ok my 88 s4 car has a 91 s5 engine
has an s4 ecu and wiring harness w/ electricals
vdi wired open and no 5/6 port sleeves and no emmissions
gets 10-15 mpg on average

replaced the following:

ecu (2x)
coolant thermosensor
afm
o2 sensor
intake temp sensor
fuel pump (now running auto zone special)
spark plugs (over and over)
leading and trailing coils(2x)
spark plug wires
fuel injectors (cleaned and flow tested)

i have checked timing
i know of other cars with the same swap that run fine
butt dyno and gas milage tell me im running rich as well as the 2 foot blue flames...

wtf could it be?
any ideas, i thought about going safc but i want to fix this first so i dont accidentally fix it and lean way out.

 

no one has any ideas?
im completly stumped.

 

come on guys should i just stick an safc on it? or what?

 

lets try it once agin...
any one have any thoughts?
the s4 and s5 engines dont have a signifigant difference in fuel economy to explin this guys

 

Ok..If it's Guess time Dreyko..(since I don't have a friggin clue either)..What about the Injectors?..are they "in sync" with the ECU's?..that is to say are the Injectors (low impedance?..High Impedance?),and is the ECU the same For the Injectors?.

 

yep its both high impedence 1988 style injectors and ecu

 

check your wiring on the S5 intake manifolds that may be the problem. also what pullies did you use the s4 and s5 pullies are slightly different and will throw off your timing

 

I was going to suggest timing. Not that it will change your AFR but it wil help burn the air and fuel better.

To find TDC, remove the main bolt in the pulley and point the keyway slot with the exhaust side of the motor. Mark the pulley, then start advancing slowly. There is a sit that show you how to make the marks on the pulley for the different degrees but I don't remember where it is.

 

Maybe the variable resistor is messed up? Does not that affect all driving conditions? Try turning it more lean, also maybe its an FPR? Clogged return line?

 

the veriable resistor only adjusts the AFR in closed loop.