Ok CL, posting this up after doing hours of searching to help a fellow CL member with a rich idle issue. Recently installed an AEM UEGO and its reading 11.7 at idle, and cruising.

IIRC, his SC is a 97+, with a 5-speed Aristo swap with a single turbo (dont know the specs) running .8bar. The short ride I took in it, the car ran great, no black smoke, some white/blue from what is suspected bad valve seals. idle is very smooth, boosts just fine, but eats gas like crazy.

We are trying to plan a day to physically look at the car and touch some points with a multimeter, but I am trying to get ideas as a starting point, or to see if anyone has had the same issue.

Any info would be greatly appreciated, cause his car and the swap are both just way too clean and good looking to have an issue like this, and he doesnt drive the car too much due to the poor MPG's

 

What injectors and any piggyback?

 

stock 440cc jdm injectors and no piggyback just the jdm aristo ecu.

 

aftermarket fuel pump? maybe check fuel regulator and/or pressure.
does he still have the factory o2 sensors? the eugo cannot drive the stock ecu.

 

I was thinking the FPR, and yes stock GTE o2. The UEGO worked just fine on my na-t, both with and without piggy back..

 

Mine runs that AFR when cold idling, but when it warms up its dead on 14.8-15.6 15lbs of boost, thats on stock JDM injectors, HP255 and AFPR at 50lbs. To me it sounds like maybe your O2 sensor, also check vac line leak and codes if you can

 

Check vac line to the Map sensor. I had a similar issue and the vacuum line had completely come off the sensor. I did have a rough idle and lost power so it could be more of a partial vac leak to the sensor or a failing map sensor. Not a hundred percent on this, but a likely culprit.

Jason

 

It has the stock supra tt fuel pump and stock fuel pressure regulator.

 

i had running rich issues on my aristo swap due to a cracked vacuum line going to the map sensor. car ran perfect no problems just running rich all the time. check all your vac lines

 

so i checked the vacuum lines going to the map and all looks good. any other ideas or suggestions? could a bad o2 sensor cause this rich condition without a cel?

 

Did you check the vacuum line going to the regulator?

 

the Uego will always read fine on the gauge, but the stock ecu cannot read the narrowband results that the Uego can output due to the narrowband signal on the uego being a steady signal wherein a typical o2 sensor uses a really fast switching signal. the ecu will treat it like it is a "lazy" or worn out o2 sensor where the switching is below the threshold rate.

Are you using the o2 sensor that came with the swap? if so I would recommend putting a new sensor on it, it is an important sensor regardless if its the cause of this problem or not. it is possible for it to keep the ecu from entering closed loop, but even for open loop it sounds a little too rich but might be a good place to start.

does the temp gauge work? a bad temp sensor could make it think the engine is cold and hence the rich condition.

Did you do the 12v mod, if so double check the wiring.

 

Yeah, I did check the vacuum line going to the regulator. All of that looks fine. Any other suggestions?

 

Yeah I am using the o2 sensor that came with the swap. No check engine light, but I know that does not mean that the o2 sensor is still good. I am going to try to unplug the sensor to see if that does anything and switch out to another sensor from my friends car. The temp gauge does indeed work. I would have to check with my installer about the 12v mod. I am sure that he did it though or maybe he could have just done the fuel pump ecu bypass mod. Any other suggestions?