Air Induction | Throttle Body
📝 P2101 ETCS Malfunction | Dirty Throttle Plate | 2014 Acura RLX
- P2101 ETCS System Malfunction
- Prior to cleaning, in ECM Live Data “TB opening angle” was no lower than 2 degrees with “Motor Duty” about -60%.
- ECM had a hard time keeping TB closed.
- After cleaning, “TB opening angle” became 1 degrees, “Motor Duty” about -17%
📝 Rich Fuel Trim, ECM120D | Dirty Throttle Plate | 2005 Volvo XC70 2.5L
- ECM120D code is a mismatch between the air measured by the MAF vs the air calculated
- Let’s say the car is idling and the ECM expects to see 3 grams/second air flow for 5% throttle opening.
- As the car gets a few miles on it the throttle plates get dirty and now the throttle plate is at 17% to keep the idle speed where it needs to be but the air flow is still 3 grams a second.
- The ECM expects to see a higher air flow at that throttle %. (iatn)
Idle Relearn | GM
- Tip: Key ON Engine OFF. If engine will be running, procedure will not succeed (e.g. 2008 GMC Yukon)
Throttle Position – Injector Pulse Comparison
Why does a dirty throttle body cause stalling problems?
- Idle Loads’ = anything that would add a “load’ to the crankshaft and cause an RPM drop.
- Examples: AC clutch on, alternator loads, automatic transmission placed in gear, high power steering pressure, etc.
- The PCM only allows a certain range for all idle load compensation.
- Example 1. An IAC stepper can operate in 256 different positions. However, the manufacturer may only allow a range from 0 to 50 to control all warm engine idle loads. When the throttle body gets dirty, all of the allotted idle counts will be used up just to keep the engine idling normally without any idle loads. Once loads are added, there isn’t enough compensation left to properly control the idle speed. This will cause intermittent stalling problems.
- Example 2. In an ETC system the throttle plate can be controlled from 0 to 100% opening. However idle load compensation (when your foot is off the gas pedal) is only given a 15-20% window of operation. Once the throttle plate gets dirty, the throttle percentage needs to be higher just to compensate for the carbon build up. This limits how much control the PCM will allow for idle loads. This may cause intermittent stalling problems and idle speed control trouble codes.