Sorry for not responding sooner I haven't visited this sight in a while.
Before I say anything I want to let you know I am not a auto professional; I have just been around for a long time and have seen a lot. (Lol) It is always best to seek out a professional.
With that being said, here is my opinion.
Engine light going on and off:
If it wasn't the brake fluid level that I suggested in my first reply then it could be any number of the sensors. Sensors send signals to the ECU, the ECU then reacts to these signals. There are just to many sensors to name, but it's a good place to start. A signal from a sensor would not indicate that the sensor itself is bad, but rather something in that circuit is the problem or the device that its protecting is at fault. Example: A sensor in the brake line senses that the fluid level has droped below a unacceptable level and in return illuminates the engin light. On most newer vehicles fault codes are read from the flashes of the check engine light.
Now, I can relate to this problem, no not me the car (lol). Sure sounds like the upper control arm assembly. This item is located behind the engine next to the fire wall. Round cylinder with rods extending from both sides of the cylinder; if this part goes bad then the car will react in the manner that you have described. However, bad CV joints, ball joints, and alignmet can also cause the car to jerk, but it is usually promient to the side that is bad. If your car pulls to the right and you have to compensate it by turning the steering wheel to the left or vise versa. Then I would bet on it being the upper control arm assembly.
Sry, forgot about your question, do I think it could be the cat? Yes, it's a good possibility. The manifild absolute pressure sensoor could be senseing a presure difference from a back flow of pressure caused by a restriction in the cat, but yes the cats' maps could be indicating a retricted orfice usually a mild but gentle laxative with a can of tuna fish surfices.
Another tail tail sign of a bad cat, " is not that it meows all the time" but rather there is a signifigant temperature difference before the cat and after it. Example: 400 degrees before cat and 100 degrees after.
My mama always said that us simpltons had to keep it simple so's that we could better understand the rest of the world and with a smile on her face she said, "KISS, KISS, " now run along and play.
I hope this helps good luck.
Monday, June 26th, 2006 AT 11:14 PM