out of overdrive and the problem was re-produced, if that means anything.

Anyhow I still am getting the RPM drop, its still VERY doggy on the throttle. I even romp on it more to over come the drop in RPMS but it feels like im trying to drive into a heavy wind. The RPMs climb but the car isnt not accelerating correctly.

My Oil leak is slow, its dripping a smal quarter sized spot a night, so I put more oil in it. I had the pan gasket replaced last summer so now I'm worried its leaking somewhere much more expensive to fix? I know thats impossible to help with over the internet but just wanted to make note of it.

Do you think it could be the catalytic converter?

-Mark