2012 A3 8P 2.0 TFSI Quattro
For the longest time I have been having an issue with my car falling flat on its face when accelerating hard from a stop. It does not do it every time - but is consistent. On hard acceleration when the engine requires maximum fuel delivery.
I have replaced the fuel filter and HPFP, checked the cam follower. This has not resolved it.
Normal hard acceleration once at speed does not produce the same issue.
When accelerating hard from a stop, the engine revs to almost about 4500-6500 RPM. Then suddenly just falls flat on its face. Like someone shut the ignition off - it does not stall, it just feels that abrupt. I take my foot off the accelerator, it stumbles a bit, then runs fine. It has never stalled, or misfired. I did get a code once - P2293 - Fuel Pressure Regulator - Low Fuel Rail Pressure. I didn't have time to deal with it at the time so I reset it and continued on.
Fuel delivery appears normal when I crank tested it and delivered fuel into a bottle. Running pressure was within required specs at idle - tested with a pressure gauge.
Today I finally had time to go for a drive and log some data in VCDS.
I chose
- RPM
- Fuel Rail Pressure Specified (FRP Specified)
- Fuel Rail Pressure Actual (FRP Actual)
- Low Pressure Fuel Pump Duty Cycle (LPFP Duty Cycle %) (which I read should be around 50%)
- Accel Pedal Position % (Accel %)
What I learned from looking at the data after.
The LPFP duty cycle is fairly consistent at 48-54%. It does spike to high 60% at points where the Accel Pedal % is high (hard acceleration). It does begin to climb as I accelerate hard, and then seems to fail as it peaks around 70%. This seems to make sense as the fuel pump is working harder. But not sure whether this high percentage duty cycle is acceptable - ie - would a brand new pump have the same high duty cycle % under the same parameters or would it always read around 50%?
The Specified and Actual Fuel rail pressures stay very consistent. Usually within one bar of each other. (I am thinking that is what should be expected)
On the 4 occasions today where I experienced the car falling on its face. I see in the logged data that when the Accel Pedal is at 99% (wide open throttle - accelerating from a stop) there comes a huge difference in the Specified and Actual Fuel Rail Pressures (Specified 150 - Actual 3.5) and the Fuel Pump duty cycle shows 79.2 %.
When the LPFP duty cycle is really high (79.2%) the actual Fuel Rail Pressure falls off to just 3.5 bar. This obviously is the issue. Fuel starvation under high demand.
This is consistent in all 4 of the logged events where I experienced the issue of it falling on its face.
My question: I am thinking the issue is with the LPFP - just tired and not being able to keep up with the high demand during hard acceleration and high fuel demand.
Is there any other parameters I should check? Or does this seem to point to the LPFP?
I can run some more tests. I just want to ensure this is the issue prior to buying a new LPFP.
I have attached a link to screen shots of the relevant events in the data. I can download all the data if that helps but I thought these screen shots would be enough to show what's going on. All the other data appears normal. Just these 4 events when I had the issue.
For the longest time I have been having an issue with my car falling flat on its face when accelerating hard from a stop. It does not do it every time - but is consistent. On hard acceleration when the engine requires maximum fuel delivery.
I have replaced the fuel filter and HPFP, checked the cam follower. This has not resolved it.
Normal hard acceleration once at speed does not produce the same issue.
When accelerating hard from a stop, the engine revs to almost about 4500-6500 RPM. Then suddenly just falls flat on its face. Like someone shut the ignition off - it does not stall, it just feels that abrupt. I take my foot off the accelerator, it stumbles a bit, then runs fine. It has never stalled, or misfired. I did get a code once - P2293 - Fuel Pressure Regulator - Low Fuel Rail Pressure. I didn't have time to deal with it at the time so I reset it and continued on.
Fuel delivery appears normal when I crank tested it and delivered fuel into a bottle. Running pressure was within required specs at idle - tested with a pressure gauge.
Today I finally had time to go for a drive and log some data in VCDS.
I chose
- RPM
- Fuel Rail Pressure Specified (FRP Specified)
- Fuel Rail Pressure Actual (FRP Actual)
- Low Pressure Fuel Pump Duty Cycle (LPFP Duty Cycle %) (which I read should be around 50%)
- Accel Pedal Position % (Accel %)
What I learned from looking at the data after.
The LPFP duty cycle is fairly consistent at 48-54%. It does spike to high 60% at points where the Accel Pedal % is high (hard acceleration). It does begin to climb as I accelerate hard, and then seems to fail as it peaks around 70%. This seems to make sense as the fuel pump is working harder. But not sure whether this high percentage duty cycle is acceptable - ie - would a brand new pump have the same high duty cycle % under the same parameters or would it always read around 50%?
The Specified and Actual Fuel rail pressures stay very consistent. Usually within one bar of each other. (I am thinking that is what should be expected)
On the 4 occasions today where I experienced the car falling on its face. I see in the logged data that when the Accel Pedal is at 99% (wide open throttle - accelerating from a stop) there comes a huge difference in the Specified and Actual Fuel Rail Pressures (Specified 150 - Actual 3.5) and the Fuel Pump duty cycle shows 79.2 %.
When the LPFP duty cycle is really high (79.2%) the actual Fuel Rail Pressure falls off to just 3.5 bar. This obviously is the issue. Fuel starvation under high demand.
This is consistent in all 4 of the logged events where I experienced the issue of it falling on its face.
My question: I am thinking the issue is with the LPFP - just tired and not being able to keep up with the high demand during hard acceleration and high fuel demand.
Is there any other parameters I should check? Or does this seem to point to the LPFP?
I can run some more tests. I just want to ensure this is the issue prior to buying a new LPFP.
I have attached a link to screen shots of the relevant events in the data. I can download all the data if that helps but I thought these screen shots would be enough to show what's going on. All the other data appears normal. Just these 4 events when I had the issue.
