Thread: poor fuel economy and surging

I have a 01 se 3.1. The ses light wasn't on and i scanned the codes and got a p0128 or 6. It was coolant temp below thermostat level or something. I wrote it down and can't find it now. The mileage is really bad now just like that. I was driving to work today watching the fuel gage go down. I am thinking like 15 mpg. I used to get about 27 the last time i checked. I put a new air filter and plug wires on last week. It also surges in gear when you are up to speed and holding the throttle steady. Something like 5-750 rpms up and down. 1500-2250 area. I'm going to change t-stat but does anyone have any input to this. I just replaced the vent solenoid and gas cap to clear the p0446 code but now this.

Coolant is green, rad is flushed. GM crate 3.1 with 3500 miles. Its runnin too cool and is in "choke" mode i think. I don't have emissions testing so i'm gonna gut the cats as well as clean maf. I have a dtc code reader so i can check codes again later.

It isn't throwing codes anymore. It had a thermostat below level code and before it had the p0446 evap error. I think it must be mechanical problem like exhaust restriction mabe. I would think that it would be more noticeable under throttle than barely gassin it at highway speed tho. I am gonna pull a plug and check how black they are. Also i am getting about 25 mpg after i checked it. I am also going to check for vac leaks cause it makes a slight hiss somewhere. This is sort of a wierd problem i have never encountered before. Almost like it doesn't want to keep the tc locked up or it is getting a bad ground. It seems to only happen when i get about 20-30 miles on it. I am gettin close to due for a trans filter so i am going to put some jb or lucas in there when i do it also.

Now i have two codes p0446 again with a new purge solenoid so something must be effed up in the wiring and a p0742 torque converter clutch stuck on. I went for a ride and i noticed hard shifting on the way home so i scanned it again. I don't know if it might be the pressure switch poopin out or just the trans filter. I'm hoping to change that monday and it will be good to go.