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Ive been checking data on my OBD and I noted I have Long Fuel Trim on -25, short fuel trim are mostly +-5%, I wonder what may be causing this? , Engine with 210K miles, as far as I know this means ECU is injecting 25% less fuel, short fuel trims seems to be fine.
I have no CEL, but like a week ago I had P0172 & P0175 but they they were gone d after cleaning the MAF.
In the following vide capture from my OBD app, engine at working temperature, and values from idle and with 2.5k RPM.
Ive been checking data on my OBD and I noted I have Long Fuel Trim on -25, short fuel trim are mostly +-5%, I wonder what may be causing this? , Engine with 210K miles, as far as I know this means ECU is injecting 25% less fuel, short fuel trims seems to be fine.
I have no CEL, but like a week ago I had P0172 & P0175 but they they were gone d after cleaning the MAF.
Any input or help would be greatly appreciated.
Thanks in advance
Did you reset the ecu afterwards? Search the forums, or check a few threads down. If you clear the codes using generic scan tool it will not reset long terms. It must be done by ecu reset battery disconnect, or fuse method. Try that then look at your fuel trims. Battery method needs to be over 15 min. Fuse will do it in over 1 minute.
I did the ECU reset, and I can see just after I turned on the car I saw short fuel trims on negative 20% , like 30 seconds after the start up the long fuel trim changed again to -20% , so at this point I know there is something wrong with my car, maybe a O2 sensor or the Cats?
The moment I turned on the car Im sure thath spike in the middle of the A/F Ratio is the exact moment when the ECU changed the Long Fuel Trim After the ECU changed Long Fuel Trim
I did the ECU reset, and I can see just after I turned on the car I saw short fuel trims on negative 20% , like 30 seconds after the start up the long fuel trim changed again to -20% , so at this point I know there is something wrong with my car, maybe a O2 sensor or the Cats?
The moment I turned on the car Im sure thath spike in the middle of the A/F Ratio is the exact moment when the ECU changed the Long Fuel Trim After the ECU changed Long Fuel Trim
While the car on create a false leak. Pull a vacuum hose off to do this. See if the numbers go positive. I'd suspect MAF issues since it's pretty much affecting both banks equally.
How old is your air filter, and have you ever cleaned the charcoal filter on the air box top? 200k + miles it could be severely clogged up.
Are the fuel trims equally wonky on both banks? Try fiddling with the MAF plug while watching the short term numbers. Unplug and re-plug it several times, then start it up and watch if short term starts trying to balance out the long term (I.e. ST starts reading positive double digits while LT stays negative double digits).
My GS400 had similar symptoms and soldering in a new MAF plug solved it.
06-10-21, 11:26 AM
-25% Long Fuel Trim 2008 IS250
