Hopefully this is the right section, if not maybe a mod can move it. And sorry in advance for it being so long.

On to the question. I have a JDM OBD0 B16A swap in my '91da also chipped ECU from Xenocrom, just a basic generic map, It has been in the car running awesome for 2 years roughtly, about 2 months ago I did a LS bottom end on it for some more torque, and ran fine for about 6 weeks, I started to notice that the car was running kinda ruff when backing off the throttle or when just getting on it from coasting. My AEM wideband now reads that at Idle and while coasting in neutral with no load on the engine I have a A/F of 10.0:1, and while under load it is anywhere from 15.4 to 13.2 depending on RPM, I also have 40 psi of fuel pressure at idle which is where it has been for 2 years as well, no change there.

Usually the A/F reads 17.8:1 or great (off the scale) while coasting and the under load A/F is unchanged from what it is now, about 15.4-13.2.

So it seems it is running pretty rich while there is no load on the motor. I just re-ringed the motor last week, new bearings, etc, it was burning oil and overdue for a bottom end rebuild (which i didn't do when I slapped the LS bottom end in) So I figured the excess oil was causing it to not burn the gas or something.

Put new plugs in the motor yesterday and was out breaking in the motor, instantly noticed the A/F problem is still there, so I pulled around the block and back in the garage.

Figured maybe a injector was stuck open or something so I checked all the plugs, none of them appear to have excess fuel on them, or fuel smell.


Can anyone suggest where I might start looking next?

 

Yeah i suggest you get a laptop, and start datalogging. If you already have that then start tuning.

 

But this is a new problem, nothing changed, so it is probably not simply tuning, you need to fix any problems before you start trying to tune it, otherwise if the problem goes away on it's own or becomes intermittent, than your tune won't mean crap anyway..


Any suggestions on how to actually fix my problem?

 

Anyone else? I'm going to throw a stock Fuel Pressure Reg on it and see what happens, might try to find some injectors to throw in it as well (they are all clicking perfectly, but one might not be closing all the way I guess) Last thing I can do is throw in a ECU.

After that I'm so lost, I have no vacuum leaks and checked to make sure the FPR was actually fluctuating with vacuum changes.