Check Engine Light after installing HKS drop in air filter
 

Installed the HKS Super Hybrid Air Filter a few months ago and got codes; P0171 P117B P1170. Redid the install the next day and found out I didn't fit the the air box tightly.

This weekend the codes came back so I checked the air box and everything was snug so I dropped the car off at a shop. The shop tech told me the codes are being caused by my cat-back because "your cat-back is creating back pressure which is causing you to run lean".

Can anyone verify if this would be true? Only exhaust mods done to my car are the HKS Hi-Power Spec-L cat-back and the drop if filter if you count that...

Blasphemy! Lol

Car fucked. Burn it. Don't bother selling that pos.

Buy a new Civic Si. Problem solved.









Sounds like you got some gunk in either or both throttle body or Mass air flow sensor.


I always take off the whole intake box when changing filters. Too much fuckery if I don't. It's only 4 bolts and one connector.

Jesus you know life sucks when the easiest “mod” goes wrong lmao

I would say just take time to triple check if everything is clean and tight. Wouldn’t worry about it too much. Also, wouldn’t listen to the tech...or take your car there again. Too much back pressure? If that’s the case, every single car with an aftermarket catback would have a check engine light lol

A quick search shows they are indeed lean codes. I would be looking for a leak in the intake or exhaust system. Check all the connection's on your intake are tight. Not just where the filter sits but every connection. It could also be an exhaust leak near the header. Last of all it could be a O2 sensor failure. A cat back is unlikely to cause extra back pressure and even if it did i doubt it would cause enough of a restriction to alter the mixtures out of range of the ECU.

Also check this thread:
http://www.ft86club.com/forums/showthread.php?p=2128963