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SmoothCat565

Go Kart Newbie
Location
Massachusetts
Car(s)
2017 VW MKVII GTI
Am I on the right path here?

Basically, I've noticed that unplugging and replugging in my MAP sensor has done wonders for fixing a lot of weird behavior on my car, but now it has me wondering a lot.

If that's the case, do I possibly have a boost leak?

Is a leak at the charge pipes considered a boost leak, or is it just if the turbo can't hold a preset pressure, that's a boost leak? My terminology is trash.

I just want to ensure that the entire path going into the manifold is happy.

And other than working my way along every single piping/clamp between my IE intake, turbo inlet pipe, charge pipes, intercooler connections, and so on, is there a way to ensure I don't have any leaks going into the intake manifold?

In other words, I'm checking for boost leaks but I don't know where to start, at the turbo, at charge pipes etc. I've heard of smoke tests but not sure if that's what I should be doing.

Also, any tests that I can try with AP data to let me know if I have a boost issue just in general? Looking at boost and AFR I think are the obvious parameters but not sure what to look for exactly.

Any thoughts or theories about this MAP sensor thing I mentioned or on order of operations to try here would be appreciated.
 
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swcrow

Autocross Champion
Location
Virginia
Car(s)
7.5 GTI
Am I on the right path here?

Basically, I've noticed that unplugging and replugging in my MAP sensor has done wonders for fixing a lot of weird behavior on my car, but now it has me wondering a lot.

If that's the case, do I possibly have a boost leak?

Is a leak at the charge pipes considered a boost leak, or is it just if the turbo can't hold a preset pressure, that's a boost leak? My terminology is trash.

I just want to ensure that the entire path going into the manifold is happy.

And other than working my way along every single piping/clamp between my IE intake, turbo inlet pipe, charge pipes, intercooler connections, and so on, is there a way to ensure I don't have any leaks going into the intake manifold?

In other words, I'm checking for boost leaks but I don't know where to start, at the turbo, at charge pipes etc. I've heard of smoke tests but not sure if that's what I should be doing.

Also, any tests that I can try with AP data to let me know if I have a boost issue just in general? Looking at boost and AFR I think are the obvious parameters but not sure what to look for exactly.

Any thoughts on order of operations to try here would be appreciated.
Drew has a point.....are you making the boost you're supposed to be making?

Get a smoke test done.....that will show leaks....it's how I found my external wastegate was bad on my WRX.
 

SmoothCat565

Go Kart Newbie
Location
Massachusetts
Car(s)
2017 VW MKVII GTI
After about 8-9 days since I unplugged and replugged the MAP sensor, the car started to “break up” again today for the first time. I just unplugged the MAP sensor and replugged it again, and now the car drives smooth again. What could this be?
 

SmoothCat565

Go Kart Newbie
Location
Massachusetts
Car(s)
2017 VW MKVII GTI
OBD11 values for 4th gear WOT
Charge air pressure specified: 2.9 bar
Charge air pressure actual: 2.9 bar

These look like absolute pressures so gauge pressure is 1.9 bar = 28 psi which matches my accesport boost reading of 28 psi. Accesport doesn’t have the target value I guess. And OBD11 isn’t allowing logging for some reason, only live data. If you know how to log data to csv on obd11 let me know, it has more options of monitors to log compared to the AP.

So as long as those values are normal, I doubt I have a boost leak now which is good to know. Just a very very weird problem that causes excessive rocking and jerkiness when on and off throttle at low speeds that gets temporarily “fixed” when I mess with the MAP sensor or throttle body/position sensor. There’s no boost in those low speed driving conditions, so it’s probably not boost related. Honestly probably is my dogbone bushing but no shop wants to touch it so, here we are. Might try pulling my PUT sensor next time I get a chance
 

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Bcastine

Passed Driver's Ed
Location
New Hampshire
My PUT sensor on my 2015 failed, certainly caused bucking. Gave codes for throttle body and throttle pedal and for the 5V circuit. Made the car undrivable. I only figured it out because I inspected every senor on the 5v circuit and found some corrosion on the pins of the put sensor. I believe being low and close to the ground in time causes this sensor to fail.
 

SmoothCat565

Go Kart Newbie
Location
Massachusetts
Car(s)
2017 VW MKVII GTI
PUT sensor looked fine no corrosion, I guess my belly pan saved it in that regard.

Unplugged and replugged it and car magically started driving so much more smoothly.

Similar effect as when I did the same thing on the MAP sensor.

Will see how long it lasts before it probably goes back to weird behavior described above.

I think it’s maybe tied into an AFR related think I just have a gut feeling those numbers are probably changing as the car learns and unlearns as I mess with the sensors.

Or it might be TPS values, or something else. Whatever it is, def feel like the car is adjusting/compensating, and that brings the issue back.

Will see how it goes.
 

SmoothCat565

Go Kart Newbie
Location
Massachusetts
Car(s)
2017 VW MKVII GTI
Here is a data zap file of the bucking in 1st gear
1st gear bucking

The bucking happened only in certain zones of that data file. It happened when accel pedal position goes from X to zero, but only in the sections when AFR is approx 12-13.5, not in sections where AFR is at 29 ish....so if I let off the gas and AFR is at 29, there's no bucking, but if I let off the gas and AFR is in the 12-13.5 range, that's when bucking happens (for 1st gear, it bucks at lower rpms letting off with AFR at 12-13.5 ish which is in that last third of the data file....but if i bring the rpms higher then let off then there's no bucking and AFR is at 29, which is the first 2/3 of the data file)
 
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