'06 Cobalt Engine Problem

I have a '06 Cobalt LS 2.2L that is having problems. It has thrown some codes P0128 ECT Sensor Below Thermostat Regulating Temp
P0455 EVAP System Large Leak
P0496 EVAP Canister Purge System High Purge Flow
and a few P0300 Random Misfires

It also threw a TPS code (which I have replaced), Fuel Filter (replaced), Fuel Cap (replaced), the EVAP Canister has been replaced also. My husband has been under the rear of the car and inspected all the lines and fitting, plus the canister and all electrical. The Mass Airflow was replaced as well.

The large leak detected code is the only one that hasn't been solved (aside of the obvious misfire).

It is still misfiring and sputtering and when I push the gas it won't go fast at all. It will eventually get up to speed but it takes it forever. Also it is going through gas like crazy (no leaks anywhere I have checked EVERYWHERE). I am not sure what else to do. Also sometimes when it idles it is fine, and other times it idles so low it acts like it is going to die. Thanks in advance for any info and advice. - Jennifer

It almost sounds like the timing chain jumped or something. I would confirm the timing it so good might be the timing sensor.

This codes are thrown for a faulty gas cap too. Check that first. Its much cheaper

Sent from my Z981 using Tapatalk

Of course check the simpler cheaper things first when chasing a problem!