New Header Bad News, Need Advice Please
 

So the problem is:
I went down to pick up my 1990 n/a at the exhaust shop where the header was extensively modified to fit and installed. They had to bend the down pipe and lengthen the O2 sensor wire which the location is now right in front of the cat.
So I started it and let it run for a minute or two, to warm up a little. Then I was playing with the throttle a little to see how it sounds. That’s when it went wrong, it died. I restarted it and found it easy to start but now running very rich(lots of black smoke) and really rough .
So my thoughts are that the o2 sensor might have got fouled by the burning of the paint because I had repainted the whole header before it was installed. I will be going back down to the shop tomorrow since the car is stuck there. I’m just trying to get some advice since I want the shop to look at it before I start messing with it. I did not disconnect the o2 sensor since it was hard wired in. That was my first thought. So any help is much appreciated, Thanks.

Thats a strange one
 

I don't know much about the O2 sensor. Curious as to why you would think it could cause the car to die? Back Smoke usually means carbon being burned doesn't it? I have only seen that during fuel injection cleaning and such, Thanks, Scott

Because the o2 sensor ajusts the fuel/air mixture my measuring the oxygen in the exhaust, hence the name.

Ok
 

OK thats cool, but how can that lead to burning black smoke? Anyway Thanks for all your help I found my problem on the red Supra you have been helping me with the timing belt must have jumped. The belt is in real bad shape but not broken. Cracked and missing teeth. Timing marks are off by quite a bit! Has to be why it died. I will come back to this thread though and hope to learn more about the O2 sensor. I have never replaced one or had to. Thanks, Scott

you painted the inside of your exhaust? also the toyota o2 is wierd it could just be because of its placement it reads completely backward of a normal o2 i doubt it would cause this though my o2 is bad and i run 15.0 -15.7 afr at idle warm and 11.3-13.0 afr at wot 3rd gear on a 700-6500 rpm pull the shop might have just missed something or left something unplugged

I didn't paint the inside on purpose but i'm sure some paint made its way in there.

just overspray wouldnt be enough to foul your o2 its built to have carbon chunks thrown at it and its always coated with unburnt fuel and carbon

howd you like the sound before it died though?

it sounded good but cost way too much

do you know what all needed to be modified? besides the dp

make the stud holes bigger

make the o2 sensor fit right

bend the downpipe

get band clamps for connection between downpipe and header

grind the main flange to fit the head

seems like alot of work just for a header i hope my obx doesnt need as much work im hoping to just bolt it in and go lol

the problem is that they seem to look the same

3" Exhaust
 

At what point does the exhaust expand to 3" for what everyone is calling a 3" exhaust. Does this type of exhaust connect to the stock headers? Does it expand from the cat convert back?

yes the 3 inch is a cat back system the header replaces the cat though for a full catless exhaust but its a 2 inch pipe then joins into your ehxaust whether it be stock or oversized

So I got it to settle down now after disconnecting the sensor and it took alittle bit but smoothed out. I'm think that the sensor is too far back in the pipe and not getting hot enough.

sounds reasonable though it should be self heating and it doesnt go off of heat it actually reads a/f ratio did they put the sensor up off of the exhaust? like did they use an anti fouler or anything to compensate for the cat alot of muffler shops will do this thinking its necessary because their used to doing newer cars

its just a normal o2 senor, but what do you mean by anti fouler?

alot of people use a sparkplug anti fouler (found at autozone or advanced auto in the help section) it raises the o2 up out of the exhaust and limits the flow to basically simulate a working cat

In the old cast iron manifold the sensor is pretty well in the flow with it being between the two banks of 3 about 6in from the exhaust ports. Now what i'm trying to do is figure out if I can weld the downpipe to the header and still be able to get it out of the car.I'd like to wrap it further down and knock down some of the noise coming from it. It sounds like a v8 with open headers under the hood now. And I plan on moving the o2 location up the pipe much farther. It does make a nice inprovement in power though, not sure how much but noticable.

ill let you know in about 2 weeks lol doing a base line pull on my car this week since it is very close to stock only has a cold air and crappy 2.5 with single cat then next week im getting my header (gotta pay registration this week and freaking florida raised there prices) but i finally got my clutch and installed it

my header will be a bit different though its gonna be the obx but ill be modifying it at the last y where it merges into a single im gonna get rid of the y and just use 3 inch tube as a collector then do a straight 3 inch all the way back with just 2 45s in it so it should flow real nice and quick for all you haters on the 3 inch on n/a

should give you a close idea of the power gain though in real world rwhp numbers on a mustang dyno