Greetings ~ HAPPY 4th
THANK YOU for YOUR WORK and CHANNELS
2010 Mitsubishi Lancer (5dr Sportback Man GTS)
2.4L DOHC MIVEC I4 engine (Non - Turbo)
TRANS AXEL: F10JA CVT?
VIN: JA32X8HW5AU005828
MILEAGE 208K - Used recent acquisition
CODE: 0420 Below Catalyst Threshold
Previous owner told would need new converter - typical and maybe not always!
*AFTER using CRC Carb and Throttle and finishing up with CRC MASS AIR on AtoF and O2 sensor(s)
*MASS AIR spayed and cleaned correctly with clean filter
NO CODES! AND there were no previous or subsequent Idle surges ~ constant steady and smooth
*Short term APPEARS very healthy at the jump around 0% ~ .08% ~ -1.6% ~ + 2.3% etc
Question is on LongTerm Fuel Trim:
In a perfect world 0% is my understanding (both sides)
Idle and drive is now at - 1.3% ~ 2.6% ~ -3.3% ~ -5.5%
Very stable and steady, not much jump around between these values
(and with some 0% in the beginning just AFTER clean)
So, CLOSED LOOP (no code with trigger on check eng light)
Would like your weigh in please on LTFT
*I have read that negative values indicates the burn is on the RICH mixture side
BOTH Lean and Rich have been referenced and stated in mechanics blogs for NEGATIVE long term fuel trim.
I BELIEVE negative for long term is RICH side condition
In addition, For short term I have an understanding:
Anything + or minus as a full 8 is fine?
For long term:
Anything + or minus 10 is fine?
OR is the 10 used combined for these two values short and long?
CAT STILL HAS LIFE
Chris64
Huntsville, AL
For long term:
Anything + or minus 10 is fine?OR is the 10 used combined for these two values short and long?
I'm not quite sure what you're asking. +10% or whatever, both long-term and short-term fuel trims indicate the engine is running lean and the engine is attempting compensate for it by adding more fuel. If you have negative fuel trims (anything negative), the engine is running too rich and it's attempting to lean out the mixture.
Ideally, you want long-term fuel trims to be as close to 0 as possible. I have a 1999 Ranger with 294,000 miles on it, and long-term fuel trim only averages around -3 or -4%. Cars don't trip their check engine lights until they're around +/-20%. My 1999 Ranger started running a little bit off a couple years ago, so I hooked up a scan tool and selected live data. Long-term fuel trims were at -12-15%. I put a bottle of Royal Purple fuel system cleaner in at 3/4 of a tank, and it started running better again.
Those are good numbers. I'm trying to get my truck to that point. Keeps running borderline lean. Lean can damage the engine. Since you have a lower percentage of fuel more of your power stroke is due to compression which results in increased heat buildup in the combustion chamber.
