BuckeyeMan71
Veteran Member
Lately I’ve been noticing that my Jetta wagen has been taking longer to build boost. Where should I start looking
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
Turbo
- Thread starter BuckeyeMan71
- Start date
oilhammer
Certified Volkswagen Nut & Vendor
Exactly how do you know this?
BuckeyeMan71
Veteran Member
When I push down on the pedal the car goes but sometimes I have to let off pedal and I’m not flooring it to get the boost to kick in
Sent from my iPhone using Tapatalk
CalvinM
Well-known member
We can try and point you in a direction, but it makes it a lot easier to diagnose if you can get someone with VCDS to help you.
Since the turbo in our cars is controlled by a vacuum actuator it is common to have problems with the vacuum system and/or actuator. The actuators have a tendency to rust out and no longer hold vacuum. Also it could be stuck vanes within the turbo.
best way to check both is get under the car and apply vacuum to the actuator nipple to see if it moves and the correct vacuum. you can also try and move the vanes by hand to see if they are stuck.
One piece of advice is also to do some of your own homework before you ask questions.
The best way to search TDIclub is by via a google search.
Enter something like this into google. "Site:tdiclub.com alh no boost"
Since the turbo in our cars is controlled by a vacuum actuator it is common to have problems with the vacuum system and/or actuator. The actuators have a tendency to rust out and no longer hold vacuum. Also it could be stuck vanes within the turbo.
best way to check both is get under the car and apply vacuum to the actuator nipple to see if it moves and the correct vacuum. you can also try and move the vanes by hand to see if they are stuck.
One piece of advice is also to do some of your own homework before you ask questions.
The best way to search TDIclub is by via a google search.
Enter something like this into google. "Site:tdiclub.com alh no boost"
oilhammer
Certified Volkswagen Nut & Vendor
So your actual complaint (the first 'C') is low/inconsistent power? You jumped to the cause (the second 'C') without addressing the first.
Complaint
Cause
Correction
The ECU controls, and thus monitors, boost. Which can be viewed (actual vs. requested) in the scan data. If it gets too far off... typically even before there is any complaint... the ECU will flag a DTC and turn the MIL on. Do you have that?
Now that we have your first C, we can go after the second. Common things that could cause low power besides boost are the MAF, and the injectors, and even the intake/EGR.
Complaint
Cause
Correction
The ECU controls, and thus monitors, boost. Which can be viewed (actual vs. requested) in the scan data. If it gets too far off... typically even before there is any complaint... the ECU will flag a DTC and turn the MIL on. Do you have that?
Now that we have your first C, we can go after the second. Common things that could cause low power besides boost are the MAF, and the injectors, and even the intake/EGR.
BuckeyeMan71
Veteran Member
No lights are on. I have replaced all vacuum lines put a new egr in and I have my own VCDS cable and since no lights are on the dash didn’t know if it could help locate the problem.
Sent from my iPhone using Tapatalk
oilhammer
Certified Volkswagen Nut & Vendor
You can check the MAF, actual vs. specified, in the engine data, Measuring Group 003.
Best to do this while driving... a weak MAF may only top out around ~500 or so. It should be pretty linear as the RPMs climb under consistent load.
Really bad MAFs can be diagnosed by simply unplugging it, and going for a spin. If it runs better, (but won't be 100%) the MAF is for sure bad. But could still be marginal even if it does not run better.
Boost actual vs. requested can also be checked in the scan data.
Best to do this while driving... a weak MAF may only top out around ~500 or so. It should be pretty linear as the RPMs climb under consistent load.
Really bad MAFs can be diagnosed by simply unplugging it, and going for a spin. If it runs better, (but won't be 100%) the MAF is for sure bad. But could still be marginal even if it does not run better.
Boost actual vs. requested can also be checked in the scan data.
snakeye
Veteran Member
Is it limp mode? I find that during limp mode, pressing the throttle halfway will feel like it gives more power than during wot.
If your left hand fits behind the engine, you could reach back there and press the actuator arm down and feel whether it's moving smoothly. That's the first place I'd look.
Vince Waldon
Top Post Dawg
The Low-power HOW-TO in my sig is a great way to investigate this step-by-step.
Also worth noting that there can be codes set with no CEL on, so a full VCDS auto-scan for codes is an excellent step to start with.
Also worth noting that there can be codes set with no CEL on, so a full VCDS auto-scan for codes is an excellent step to start with.
BuckeyeMan71
Veteran Member
300D
Veteran Member
Pretty helpful guide to logging using VCDS: https://malonetuning.com/assets/files/vagcom_logging_guide.pdf
If you think it's a boost issue, the results from following that PDF will tell you heaps.
If you think it's a boost issue, the results from following that PDF will tell you heaps.
oilhammer
Certified Volkswagen Nut & Vendor
Yeah, see again you are assigning "loss of boost" as your compliant.... and your complaint is "low power". You'll have a difficult time diagnosing something if you are already stuck on something it may not be. If there was a loss of boost, the ECU would know it, the MIL would be on, and you'd have a happy P0299 low boost pressure regulation stored, and the car most certainly WOULD be in limp mode.... it would be blatantly obvious.
I've given you a couple data points to monitor with a scan tool while you drive. Takes ~45 seconds and a ~1 mile stretch of road. This is why so many turbochargers get replaced that never needed to be. Same nonsense with people assigning ALL hard cold starts to some problem with the glow system.