Can I tune these problems out of my 1.8 swap?
 

Hi, all, looking for a starting point for my car.

• 1990 1.6 chassis/wiring/OEM ECU
• 1995 1.8 motor swap
• 4 wire O2 sensor retrofit
• TPS unplugged (bad unit, will be replaced with vTPS when MSPNP goes in)
• 18 MPG

Driving down the road at a constant RPM yields a solid CEL. I jumped TEN and GRND and pulled these codes:

• 15 Oxygen sensor <0.55 V 180 sec after 1500 rpm
• 17 Oxygen sensor unchanged after 1500 rpm
• 34 ISC Valve

The odd thing about the O2 sensor is that it is a brand new Bosch 4 wire unit. I put it in after the 1.8 swap, and my post-swap MPG went from 15 to 23 MPG. Recently, it's gone back down to 18 MPG, so I assume the car is running rich somehow.

Two questions:
1. Do you have any suggestions as to what I should start looking at?
2. Is this something I can tune out of when I install my MSPNP 1.3 unit (and therefore don't have to worry about for now)? Car will be boosted soon, so I was wondering if the MS settings will override all of this and take care of it all.

Thanks all.

Car is running rich because your o2 sensor is bad.

MS will solve your issues since you won't have a reason to run an oem narrowband sensor.

MS settings won't override anything. You take the stock ECU out so you essentially start from scratch (i.e. basemap) for fueling etc.

You should learn to use the MS and figure out what everything means before you install FI unless you're paying someone else to do all the tuning and are towing the car around between the install and tune.

Okay - so that's reassuring. It makes sense too.

So why should a brand new O2 sensor fail so quickly? Any ideas?

And in regards to learning the MS: I am getting it tuned by a professional. I believe in my mechanical abilities but I don't trust my tuning abilities... not yet at least.

Are you sure it's not a fake? Where did you get it? There are fake 4.9 units on amazon. That could be it.

Also, if you have had the car running for a bit without the sensor plugged in, it probably died to spite you.