My engine shakes and sounds as if something is misfiring?

Question

I own a 2002 Cadillac Seville STS. Since I bought the car, the engine seems to shake and misfire but only when I pull to a stop. Like when I stop at a light my car shakes...not violently but enough to bother me...especially when I am low on fuel, not empty but low. When I refill I use Chevron Techron Concentrate Plus and fill up with supreme Chevron gas. After maybe 20min on the freeway, when I stop again, the shaking and misfires seem to stop. I was told it may be a catalytic converter but after reading yahoo answers, it doesn't seem to be. Any advice??? Aside from the obvious to take it in...

Answer 1

could be nothing more than gas cap not holding pressure.

Your car can tell you what's wrong...just take it to autozone & ask 'em to "read the codes".

Answer 2

your car is old enough to start having sensor problems. you have  many sensors that send specific information to the ECM to help it calibrate the air, fuel and timing needed to run at optimal performance. as one other has sugjested 1st off go to auto zone or who ever will offer free tool rentals and get a system diognostic to see if codes have been thrown write them down and then go into the counter person and ask them for the read out for those codes. they dont often just say "replace the oxygen sensor" but rather problem found in the emissions system possible sensor" this is just an example of course. I will advise you if you should ever change the cats change the oxy sensors as well, this is like buying shoes with no laces. you have a very good engine there and worth the time to make it right. great advice Pedro about running low on fuel and i'll add when you keep the fuel level above 1/2 you get better millage as it keeps the fuel cooler.

Answer 3

get free scan at advance auto or other fine prts store...anything else just guessing...any why are u letting in run low on gas,,,bad for fuel pump and injectors