So I finally got the exhaust leak fixed in my Formula (it was at the bottom of the header near the exhaust). Found one where the header meets the block as well, but that's for another day. At least now I won't choke on exhaust.

I was surprised to find that the car actually runs better now- it hadn't thrown any codes or anything, but it definitely runs better- feels stronger. Kinda weird.

That makes sense especially if the leak was before the 02 sensor.

Yeah, it was. I thought it'd throw a code if it were to adjust settings that much.

I'm surprised that it didn't either since the OBD II cars seem to throw a code at the least little thing but it probably didn't since it sounds like it was before and after the front O2 sensor and that's the one that controls the air/fuel ratio and those don't usually throw a code unless they're not working correctly (constantly reading too low or too high). Now if it was the one after the cat then it probably would have thrown one.

I didn't take a real good look, but are there 4 O2 sensors? Looks like two upstream of the cats and two downstream.

Yea the OBD II cars have 4 O2 sensors - two before the cats and 2 after them. The 2 before the cats are for helping determine the air/fuel ratio and the 2 after the cats are for emissions only. And with your car being OBD II and having the 4 sensors you can get 18 different codes thrown by them.

Dang. I think it's really cool that it has two cats though- some cars only have one like my 85.

Yea it is sorta cool that it has two cats but it can be a pita if there's a problem and it can be expensive too, espeically if you've got to replace both of them. Oh and our cars only got two cats starting in 1996, before that they just had one.

Gotcha- if my cats go, I'll just weld in straight pipe and go with 02 sims.

So I got the exhaust leak all taken care of. Dang, it's like the car grew two extra cylinders! I thought it was fast before!

Cool on getting it fixed and that you're car is running a whole lot better now.

Thanks. The car really is about 50% more fun with it fixed. I didn't even know it was running funny until the leaks were fixed. Previous owner putting a hole in the header with an air tool and me having to get it welded FTMFL.

Yea it's amazing what a little exhaust leak can do to how a car runs. But it's cool that you're finding out just how much fun your car can be.

those O2 sensors can really mess with your car if something's not right.
depending on the location of the leak, it could mess with the knock sensor too me thinks

I'll bet you're right- my 87 Monte Carlo LS with 305 will pick up ticking like that and retard timing. It really sucks how sensitive it is.

By the way, does this board really need flood control? It's not that busy. I usually disable it on my sites unless I'm getting pegged constantly with spammers.