I have a 1997 Honda Civic LX. A few months ago my check engine light was on and I had cylinder misfires, so I had new spark plugs installed with new wires and a few days later the Check Engine light went off. About 2 months ago I noticed the Check Engine light came back on. I went in for an oil change and they notified me that I had a broken axle boot (that wasn't urgent) and an oil leak definitely around the valve cover. They also read the codes from the Check Engine Light. Last week I installed a new valve cover gasket, and the leak doesn't seem as bad, if existing at all. Since my oil change I've been having a new issue.

When I first start the car in the morning, the car runs fine. Only when the car is WARMED up do I have an issue where the car stalls when I come to a stop. If I press the gas pedal it will not stall, but if I come to a stop it very often turns off/stalls and I have to turn the key and start the car again. It always starts up right away. When the car gets warm and I can tell that I might stall, I've also noticed that the steering of the car gets slightly stiffer. But again, when I run the car cold, it runs great. I also never feel misfiring like I did before I changed my spark plugs. The check engine light is on and here are the six codes that I got when I got my oil changed:

p0171 Air/Fuel Mixture System Lean Bank 1
p0301 Cylinder Number 1 Misfire Detected
p0302 Cylinder Number 2 Misfire Detected
p0303 Cylinder Number 3 Misfire Detected
p0304 Cylinder Number 4 Misfire Detected
and -p1300

If anyone has any advice on where I should look to detect the issue, that would be appreciated! Thanks!