Hi guys, i have a is250 2007 with 230k km on it. It has a intermittent problem of hesitation and loss of power. Both of my short term fuel trims are close to -20 when idling but as soon as i accelerate it goes between +5/-5. My long term fuel trims are both close to -20 as well.
Changed spark plugs
Changed fuel pump
changed injectors
Any ideas?
thanks

 

Having experienced this with my Fsport lower air box. Once the MAF readings get out of wack. Both STFT, and LTFT will read -20% rich. This was happening because my air filter was getting saturated with water.

You have to wipe the ECU fuel trims to a clean slate.

Did you disconnect the battery when doing all this work?

I'd start with geting a new air filter if milage is unknown, and cleaning the MAF with CRC MAF Cleaner

ECU Reset: To me the fuse method is the easiest.

https://www.clublexus.com/how-tos/a/...our-ecu-363500

After the reset the LTFTs should start off at 0. Then monitor the trims.

 

okay yeah i've tried resetting my ecu a couple of times between each parts replaced but the trims came back not long after. I'll change the air filter in case and reset it to monitor my trims and i'll come back with my readings.
thanks

 

@MikeFig82
Help me out here but I think a vacuum leak results in positive trims while a bad o2 sensor(s), plugs not firing, result in negative trims as the ecm is pulling back fueling.

If this were mine;
Monitor the following:
MAF and O2 sensors using obd port and software.
Check for exhaust leaks.
If plugs are past 75k miles, replace them and inspect for carbon build up in intake ports. No air or starved for air means negative trims.

That's what comes to mind initially.