P701 fault

Hi everyone, I’m a new member here looking for some help on my Mum's MG 't really been used on the road since 2021. My dad used to start it every other month and check the coolant etc., until recently when it wouldn't start at all. We diagnosed a failed fuel pump, which I have now changed, as well as fuel filter The car is running again, but I’m struggling with a persistent P0170 (Fuel Trim Bank 1) fault and the idle is "hunting" between 900–940 RPM once warm.I have some live data from my OBD scanner and would appreciate any insight into why the idle won't settle:• TP (Throttle Position): Stuck at 3.9% at idle. I have tried the "5-pedal pumps" reset multiple times; it sometimes jumps to 14% or 3.6% during the process, but always settles back to exactly 3.9%.• MAP: 36 kPa (at idle).• ECT: 94^{\circ}\text{C} (Stable).• Long Term Fuel Trim: -5.5%.• O2 Sensor (Bank 1 Sensor 1): Reading steady around 0.815V (Rich).• Throttle Body: The butterfly is closing fully against the stop screw (which still has factory paint). The cable has plenty of 've done so far:1. Replaced Fuel Pump & added fresh petrol.2. Cleaned the throttle body butterfly valve and spindle.3. Removed the air filter to check for restrictions.4. Performed the TPS reset (ignition on, 5 floor-to-floor pumps).5. Noticed that when I unplug the TPS, the idle seems to stabilize significantly.

Can you provide somemore info like is it MG F or TF, what engine do you have, is it VVC engine or not, year of production?

Sorry MG TF 1.8l 135 2003 year 

I do not know how frequent you read live data but O2 sensor should fluctuate between 0.2 and 0.9 V. It should not be steady on any value as that would indicate faulty sensor.

Ok I’ll check that out, it’s just I had a few issues when I first got it going after changing pump and filter , it run for around 10 minutes then suddenly start behave erratic and then cut out , and would not start  , it would then start after 30 or so seconds cut out and repeated this process a few times slightly misfiring, then I had this fault so put on obd reader and reset fault , but it kept coming back occasionally, so left the obd connected to take readings and run it for a 1/2 hour or so , idling fluctuated from 900 - 930 

Are you sure that your new fuel pump is working as it should, since all what you said colud be down to fuel pump not working properly. Maybe worth to check electrical connections which you touched when changing of the pump was done.

Hi 
after doing a bit more research the Throttle position 3.9 % at idle at the same with engine off is correct, so the main issue is this p701 fault 

Unless I’m mistaken 

I had the same fault code, eventually traced it to the pre - cat O2 sensor.

Yeah the new one is working fine purchased from MGOC , the old one was seized up , and car would not fire at all , once changed and it fired up pretty much straight away