QuestionI got a repair shop to check out why my check engine light was on and I dont understand any of it.
121 maf sensor
113 fuel trim
232 adaptive fuel trim too lean or rich
could someone tell me what all that means and what i should do?
my car (on the highway) likes to sometime feel/sound like its stuck in overdrive.. the first time it did it i thought i accidently hit the overdrive button but when i pressed it it did nothing. when i turn the overdrive on it doesnt do anything ( like its already in overdrive) so anytime my car makes these noises/feelings its at 4rpms when it usually idles at like 2.5 on the highway when crusing. also its been eating gas like crazy. someone help!
Answer All right Anna, here's a quick lesson. Pay attention. MAF ='s mass airflow sensor. It measures the mass (quantity), density, and temperature of the incoming air into the engine. It is the main determiner of the fuel injection systems output to the motor. Fuel trim is achieved by what the exiting air's (exhaust) composition is. The oxygen sensor(s) "sniff" the exhaust for the presence of excess fuel. When detected, the voltage output increases and tells the ECU= electronic control unit = computer to reduce (trim) the amount of fuel being introduced to the engine. In other words, it adapts to changing conditins over the short term STFT (short term fuel trim) and the long term. LTFT (long term fuel trim) When it can no longer adjust the trim to meet emmissions, it turns on the check engine light and stores these codes. Whew, get all that? VBG
That's the basic setup. Other factors affect the system. Vacuum leaks and exhaust leaks especially. Most places start with replacing the oxygen sensor which rarely cures the problem. You need expensive test equipment and a brain to test them accurately. You need a gas analyzer and a labscope at minimum. Otherwise, it's just a guess. They are NOT cheap sensors. If they are recommending replacement, ask for a written gaurentee that that will fix the problem. Watch how fast they backpedal.
The VERY FIRST THING I would check would be the fuel pressure regulator as they are prone to failure.
It also sounds like you are having an overdrive problem. The RPM readings you gave are a dead give away. Wiring at the base of the shifter(especially manual gear models), the OD button (switch) itself and the overdrive relay itself are the most common pattern failure items. There are other components, but these are most likely.
HTH
Mark
