Hi folks,

Have a head scratcher I could use some help with. The cats were cut off and stolen a while ago, along with the 02 sensors. Got new downpipe with cats and sensors. Since then, she hasn't run the same. The last couple of weeks, it's been really bad- at a stop, the revs are low and occasionally stalls out. Also have a slight gas smell when running and MPG is waaayyy down. Also- changed oil around the same time and it's still a little overfilled. Not sure if these are related, or what. TIA for any suggestions...

 

I am far from an expert here, but my next step would be to pull a plug or two and see if they indicate rich. They will look very dark and slightly wet. Assuming that is the case, then I would start following the sensor trail.

My disco came with stolen cats, was missing the upstream O2 sensors and had one of the plugs on downstream ripped out. First stop on the sensor trail would be to validate that none of the plugs were damaged when the O2 sensors were "removed".

Another quick tip is to unplug the mass airflow sensor and see if it runs better. Having that sensor unplugged forces the computer to use a default fuel map based on RPM. If the sensor is bad, the car should run better with it unplugged.

I am sure others will chime in with better suggestions.

 

some good places to start there, much appreciate it. for some reason I thought the ECU did more active mapping and re-mapping, based on sensor input.

 

You might check and see if they rewired the O2 sensors correctly. I think they are sensitive to resistance and a poor wiring job might send mixed signals back to the ECU.

 

The suggestions above are a great place to start, are there no codes? A cheap ELM OBD dongle and some graphing software would give you a good idea of what the O2s are doing, and possibly other things as well. You might want to park somewhere you can monitor drips and make sure you're not leaking fuel as the result of a nicked pipe or something. Pretty remote chance because you'd have to leak a lot to affect the MPG that noticeably but possible.

 

Were the adaptive settings cleared when the new components were installed?