PLEASE HELP! 99 Cobra Throwing Lean Codes and Stalling During Cold Starts


New Member
Nov 22, 2021
Troy, Il
I bought a 99 cobra and it ran great and had no problems. I thought that the engine bay was a little boring though so i decided to get the valve covers powder coated. I went through hell and back to get them off and back on but i ended up finishing it. It looked great and I liked the result but when i went to start it, it would idle really low. I just adjusted the idle screw and went about my day even though the exhaust smelled kinda rich and didn't want to always stay going during a cold start. Later on I took it in the get inspected and it wouldn't pass due to what they called "cat system not ready", couldn't fix it for the life of me so i took it in and my mechanic said he thought it might be the ecu, so i got a new stock ecu with the stock tune. It didn't fix the emissions problem but i just ended up moving my address so i wouldn't have to pass emissions. Then I decided to replace the O2 sensors and when i went to start it up after that it started throwing 2 codes (P0171 and P0174) "System Too Lean Bank 1 and System Too Lean Bank 2". I then noticed the my IAC valve was consistently open so i replaced it, then I found out that I had put the throttle body gasket on wrong during the valve cover job, fixing that solved the IAC problem. But it was still had a lean code and i though i might be caused by an exhaust leak so i completely examined the exhaust system and there was what i thought might be a slight exhaust leak so i fixed it and cleared all my codes, i didnt throw a code for a awhile but still had the cold start problem but i didnt mind it. But about 2-3 weeks later my engine light come back on and it is still have the cold start problem. if you have any clue what this could be PLEASE HELP ME.
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...I can take it. I think.
Mod Dude
Mar 2, 2003
Sea of Tranquility
If it was fine before you took the valve covers off, go back and make sure everything is back where it should be. Kind of sounds like a vacuum leak.