When you close the throttle body while the turbo is spooling, the pressure on bottom is greater than the pressure on top, so the piston opens. Don't have the AC running while you do this. Apologies, I can't get them to load in order.
When it comes to diagnosing emission related diagnostic trouble codes, it is very important you are aware of what fuel/air management system you are working on. 1 At idle, the LTFT always goes deep into negative numbers trying to pull fuel. A slight rise in water level, about ¼ to ½ in., is about 10% to 15% ethanol. IS there a working CEL at all? Be aware that some four-cylinder and straight six engines will split the cylinders into two banks (BK1 and BK2). In this case the idle would be low and you don't state the idle rpm are low. Now that you've verified that the DTCs are P0171 and/or P0174, and the fuel trims exceed the threshold, it's time for a visual inspection. Registered users of the site do not see these ads. Total fuel trim is an additive value: STFT+LTFT=Total Fuel Trim. This is not to say that it's really knackered, it just doesn't have the zing that other cars do. LTFT and STFT are percentages which represent the adjustment to the fuel injector pulse width. Last but not least is a weak fuel injector and or fuel pressure. I have literally spent dozens and dozens and dozens of hours on this issue that continues to baffle me. High LTFT at Idle. - ScannerDanner Forum. If it reads NO, the vehicle must be driven until the FF percentage can be learned.
That mist goes everywhere. The PCM will operate in two distinct fuel control modes: open or closed loop. The exhaust is now not leaking, but the LTFT remains at 25%. Im getting so tired of trying to find the problem, but I don't want to give up at all! Long term fuel trim high at idle speed. They do tend to rise as the airflow increases and drop as the airflow decreases (see - the 15 minutes stuck in traffic) which lead me to a low fuel pressure diagnosis initially. Interesting to note that the ECU so far is completely happy, no lights on the dash after disconnecting the AFM! Basic Mass Airflow Strategies. Fuel control drivability complaints and the issues that accompany them are a frequent concern in most shops.
Post the calibration as well as datalogs showing what you are describing. Spark plugs and coils are all new. TIP: Bear in mind that fuel trim values are only reliable if it is known that the oxygen -, or air/fuel ratio sensors are fully functional and in closed loop operation, and that there are no air/fuel metering or ignition related codes stored. I have 'RS' engine mounts - so not ridiculous ones - and am wondering if that, along with a resonator bung (now removed) which is a common mod to increase the induction noise could have together been creating a strange frequency which caused the issue. I should make clear that it's not running really roughly, just a bit lumpy and lacking a little bit of pep. Positive Fuel Trim, Throttle Open At Idle. The bottom is connected to the intake pre-throttle body post-turbo, and the top is connected to the intake manifold. The evap solenoid is closed at idle. Adding STFT +LTFT = +42% of total fuel trim when the code was set; it was obvious the PCM was adding fuel to compensate for an issue. Mass airflow engine air calculations are the simplest for me to understand. Link after it was pulled out:). Coincidentally (or maybe not?
If you connect a scan tool to such a vehicle, both the short and long-term fuel trim data will be displayed as percentages. The LFTF value is stored in memory and "learns" from the STFT. With the issue it dyno'd at 260bhp, will take it back to the same place (Surrey Rolling Road) and see how many horses I've released! They tend not to leak oil but will suck air. But if the sensor is proportionally under reporting it might cause behavior like this. O2 sensors are functioning as expected. High positive fuel trim at idle. You seem like you are picking up on this stuff pretty quick. There is no winning here. It then monitors STFT and stores the FF inferred (FF_INF) value.
5:1 to 14:1 AFR) for maximum power and the PCM may also request a richer mixture to prevent detonation under certain conditions. 6L three-valve engine and a vacuum leak. But having JUST fixed a vacuum leak, I'd expect the fuel trims to be LESS rich not more!? 0 tsfi, ltft at IDLE=13. These engines are sensitive to un-metered air, loose oil filler caps and even a dip stick that isn't installed properly or has a torn O-ring is enough to cause a fuel trim and MAF codes on these engines, but my visual inspection had turned up nothing. Exhaust restrictions can set a P0172/P0175 (System Rich: Banks 1 and 2)) codes on some vehicles, depending on how the sensor software is written. One rogue spark from an ignition wire or coil could surely ruin your day. I can't find any leaks anywhere. I noticed the previous owner fitted a new MAF - could this be a poor copy? The vehicles that come to our shops use one of two types of fuel management strategies: speed-density or mass airflow as measured by the mass airflow (MAF) sensor. 1 is a 2001 Ford Ranger powered by a 4. Long term fuel trim high at idle engine. Then I applied the bone stock fuel trims as you asked, and the ECU decides it wants to pull 12-15% fuel at idle until the both the STFT and LTFT is super duper rich. When testing, if you strike an obvious problem, stop and do not go any further because all subsequent results will be invalid.
Below are some tips and tricks to diagnose the most common faults /defects / failures /malfunctions that cause rich air/fuel mixtures that result in high negative fuel trim values-. However, once the deviation reaches about 25% with the engine running at a steady speed, there is a problem that will almost always be indicated by a rich or lean running trouble code. Each different vehicle manufacturer will use the inputs of these sensors differently, so don't think just because the GM product you worked on yesterday calculated air mass one way that Subaru that's here today will be the same. Can you get another? STFT adjustments happen almost immediately, but these changes are just temporary. Do you have a code scanner that can read live data, if so the air flow should be in there somewhere. I tried to remove the dip stick to check the integral positive crankcase ventilation (PCV) valve in the cam cover for an issue and the cause of the problem was uncovered. What is their common failure profile? Im putting this down to denser air because its approximately 15 degrees C cooler then when I last tested. Fuel Trim: Finding a Vacuum Leak and Performance Issues Using Fuel Trim Data | Auto Service Professional. NOTE: On some applications, most notably some GM products, the oxygen sensors are electrically opposite, meaning that a low signal voltage indicates a rich mixture, as opposed to the lean mixture it would indicate on most other applications. Car idles fine at 650-800 RPM at all times, even with AC on.
For example, the STFT could be +3% and LTFT would be around -2%, and it would not bring the LTFT any closer to 0% while holding this for 20 minutes. Clearly this is less of an issue when the throttle is open.