arcking
Well-known member
I need some help! After a cold start (meaning that car has both been sitting for a number of hours AND that the temperature is cool - say 40F or below) my '04 with 225,000 miles won't get out of it's own way, even with full throttle applied. As an example of how bad it is, I'm not able make it up a set of standard car ramps without a running start or lengthy application of the throttle. If you stay on the throttle long enough, RPMs will slowly rise and the car comes to life at around 1,800 rpm. At higher RPMs or once the car is warmed up, it has the power it should. This problem has been present for some time - likely for the last 75,000 miles I've owned the car - but it seems to be getting worse over time. I'd appreciate any insight you all might have - I've been through the troubleshooting I can think of, but won't be surprised at all if I'm missing something simple! The car is stock as far as I'm aware with the exception of the EGR delete and upgrade to a VNT 17.
Here's a graph showing the slow response to the application of the throttle - you'll notice that the actual boost is not matching the specified boost, even though the VNT position is reported as changing. I'm not sure what to make of the actual boost not changing in response to the VNT actuator moving - is it typical for the boost to be unaffected by VNT position at an idle? I'm also not sure if the difference in the MAF (EGR) readings is an issue, especially since there's no EGR.
Also to note, when you compare engine torque to the smoke limiter (neither shown in the graph above) once it's warmed up a bit, but still low on power, you'll see that the charted lines are essentially superimposed indicating to me that that's where the torque limitation is - I've been told that the car smokes a slight amount when this occurs, so I think the limitation is legitimate (rather than a result of bad sensor data). I'm not sure if this is the case when it's barely moving though.
What I've done thus far:
Here's a graph showing the slow response to the application of the throttle - you'll notice that the actual boost is not matching the specified boost, even though the VNT position is reported as changing. I'm not sure what to make of the actual boost not changing in response to the VNT actuator moving - is it typical for the boost to be unaffected by VNT position at an idle? I'm also not sure if the difference in the MAF (EGR) readings is an issue, especially since there's no EGR.
Also to note, when you compare engine torque to the smoke limiter (neither shown in the graph above) once it's warmed up a bit, but still low on power, you'll see that the charted lines are essentially superimposed indicating to me that that's where the torque limitation is - I've been told that the car smokes a slight amount when this occurs, so I think the limitation is legitimate (rather than a result of bad sensor data). I'm not sure if this is the case when it's barely moving though.
What I've done thus far:
- Check for DTCs - none present
- Checked vacuum, including between N75 and turbo during operation - they seem to be close to what I'd expect
- Confirmed that the VNT actuator begins and ends at the desired vacuum levels
- Checked and adjusted torsion - was -2.5, now +0.5
- Checked that temp sensors (coolant, fuel, IAT) read similarly - they do
- Visually inspected all of the charge and intake air plumbing I could
- Check compression when warm per Bentley - 350-360 psi
- Tested with and without MAF, including a new MAF (spare)
- EGR & EGR cooler deleted
- Timing belt replaced
- Camshaft and lifters replaced
- Turbo replaced (VNT 17)
- Lift pump replaced
- MAF replaced
- Glow plugs replaced
- N75 replaced
- MAP sensor replaced
- Throttle pedal replaced
- Applied TSB 07-45 for hard starting
- Glow plug harness replaced
- Crank position sensor replaced
- Coolant temp sensor replaced
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