Still loosing power

OK, we are at our wits end!! There has been an on going deterioration of power over the past couple of years with our 2001 TDI. It has been in the shop, (Aaron's Autowerks of Phoenix Oregon) more than several times and we have spent literally thousands of dollars to no avail. Today we returned from a road trip where it accelerates well up to around 2500 RPM but then bogs down. We are just creeping over the hills at 45 MPH and shifting down where before just leaving it in fifth gear and cruise control would have sufficed. No CEL. Items that have been changed:

N75 and N18 valves
vacuum hoses
MAF
Turbocharger
Fuel Filter
Fuel injection timing adjusted


Shop says:

Compression is good
Intake manifold is not clogged
Injectors checked and good
catalytic converter is not clogged
Fuel tank pickup clear

Any other helpful suggestions would be greatly appreciated!

Bill

Are you 100% sure the vacuum pump is good? Generally speaking, if there is a lack of vacuum the the engine will still pull to 2500 RPM or so, and then fall on it's face. You might also check fuse #34.

Do you how they actually check the intake manifold ?
Did the take off the EGR & look inside?


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Nevada_TDI said:

Are you 100% sure the vacuum pump is good? Generally speaking, if there is a lack of vacuum the the engine will still pull to 2500 RPM or so, and then fall on it's face. You might also check fuse #34.

Click to expand...

Not having a vacuum gauge but when I pull a vacuum hose there appears to be good suction.
Fuse 34 OK
Intake manifold removed, cleaned, reinstalled


Thanks!


Bill

Will a dying MAP sensor cause a CEL? 2500 is right about where you'd be making good boost.

Get a gauge on the vacuum system. Just because it seems good, doesn't mean it's enough. A healthy vacuum pump should be able to build at least 20inhg quickly. If it's any less, the turbo won't work right, as max actuation on the turbo is about 18inhg.

Map sensors don't typically go bad either. They do, but not likely. Have you also checked for boost leaks? The side mounted intercooler likes to make friends with parking blocks.

OK. I hooked in my brake bleeder, vacuum tester and it bottoms out the gauge below 30 right off the pump. Disconnecting the hose at the vacuum reservoir and I am reading 23.


Bill

Alrighty, Nero Morg, it appears that you may be actually on to something. While checking for vacuum I automatically went through and was just checking connections. Today coming to work I have a pass to cross and the car appeared to climb it more easily, (hopefully not just wishful thinking?), so a vacuum leak may be the culprit.................... Thanks bunches! Bill

wjfyfe said:

Alrighty, Nero Morg, it appears that you may be actually on to something. While checking for vacuum I automatically went through and was just checking connections. Today coming to work I have a pass to cross and the car appeared to climb it more easily, (hopefully not just wishful thinking?), so a vacuum leak may be the culprit.................... Thanks bunches! Bill

Click to expand...

The nipple on the vac pump tends to become loose over the years and cause a vac leak when it wiggles. You can easily patch it with RTV or JB weld.

Another thing you could check, is vacuum to the inlet of the N75 valve to make sure it's getting at least 20inhg. Good vac at pump doesn't mean the rest of the system is OK. Also make sure your yin yang check valve isn't plugged, and orientated the right way.

wjfyfe said:

Today we returned from a road trip where it accelerates well up to around 2500 RPM but then bogs down. We are just creeping over the hills at 45 MPH and shifting down where before just leaving it in fifth gear and cruise control would have sufficed. No CEL.

Click to expand...

I wonder if you are getting limp mode?
Does the power suddenly drop or gradually?

You should monitor the vacuum while driving up the hill.
Get a piece of vacuum hose long enough to reach into the car.

Logging with VCDS should show how the boost and air flow are.

super1 said:

Do you how they actually check the intake manifold ?
Did the take off the EGR & look inside?


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Click to expand...

You can usually see the top portion of the intake manifold through the EGR. You cannot see the ports to the engine, but generally if the top is clean that means it has been cleaned and the bottom would be similar looking

Or take a drive up to Portland
http://forums.tdiclub.com/member.php?u=5182
OldPoopie can fix it. Seems like AAron just threw parts and money at it. These cars are simple, but they are different.
Could just be some bad wiring, very hard to find, especially with no code.

Just manipulating the vacuum lines noticeably, but temporarily, helped with the power, seemingly to indicate a partial vacuum blockage/leak. I will dive into it a lil more earnestly over the weekend and see if I can find a difinitive culprit.



Thanks for the direction pointing so far!


Bill

wjfyfe said:

Just manipulating the vacuum lines noticeably, but temporarily, helped with the power, seemingly to indicate a partial vacuum blockage/leak. I will dive into it a lil more earnestly over the weekend and see if I can find a difinitive culprit.

Click to expand...

The 1 way valve has been known to have problems.
I would measure the vacuum going to the top of the N75 valve and wiggle the hoses.

You should have at least 20 inches vacuum for the actuator to fully pull the arm on the turbo.

Wiggle the hoses and see if the vacuum drops.

If the hoses all look original it may be time to replace them. 1 at a time.
Your disturbing them may cause others to crack.

All the hoses and the one way valve have been previously replaced, with the exception of the main line to the brakes, which is currently on order, (upon closer inspection there are notable cracks.) But, we may have introduced our own problem if we have replaced something that, though new, may be faulty. Thanks for the additional ideas!



Bill

OK, I purchased a vacuum gauge and T'd it up between the N-75 valve and turbo. I really do not know what I am watching for, but the vacuum reads 18 inches at idle. Just cruising down the road it runs lower, Approximately 11, then when I accelerate it immediately jumps up to 18 inches and then falls wandering between 14-16 inches. Does this tell somebody something?



Bill

wjfyfe, you have 30" of vacuum at the pump, great! Let's try to figure out where it goes. Here is what happened to me some time ago: basically what you are going through and I was stumped also. Here is what I did: I checked the amount of vacuum at the input of every vacuum controlled device in the loop and I had "good" vacuum near the vac pump, but almost none at the anti-shudder valve on the other side of the engine bay. That info told me I had leaks in the system causing a lack of vacuum all the way across the engine bay.

Check the vacuum at the anti-shudder valve, and if it is less than 28" or so, you may be on your way to isolating the problem. In theory you should have the same amount of vacuum at the a/s valve as you do at the N75.

It does not appear you have VCDS, so the next thing I say to do will cause CEL's, not power robbing CEL's, but CEL's just the same. You can get them cleared for free at Auto Zone, or almost any other auto parts store. What I want you to do is to isolate the N75 and the turbo, you will be taking the vacuum line off of the tee, going directly to the N75 from the vac pump, and then to the turbo. So this temporarily bypasses everything but just the turbo. There is the line from the vac pump to the N75, the line to the turbo, and the "relief" line that goes to the air box. If the turbo starts working normally again, you likely have some leaky solenoids in your vacuum system.
If you have no luck at this point either, you can email me at Yahoo your phone number and I will call you back.

The numbers in post 16 seem a bit off to me.

Take the top hose off the N75 and attach the vacuum gague to the hose.
Running you should have at least 20 inches vacuum for the actuator to fully pull.

Wiggle the hoses a bit to see if it holds vacuum or flucuates. Should hold steady.
Also wiggle the plastic hose to the brake booster. Known to crack where it's hard so see.

Put the hose back on the N75.
Try taking the lowest vacuum hose off of the N75 and go for another ride.
It's the vacuum release to control the actuator.
Any improvement check the hose path through a tee and to the bottom of the air filter box.
Also that the fitting at the air filter box is not clogged.

Thanks folks for all the suggestions but we have finally grown weary of the frustration of this issue where we are replacing the Jetta as our primary over-the road vehicle and just surrendering to using it as my commuter vehicle,(it still does that OK). It has been a fantastic vehicle which served us well for nearly two decades, but now since diesels are being pushed sadly aside, nobody seems to know what to do with it when things are starting to go somewhat wrong, we are being compelled to retire it for a vehicle more capable and trustworthy, but most unfortunately at the sacrifice of twice the fuel usage. It was fun and satisfying while it lasted.

Bill

We had given up on trying to find a solution to this issue and just decided to live with the problem of lack of power. The Jetta had been downgraded from our primary vehicle to a daily commuter and we purchased a new vehicle for our long distance travel needs, as well as to tow our trailer again.

But, recently, there has been a development where the Jetta has out of the blue regained some of it's power back. Why, we have no clue, where the only "change" I can think of has been the coming on of autumn with the associated temperature dropping. Would this only be coincidence or does someone think there may be something to it?

Thanks,

Bill

I went back and read Post #1, sad story, car in search of a proper mechanic. Sounds like either the N75 was full of junk or the actuator or turbo veins are froze.
There is a member works on TDIs in Portland, Justin Grow, aka Oldpoopie, seems to get high praise.
This one also on our list, very close-Aaron's Autowerks, 301 N. Phoenix Rd.

Thank-you. If you had kept reading you would have discovered that the N75 valve, turbocharger, along with a host of other components, had been replaced, repaired, or cleaned where we had spent thousands of dollars at Aaron's without their providing a solution.



Bill

Nobody has addressed the lower temps as being a possibility for the power increase, so I can assume that it is the consensus that this is only a coincidence?

Thanks,
Bill

Well, thanks anyways, for nearly 20 years our TDI Jetta has been the most dependable vehicle we have ever owned, it is kinda hard to get too upset when after nearly 400,000 miles of exemplary service that it comes down with an ailment that seems to be stumping everybody! We guess that it is just time to put it out to pasture to enjoy the easy life as my daily commuter.



Bill

Old thread, huh, where my last post was around a year and a half ago where we were getting ready just to dump the Jetta. Well, obviously we have kept the Jetta around and the saga still continues where another diesel specialty shop expressed confidence that they could correct the issue so we allowed them to take a crack at it. Unfortunately, their confidence was smashed after their keeping it 8 months, apparently lots of diagnostics, trial and error with the mechanic trading parts with his own TDI, , the intake was removed and cleaned, (again), as well as the catalytic converter being completely removed, we are still no closer to corralling this power issue. It's 30 miles from the shop and driving it home I reacquainted myself with the issue finding that as long as I am easy on the accelerator it comes up to speed slowly, but confidently, press that micrometer too far and it will start surging and bog down. That is until it has come up to speed at around 3,000 RPM where it picks up pep again. My wife following me says lots of black smoke. If anybody goes back through this thread they will find that about the only two things I can think of that have yet to be replaced are the throttle position sensor and the ECU, so which should be the next experiment, does anybody here have their opinion?

Bill

Almost sounds like bad turbo... Maybe time for a new shop. Wish I could take a crack at it.
If the turbo fins are damaged, it won't build boost well, or at all.

Well, the first shop already thought about that and installed a new turbo, no difference. Thanks for the reply.

Bill

I agree with the above posters...2500 RPM and loss of power is usually loss of vacuum.

You say fuse #34 is good, did you physically remove it and check? They have a habit of looking when not.
Have you checked the voltage going into the N75? Yes, I know it is PWM but check for voltage there at idle.
Next thing, put your vac gauge at the solenoid farthest from the vac pump and see if you have 22" at the passenger side.

A lil more info where if I am easy on the throttle it will accelerate fairly well, but if I push it just that millimeter too far it immediately starts to bog down, so it is a touchy feely game trying to keep it just on that edge, plus no power on the steeper hills.