Hello everybody! I have a 97 Sunfire GT with the 2.4L DOHC. The issue is one minute it runs great, the next it will barely pull itself down the road, no acceleration, back firing through the intake, black smoke coming out the exhaust. Trouble codes are 0171, 1133. I replaced the spark plugs, boots, the "battleship" looking distributor cap and O2 sensor all at the same time. No change. It doesn't matter if it's hot or cold, rain or shine, first thing in the morning or half way threw the day. It's totally intermittent. I hope some here can give some insight because my next step involves a gallon of gas and a match.

P0171 System too Lean (Bank 1) - Read Our Article On Oxygen Sensor Codes For Help With This Generic Check Engine Light Code

O.K. I couldn't find the Oxygen Sensor Codes article so I did alot of searching on the web. It appears a vacuum leak, especially at the intake, can trip this code. I pulled the intake off to look for any signs of leaking and found that a previous repair had neglected to clean the surfaces sufficiently and found a folded edge of the gasket. I replaced the gasket, cleaned the mating surfaces, torqued everything to specs and haven't had a problem in three days. Hopefully this helps someone in the future because this was an expensive and frustrating PITA to find.

Also keep an eye on the MAP sensor hose, they like to crack and give false MAP readings.