Hi all. Recently i installed a test pipe on my 07 TL (replace third cat) on my otherwise stock car. I was hoping for a little mpg gain but started to see problems. I have a bluetooth adaptor plugged into the OBD port to monitor all the systems of the car. It is very similar to a scangauge. as others have noted when you let off the gas and coast your car shuts the fuel off completely which i had noticed as well. since i installed the test pipe it no longer shuts the fuel off when coasting. i was wondering if the test pipe would cause this or something else happened at the same time to the car as coincidence. i cant put the 3rd cat back on as i had the test pipe welded in. anyone else notice this?
thanks

 

since there are no sensors on the third cat, its hard to believe this.


since, you cant put the third cat back on, you cant test your theory....

 

i find it hard to believe as well, just thought someone else with a scangauge with a test pipe could check their car

 

in for test's.

 

Does your scan tool have a logging feature? If it does, record it and post it up for all to see.

 

I'll check and see, never thought of that

 

i couldnt find any sort of logging feature

 

welded testpipe? better hope you don't fail emissions lol.

 

i'm up here in Canada so we don't have emissions tests and its a few years away so I wasnt too worried about that!

 

I don't have scangauge but I use garmin mechanic to monitor realtime MPG/fuel consumption.

it never cuts fuel, according to the computer but I always get more MPG than what OBD2 calculates. so I just think it does cut fuel.. but somehow it's not being read by OBD2 port like..