flashmayo
Veteran Member
Hi,
This issue has made the car nearly useless to me as I commute daily over a ~2K ft grade that causes the limp mode driving in either direction. I really need to figure this out. Any suggestions are appreciated.
The vehicle is a 03 Jetta 5 Speed TDI. Getting P0299 kicking in under lighter and lighter load conditions. It used to be just on uphill in 5th gear going just above 50 mph and trying to maintain speed or accelerate. Now it will go into limp mode just on a moderate slope trying to accelerate even from 60 mph plus.
Here's what I've done to troubleshoot:
New vacuum hoses all around.
Tested MAF against a spare with no change in result.
Swapped N75 with N18, no change. Swapped back.
New fuel filter.
New Air Filter.
Tested vacuum from vacuum pump, > 25in/Hg
Tested vacuum coming from N75 to VNT at 20.5 in/Hg
Pulled vacuum on a line connecting to the VNT and it held steady at 25 in/Hg.
The following were learned with the help of MaTT, one of the local TDI Gurus, who also did my timing belt job.
Using VCDS to cycle the N75, the actuator on the VNT moved to the stop.
He noted a normal amount of play in the turbo. Not sure if that means the vane plate or the actual turbine.
After looking at it for 2-3 hours he was stumped.
So it looks like the vacuum system is working properly, and it also looks like the VNT is operating normally. Yet I am getting limp mode often, occasionally accompanied by a CEL with the P0299 code.
VCDS shows that actual boost curve sits significantly below the expected curve. Alarmingly so according to Matt. With no noises that would normally accompany a intake leak.
Couple more things to add........
The timing belt was done about 1 week before this round of limp mode started showing up. Previous to that I thought I had it beat by doing much of the above. The limp mode has appeared intermittently for the entire 7 years I have owned this vehicle. I think the timing of the timing belt job and these symptoms are coincidental, but could be relevant.
I had previously removed the intake as part of trying to figure out limp mode, back at about 90K miles. There is now 190K on the car. During the 2 plus hour session with Matt, the EGR was removed and the intake has only a slight sheen of oil on the insides, no coking to speak of at all. This leads me to thinking that the turbo and actuator are relatively clean as well.
What's next? Pull the turbo and do a complete cleaning?
Thanks,
John
This issue has made the car nearly useless to me as I commute daily over a ~2K ft grade that causes the limp mode driving in either direction. I really need to figure this out. Any suggestions are appreciated.
The vehicle is a 03 Jetta 5 Speed TDI. Getting P0299 kicking in under lighter and lighter load conditions. It used to be just on uphill in 5th gear going just above 50 mph and trying to maintain speed or accelerate. Now it will go into limp mode just on a moderate slope trying to accelerate even from 60 mph plus.
Here's what I've done to troubleshoot:
New vacuum hoses all around.
Tested MAF against a spare with no change in result.
Swapped N75 with N18, no change. Swapped back.
New fuel filter.
New Air Filter.
Tested vacuum from vacuum pump, > 25in/Hg
Tested vacuum coming from N75 to VNT at 20.5 in/Hg
Pulled vacuum on a line connecting to the VNT and it held steady at 25 in/Hg.
The following were learned with the help of MaTT, one of the local TDI Gurus, who also did my timing belt job.
Using VCDS to cycle the N75, the actuator on the VNT moved to the stop.
He noted a normal amount of play in the turbo. Not sure if that means the vane plate or the actual turbine.
After looking at it for 2-3 hours he was stumped.
So it looks like the vacuum system is working properly, and it also looks like the VNT is operating normally. Yet I am getting limp mode often, occasionally accompanied by a CEL with the P0299 code.
VCDS shows that actual boost curve sits significantly below the expected curve. Alarmingly so according to Matt. With no noises that would normally accompany a intake leak.
Couple more things to add........
The timing belt was done about 1 week before this round of limp mode started showing up. Previous to that I thought I had it beat by doing much of the above. The limp mode has appeared intermittently for the entire 7 years I have owned this vehicle. I think the timing of the timing belt job and these symptoms are coincidental, but could be relevant.
I had previously removed the intake as part of trying to figure out limp mode, back at about 90K miles. There is now 190K on the car. During the 2 plus hour session with Matt, the EGR was removed and the intake has only a slight sheen of oil on the insides, no coking to speak of at all. This leads me to thinking that the turbo and actuator are relatively clean as well.
What's next? Pull the turbo and do a complete cleaning?
Thanks,
John