Hello! I bought a used chevy spark 2014 with lpg system a month ago. I had a P0172 error (system rich bank 1) and car had not a lot power, especially when it warmed up. I changed PCV valve which was faulty causing a hissing sound. The sound stopped and car's acceleration improved when engine warmed up. However, P0172 came back again after some miles. I changed the spark plugs which were not in very bad condition (although they were old). There was no sign of leakages or fuel/oil on the spark plugs (no indication of probable injectors' leakage). Same error code came up again. Additionally I have cleaned MAP sensor, air filter, air throttle body (which had a lot dirt). I checked the vacumm lines and there is no sign of leakage. I checked the EVAP purge valve and it is fully closed when disconnected by voltage. Short term fuel trim is now normal between -6 to +8 maximum. Long fuel trim goes to -20 under load. I suppose that the long fuel trim has not adapted to normal values yet, after the PCV valve change.

Also note that the car has difficulty to accelerate when it starts cold (before reaching operating temperature). If I press the gas too much it stalls. If I let the gas and press it again slowly it achieves to accelerate slowly. Especially, yesterday I had parked it under the sun for many hours (hot day) and it showed adversity to start and also a great power loss during acceleration for some time. After 1-2 miles, the car was operating normally again. Due to this fact I suspected that the EVAP purge valve is stack open and caused more fumes to the intake due to the hot weather yesterday. But I checked it and it is ok (closed when disconnected). Also, although the O2 upstream sensor seems to show a strange voltage diagram during acceleration, it could not cause any problems during open loop when starting the car, right?

I am out of ideas now. Anyone could help?

 

I took advice of others. Did transmission flush, completed tuneup along with replacing injectors and 02 sensors. Car is shifting fine but after 20-30 minutes it loses power and won’t move. It has to sit and “cool” for about 15 minutes and then it goes thru same cycle. My situation sounds somewhat similar. Have you found a resolve?

 

In my case, I finally cleaned the camshaft position sensor and reset the long fuel trims. No check engine light again and car runs fine. I had no problem with the shifting gear or transmission generally. However, your situation seems different. Can the car increase RPM smoothly when in neutral and warmed up?