MaroonC63

So i got my secondaries deleted with straight pipes and resonators with an hpipe. Everything was fine for a week then yesterday a CEL came up. Code p0171 bank 1 running lean. I flashed it back to stock ( i have EC v4 tune ) and it went away after 20 miles. Decided id put the tune back on, then cel 100 miles later. I still have warranty up to 100k miles, 52k on the dash at the moment. The cel has been on since last night. Would they try to blame it on my pipes and void my warranty?

andrew c230k

Did you do anything to your air filters or air boxes ? I got this code when I took out my carbon filters and ran K&N's. The car flowed too much air outside the perimeters of what Benz set it up to do.

MaroonC63

Took our charcoals at 45k miles, got the same CEL, put them back on and didn't get the cel ever again, untill yesterday...

Could it be my straight pipe/h pipe set-up? To my understanding there arn't any senors where the secondaries and resonators are so it shouldn't of been the cause of the CEL?

Merc63

It can be a few things, all very common.

1. Intake manifold is leaking.
2. Valve for the fuel tank gases is faulty.
3. Air is seeping past the MAF on the intake where the big oval clamp is holding the air cleaner box to the tubing.

BerBer63

I think I had the same...passenger side o2 sensor died. Don't remember if it was upstream or downstream.
Purge valve comes to mind too.

Merc63

Switch O2 sensors side to side to rule them out. If problem continues on other side of the engine, you have your issue.

MaroonC63

Thanks for the reply guys, thought it was a more serious issue. Ill just flash it back to stock and let the dealership take care of it. Might as well use my extended warranty.