I bought a 85 with a 3.1 swaped in and it is burning rich. 1/2 tank 100km. I only have one o2 sensor connected, i am quit sure that both should be connected but i can only find one spot on the 3.1 ecm for the o2 sensor. Should there not be two?

nope. at least by the info given. I dont think they had 2 O2 sensors until they switched the name to "3100". or SFI. the 3.1 MPFI only had the one O2 sensor.

anyways - which 3.1 you got - 3.1 iron head, 3.1 mpfi or 3100 sfi?

I belive it is an 3.1 mpfi it has injectors not a throttle body. Th exhaust manifold they used has 2 o2 sensor locations one on each side. I was hopping i would not have to spend the coin on 6 new injectors (possible leaking one )

well, the 3.1 mpfi has a wide flat top inatke manifold which says right on it: 3.1 Multi Port Fuel Injection (mpfi)
it uses 1 O2 sensor. on cars that use 2 - one goes before the cat conv - the other goes after the cat conv.

send the injectors out for cleaning & flow testing. some places will even swap out a "way out" injector for one that more closely matches you set.
or maybe even goto a junk yard, and get an extra one and send 7 in, and then select the 6 closest matches. leaky injector is usually due to build-up. cleaning usually fixes it.

also - symptom of a leaky injector is - the car is hard to start when when hot. it'll crank, but hard to start, due to flooding from the leaky injector. also - the fuel system wont hold pressure. you can hook up a fuel pressur eguage, turn on the key, watch the pressure hit around 40 (if leaky - may not make it). when you turn the key off again - the pressure should hold. and maybe SLOWLY drop. as in take 15 min - 1/2 hour to drop just halfway to 20. any quicker, and - yes, good chance its a leaky injector, spraying fuel.....

thanks i will give the pressure test a try. It does not have a hard time starting so mabey i have a sensor out.
Thanks
Pete

quote Originally posted by cold fiero: thanks i will give the pressure test a try. It does not have a hard time starting so mabey i have a sensor out. Thanks Pete

just "hot" starting. like, when you go into a store, grab a pop, come back, and try and start - and it seems to crank ALOT longer than usual. due to the fuel which leaked past the injector, and flooded that cyl's spark plug.