Boost Pressure Sensor Location

I wanted to see if someone would take a look at this chart and see what they think the issue may be. Symptoms described earlier in this thread. (ie. On acceleration (hot or cold outside, hot worse) turbo lacks power and doesn't accelerate.


over boost??? Thinking it could be the usual suspects... N75, Vent Actuator, Dirty Turbo (Seems to run fine once up to speed, I do feel sputter in acceleration), maybe even vac lines.

Prior to this test, I drove the vehicle with a disconnected MAF sensor connector and it seemed to make no difference.

Any help is greatly appreciated.

Here is the zip tie on the actuator. It sits on the top of the turbo next to the firewall. With my fat hands, it is nearly impossible to get the zip ties in place.

Just did a test view on the actuator when turning on the key. Didn't move. When car is started, actuator seems to move in and out slowly, then opens all the way down, but seems slow. Will try zip ties tomorrow.

Note: This isn't my image. I borrowed it from Jnitrofish in
http://forums.tdiclub.com/showthread.php?t=318414

Im surprised no one else chimed in, after my description of the event.

As for your graph, I would take some time and isolate each run that you make, and make separate graphs so you can more clearly see what is happening on each pedal stomp.

Another thing is, I would try not to vary the pedal any while doing your logging run. Find a quiet highway, get into a higher gear you feel safe in, and get as long of a run as you can while logging. Maybe even a steep long hill. Then you would be able to see what it is trying to do after the boost spike. go from foot off the pedal, to pedal to the floor and hold it until your RPM or your speed is too high. Then Graph it.

As for what your graph is showing, and i'm far from an expert, but it looks like the "normal" boost spike that most PD people talk about. Computer requests boost, Turbo Builds boost, Turbo Boost overshoots, computer compensates, turbo under shoots, computer compensates, and it finally balances out. You can see that on your most recent graph. When your boost ends up higher than the requested, the requested drops, it comes down, and then it will eventually balance out where it should be.

Unfortunately, this seems to be the most difficult thing to diagnose. That, and there doesn't seem to be a solution. No one can figure out what is really wrong.

I think that some of the custom Tuners are able to minimize it a bit with a new map, but that's going onto a whole different path.

Good Luck, and hopefully the zip tie gives you the result your looking for

Andy

Thanks for your answer Andy. I talked to a svc mgr at VW in Albuquerque and he said to check the cam. Had my mechanic pull the cover and said the cam was shot.

I talked to VW Customer Service and of course they know nothing of the sort for the 1.9 TDI. Gas they admit, but not on Diesel.

I am pretty fed up with VW and may either trade it in as is (really won't run anymore) or fix it and get out of it as fast as possible. This car is too expensive to own. The gas mileage is nice, but the cost to fix or repair it far exceeds the savings in fuel costs.

In case anyone comes along and finds this thread and wonders what happened. Here is a summary:
1. Cam was shot
2. Replace the cam and the tappets with an aftermarket kit
3. Car still ran like ^#$%^&*( after doing this.
4. Took it to Dealership and they messed with it and couldn't figure out the problem.
5. They wanted to replace the heads for $7100
6. Vehicle was traded in for something that is cheaper to own.

So long VW's. It was great while it ran. Dealership said that VW had problems with this motor and the mfg recommended replacing the heads as well as the cam, tappets, etc.

We loved it while it ran, but this was ridiculous. Started having problems at 80K miles.

Shame you could not have gotten it to a professional in the first place.

Oh well, good luck.

These stories are so sad..

aai2on said:

Click to expand...

To all those reading this..you cant just grab a graph and post it. You have to graph ONE "wide open throttle pull". Meaning put it in 2nd or 3rd and floor it. Let the graph record till boost is maxed out then back out of the throttle, then freeze the graph and save it. Oh, and you should set pixel shift to its max setting for the most detail.

This graph is "crammed" all together. This shows no detail. one "pull" with pixel shift set at 15 is better to analaize.

The other graph that was posted has too much info making the details fuzzy. The more data pids you display the slower the scan tool runs. So to start with you should just graph rpm, requested boost and actual boost.

Below is a much better representation of what is happening on ONE wide open throttle pull. It would be better if EGR percentage was turned off and pixel shift was set to max though.

tdicharlie

What are the signs of a bad boost sensor? If I rev my car to high it looses most of its power until I turn it off and back on. I was told it's the boost sensor. Thanks

scan for trouble codes.

What you have is not the sign of a bad boost sensor. its the sign of a boost trouble code (probably)

This thread is done. Absolutely staggering - SHOTGUN APPROACH WITH IMPROPER DIAGNOSTIC EQUIPMENT DOES NOT WORK!

Glad you got rid of the car and into something more suitable.