I had codes pulled I was told it was the catalytic converter, downstream O2 sensor, and map sensor. Replaced the catalytic converter and clean sensors, took off negative on battery and engine light went off but returned saying code 3 misfire on 4th cylinder. Replaced all five spark plugs and now the car says try sift up or slown down in my message box and check engine light flashes. I can get RPM to 3000 but speed to 20 mph, once I make a complete stop car barely wants to move and rattles or knocks. Great on gas but lately guzzling it so fast. What should I change or fix or what should I do.

 

The car is still misfiring. How were the condition of the coils?

 

My brother in law is checking them as we speak

 

That was my problem, they have been changed and the engine light went off. I can now go over 20 mph.
Hank you damien360 for the timely response! !!!