I recently changed my spark plugs (2000 S80 T6) and a couple days after doing so I received a "Check Emissions" message and the check engine light came on. The P-Codes that came up are P0172 and P0175 (Fuel Rich banks 1 and 2).

I then discovered that I didn't seat one of the turbo lines properly so I fixed that and had the codes cleared. A couple days later the "Check Emissions" message reappeared again. I checked the vacuum lines as best I could and unplugged the battery to clear the code(s).

Upon starting the car this time, if felt like it was only firing on 2 or 3 cylinders and then finally smoothed out. I drove it for a couple hours with no issues and then the "Check Emissions" light reappeared.

This morning the car died on me after stopping for a red light. I was able to restart it and finish driving to work and decided to check under the hood to see if something had come loose. I noticed that one side of the intake manifold was warm and the other half was cool to the touch, after driving for almost 20 minutes.

I'm not quite sure where I should start troubleshooting. Electrical for the plugs, or vacuum system? Anyone have any ideas?

Thanks.

 

Check that the coils are seated correctly, and connected.

 

Thanks, I'll recheck them tonight.

 

No such luck! I took everything apart, reseated all the coils, ensured they were firmly connected, and unhooked the negative terminal for about 30 minutes.
After putting everything together, the car drove fine but about 20 miles later the "check emission" message and check engine light came back on! I'm guessing there are still P0172 and P0175 codes, but I'd have to pay another $10 to confirm it.
Any other thoughts? Thanks.

 

Check emission... gas cap, vac lines, throttle body?