running l/t's without tune

[#1stangFAN]

Well im installing Longtubes and an o/r h-pipe in my car right now and bamachips said it would take at the most 3 buesiness days to send me my new tunes but i already have tunes from him for my cai and gears. So i was wondering since ill finish up the install tommrow would it be safe to run the car for a couple days without the right tune or is that a no go? I know ill flip a light because i have no cats but other then that would i have to worry about anything else?

 

[gmantheman]

I believe your A/F will be off.

 

[NastyStang113]

No you will be fine to run it for a few days. It will throw a CEL but it'll be okay. It might run slightly leaner as in a few tenths of a point but it wont hurt anything.

 

[Marc S]

I agree, it will be a little leaner but nothing to worry about. I checked my A/F before and after my L/T install.

 

[echoinsilence]

just dont bash on the motor, and you'll be good, just like everyone else has already said lol

 

[mustangford289]

Long tubes

I was unable to drive my car after installing LT's before I put the tune in. It threw a code as soon as I tried to move and did not allow the engine to rev at all. Maybe these other guys have a different experience?

 

[Rob72]

I was under the impression that the rear O2's just relayed to the ECM that the cats were working properly but had no effect on engine performance.

 

[StonePony]

It is the front O2 sensors that cause the problems after a header install. You can turn off the rear O2s if you dont need to pass an ODBII emissions test. The fronts may throw a DTC for not being heated fast enough. That can be adjusted in the tune.

 

[NastyStang113]

I was under the impression that the rear O2's just relayed to the ECM that the cats were working properly but had no effect on engine performance.

That's correct. Longtubes in some cases can lean a motor out slightly but it's so minimal that unless you're tune is on the ragged edge you will not have a problem.