Problems with 1991 Buick Century

DCIDRUMMER101

MEMBER
1991 GMC

I have a 1991 buick century, 2.5L 4 cylinder with 126000 miles. The problem im having is extremely intermittent so its hard to find out whats wrong. When I start it for the first time each day, it runs fine, but after awhile it starts shaking really bad, and I have to floor the accelerator to get out of 1st gear. If im accelerating too slowly it has a tendency to die on me. Basically it idles really rough and likes to stall out on me. I checked the diagnostic codes it gave me (33 and 34) which deals with my MAP sensor.I replaced the fuel filter, plugs and wires, and the 2/3 coil with no luck. My catalytic converter heats up real hot and turns orange when it does this, and the explaination i've been given is that raw fuel is being dumped into my exhaust because im only firing on two cylinders and its because of my ECM not working right. Could that be the cause? And if so, is it even worth fixing?

1 Reply

DEERAYROSE

MEMBER
25 POSTS

Your converter could be bad or plugged, causing too much back pressure. If not, it's likely to go bad very quickly due to all of that heat. Good way to catch on fire, as well. A simple way to check the converter is to remove the O2 sensor and run the car. If symptoms improve, start your tests with the O2 sensor, and work your way back.
Check the O2 sensor readings, Throttle Position Sensor, EGR Valve, and vacuum lines for leaks and plugs. Coolent sensor, thermostat, all sorts of things can contribute to a screwed up fuel system which can affect other things as well. For example, you may get a code for the MAP sensor, but something else could be causeing your MAP sensor to appear bad.
Your ECM could definetly be bad. If you test everything I've mentioned, and every single one shows up out of wack, I'd suspect the EMC.
Plugged or faulty injectors can cause these problems, as well as messed up wiring to those, or any other electrical component.
Check online in various places for information on simple home tests you can do on some of these parts. The more you test, you can narrow down the problem.