I will use this to see if I can see any problems with the valves. I'm not sure what to do at this point, but there clearly seems to be an issue with the idle logic of the Long Term Fuel Trim part of Closed Loop. 7:1, which means 14. Car was stumbling and stuttering for a while with +10 LTFT and a low MAP.
Today I'll go for a good drive and check short term fuel trim, as I've read today that it's more important than long term. Interesting to note that the ECU so far is completely happy, no lights on the dash after disconnecting the AFM! Fuel trim tables are based on engine load, which is mostly determined by air mass. Make sense of Long term fuel trim. If the desired AFR wasn't achieved the PCM will decide what corrections are needed to correct the AFR (this is fuel trim). If the HO2S indicates the engine is running lean, the PCM corrects the lean condition by moving the STFT into the positive range, adding more fuel to correct for the lean condition.
At cruise, the Ranger hardly noticed the exhaust was plugged. Make sense of Long term fuel trim... Spark plugs were a good colour if a bit worn: Fitted new plugs and coils all round. •Observe the PIDs with the engine rpm at 2500.
Fuel trim is the PCM's adaptive strategy that allows it to deal with these issues by adjusting the amount of fuel that is injected into the engine, but only once it is in closed loop operation. You can use a can of carb cleaner/brake cleaner and gently spray around gaskets and hoses while the car is idling. I hope this article helps you to diagnose these nasty lean codes. How on earth can I reconnect this vacuum line to the intake manifold?!? The correct siemens/VDO unit (£160 on sale) cured it all. Fuel trim for diagnostics | Vehicle Service Pros. This causes a temporary instant rich in the system since it has now bled off all the metered air.
I have carried out this test and it is 101KPA, so this suggests the MAP is good, however I will test this over a range of vacuum levels. LTFT and STFT are percentages which represent the adjustment to the fuel injector pulse width. Suspicious of an intake leak, I installed my smoke machine, but the intake was not the issue, neither was the brake booster or the hose. Long term fuel trim high at idle capacity. The outcome of these two different fuel control systems is the same: an engine that produces good power, runs efficiently and has a clean exhaust. Be very careful when using propane; it's very flammable.
Went ahead and did it any way. The diaphragm in the PCV oil separator assembly had ruptured, allowing full manifold vacuum to enter the engine (some manufactures will supply a crankcase pressure or vacuum readings for diagnostics, although GM doesn't for this vehicle). The fuel trims will return to almost normal during cruise and wide-open throttle when the throttle plate is open and there is little vacuum in the intake but lots of air flow into the engine. The second minor thing is that when trying to restrict the closed loop trims don't use 0% - use 1% or -1%. This air comes crashing into your turbine wheel trying to spin it the opposite direction. Positive Fuel Trim, Throttle Open At Idle. Day after day, we work on cars with drivability problems.
To get full-access, you need to register for a FREE account. 6 then it rises to 7. It's a 20 year old car so I would expect the car to need to overfuel slightly as the injectors are no doubt a bit dirty. If your engine is a 4 cylinder, then it has only one bank, Bank 1. I've used a home-made smoke tester connected to a track pump which pressurised the intake assembly pretty effectively, so much so that undoing the oil fill cap (which is attached to the intake via various means) gave an audible 'whump' noise. The lambda is going rich but the injector duration is not changing. Long-term fuel trims are measured over longer time intervals by oxygen -, or air fuel ratio sensors downstream of the catalytic converter, and in practice, the signal voltages these sensors generate are not directly implicated in fuel delivery strategies, although there some exceptions to this rule. Long term fuel trim high at idle power. Each bank has its own fuel trim reading.
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. Verifying that a vehicle is in fuel control is important and looking at the fuel trim values can be a valuable diagnostic tool to find drivability issues. Please let me know what you think. Thank you in advance for your help and sorry if the post was confusing at all. This gives the illusion that the MAF must be at fault but it's still an air leak somewhere. The STFT was at +22% and the LTFT at +20%, and these trims were occurring at idle on a warmed-up engine. Long-term fuel trim values. Each of the two fuel management systems have their strengths and their weaknesses, but all in all, each of them does a pretty good job of keeping an engine running smoothly, efficiently and with a clean exhaust. Long term fuel trim high at idle control. Listen very carefully for any change in idle. The garage which fitted it was also the same place that failed to replace the spark plugs.... You can drive around like this lightly, - the ecu just defaults to a nominal value for airflow. I'll retest though, as it's fairly easy to do, just need to buy some more baby oil for the smoke machine.
When using propane enrichment, slowly move the propane source along all likely vacuum leak locations while monitoring the O2 sensors. As a final test, I simply went in and re-enabled the LTFT values and loaded the tune. Thank you in advance! Post your own photos in our Members Gallery.
An underreporting MAF sensor will cause a lean condition. I can't see where the hose goes either, but it seems like it goes into the intake manifold. 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. The STFTs are usually near zero, so it looks like it's not catastrophically bad, just weird.
In a fully functional engine management system, the signal voltage of the upstream sensor fluctuates rapidly as a result of changes that occur in the composition of the exhaust stream. If it isn't fixing the issue with that hose it is something that needed to be taken care of otherwise. At this point it seems safer to drive the car around with all Closed Loop values set to 0 until we can figure it out. Replacing the fuel pump fixed the major issue of the car not running however these numbers don't seem optimal from what I've read but my boyfriend is unconcerned by them. So it's important to look up reference values for the engine you're working on. The power runs through a 5-speed automatic transmission and the odometer shows 250, 000 miles have been traveled. Other possibilities are a faulty O2 sensor or leaking injectors. Stevieturbo said: And presumably this hasn't happened overnight? I think at 9 you should get a CEL.
Further inspection showed that fuel pressure was fine, temperature was OK, it entered into closed loop and that there were no vacuum leaks present. Did a few more 1-2 gear pulls to verify consistency in this issue, and then parked the car to let it idle for a bit. Hopefully that all made sense. The goal of the PCM is to maintain the appropriate AFR, and by using its fuel maps as a starting point, it will calculate the specific amount of fuel to inject. I would expect the +15% STFT to bring the LTFT from -10% to +5% after sitting for a long time. NOTE: Many manufactures are also using rear fuel trim to further fine-tune their fueling strategy. 9 volts, which the ECU interprets as changes in the oxygen content of the exhaust stream. 7 while bank 2 was steady at 3. To ensure optimal combustion three elements must be delivered in exact measure: fuel, air and ignition. You must be logged in to reply to this topic. The more ethanol, the higher the water level will rise past your mark. It never came back up. But when the engine is in boost mode and positive pressure is provided in the intake, the vacuum leak will allow boost air to escape.