Intermittent Loss of Power under load.

Ok, new to TDIcliub and love the info.

Recently purchased (June 2012), 1999 Jetta TDI Mk3 GLX (1998.10 Mfg)[312,000 km] and have replaced the Oil/Filter with 5w40 [Edit mistype 10w40] Castrol Syn, and Spin-On Oil Filter.

Intermittently get 3 symptoms and possible two problems.
P0506 (ROM checksum Error), and
P1550 (wastegate /pressure differential)

-and-

Intermittent will loose power, then blink CEL , but recover.

Recently, drained fuel/water filter/separator, and all kinds of black carbon deposits came out, threw out deposits, checked for water in fuel. Tighten everything back up, re-prime filter buy running on idel for 3-4 minutes.

Take road trip for test run, 1/2 hour drive , Highway country road driving (80 Km/h). get P1550 error again.

Notice frayed vacuum hose that leads to Air Intake cover (Air FILTER) to left of MAP(??) sensor on air intake after filter.

Replacement hose on order, but was unsure at what would cause the sudden loss of power for 1/2 second while under load, or accellerating with A/C on.

Usually Occurs around 1600 RPM, but not always.

any pointer(s) will be appreciated

I would be checking all vacuum lines methodically. There is a small one inside the ecu that can be replaced too.

The 10-40n syn oil isn't really ideal by the way. Search for oil recommendations and read up on it the lube forum here.

Use the search function for both these topics and go from there.

The ecu error is likely the hose inside the ecu that connects the hose from the boost to the map. Odd, but true. Also, the hose from the boost to the ecu could do the same thing.

Posted wrong oil grade

Yblocker said:

I would be checking all vacuum lines methodically. There is a small one inside the ecu that can be replaced too.

The 10-40n syn oil isn't really ideal by the way. Search for oil recommendations and read up on it the lube forum here.

Use the search function for both these topics and go from there.

Click to expand...

---
I posted the wrong Oil grade , actual grade is 5w40. Oops.

Intermittent loss of Power under Load [Resolved]

Finally eliminated all of the points that could be causing a vacuum leak in the turbo boost vacuum system.

By use of golf tees (yes simple works best), eliminated all of the external lines after the vacuum pump.

Eventually deduced it to a crack around the nipple where the rubber hose connected to the vacuum reservoir.

Replace old plastic deteriorated fitting with new plastic piece.

No more P1550s after stepping on the on-ramp.

Hopefully this will help someone else along the road.

Vacuum reservoir?

Vacuum Resevoir

Abacus said:

Vacuum reservoir?

Click to expand...

Yes, the softball sized black plastic sphere, AND having a short(er) hose connected to the fitting.

When the engine would tilt forward (a little bit) due to piston force acceleration, the hose would put additional strain agains the fitting.

Eventually, a small crack developed at the right angle of where the globe connects to the fitting. Elimination of the hose that fed the vacuum resevoir, and noting the fault no longer was happening, caused me to check the resevoir.

The Sphere is used to hold vacuum, for the amount of air that is removed from the boost actuator, when the N175 relay asks for more boost.

The N175 Relay performs a 0-100% range on time, by performing a pulse-width-modulation to the solenoid, that in turn goes to the actuator.

Ie ask for full boost = 100% vacuum to pull the actuator and turn the Variable-Nozzle Turbo to maximum.

When the engine no longer needs boost, then the N175 valve is opened to the air and then normal atmosphere is allowed to refresh the amount of air in the system.

This then reduces the boost, (and is the reason for the lag and the spike in the graphs from engines, as they are acellerated from idle to WOT.

I'm cornfused too. A MK3 with a spin on oil filter doesn't usually have a vacuum reservoir and N75 controls manifold pressure to the wastegate not vacuum on the VNT.

Yeah, I'm a little confused about what car we're actually talking about...

Steve

Terrific-In-Tahoma said:

The Sphere is used to hold vacuum, for the amount of air that is removed from the boost actuator, when the N175 relay asks for more boost.

Ie ask for full boost = 100% vacuum to pull the actuator and turn the Variable-Nozzle Turbo to maximum.

.

Click to expand...

Hold the phone here.

You need to clarify which car you're talking about since you've now referenced TWO different systems. The first is in your first post where you said:

Intermittently get 3 symptoms and possible two problems.
P0506 (ROM checksum Error), and
P1550 (wastegate /pressure differential)

Click to expand...

So is it a Mk3, a Mk4, or a Mk3 with a swapped on VNT?

low power on hills

Yblocker said:

I would be checking all vacuum lines methodically. There is a small one inside the ecu that can be replaced too.

The 10-40n syn oil isn't really ideal by the way. Search for oil recommendations and read up on it the lube forum here.

Use the search function for both these topics and go from there.

Click to expand...

been using 05 30 clerk at parts store recommended 10 40 syn could that cause the low power apricate any help

Power loss

Newbie. Have power loss always in 4th gear at 3k or over 3k rpm. Never the exact same just always in forth gear. I can feel the power loss but can't hear anything mechanically wrong. Vacuum leak? Speed Governor? Heat soaked turbo? What the **** is going on? First turbo vehicle. I'm slowly making my way through and replacing all weathered parts. Thanks in advance for the help. Jetta TDI has over 300k.

Search for "limp mode".

03wagon17 said:

been using 05 30 clerk at parts store recommended 10 40 syn could that cause the low power apricate any help

Click to expand...

Let me clarify your question.

You have been using a particular weight of oil, 5w30, in the crankcase. And it worked fine.

A clerk inside an auto parts store does a lookup on the make and model of your car, and suggests you go to 10w40.

You install the 10W40 ? and then you get low power intermittently or consistantly?

If it has low power when it is cold (just started up), that is where it is possible the oil is too thick to crank over and slows the start cycle.

However, once the engine gets to nominal running temperature, there should be no loss of power.

The 10w rating is for the winter time , at zero C (32 F) , and how slippery the oil will be at that temperature.

So, since conventional oil used to be rated 10W30 for gasoline cars, that gave good enough performnce with moderate temperatures.

Obviously, it is going to be region (mostly temperature) dependant, so you would not want to put summer weight oils in the crankcase in the winter time.

Check the owner's manual for your car, and see what the trusted GURU in your neighborhood suggests.

ON the off, chance that there is something specific with the full syn 10W40 oil I would suggest staying with what you know works.

The 40 weight is a lttle thicker (sticks to the sidewalls a little longer on the inside of the bore, and aids in cooling the piston rods.

But, you mention a loss of power, this is inconsistant with a change in oil weight. Depending on how badly the pistons are worn, and the ztate the bore is in, there should be very little change in operation by changing the weight of oil.

Hope this helps.

Abacus said:

So is it a Mk3, a Mk4, or a Mk3 with a swapped on VNT?

Click to expand...

It's a MK IV, apparently this post has fallen into the wrong area (MK III).

(Or I posted it in the wrong place).

Either way, the engine is a MK IV, with a VNT Turbo , and is driven by a vacuum actuator, that is modulated (controlled) by a N75 Solenoid (and by the ECU under command by the RPMs, amount of fuel delivered, the size of the nozzles, and the MAF mass air flow sensor, all summed in the ECU to give the proper fuel profile, depending on the amount of boost (2:1) to have in the intake stroke.

It is a 2001 MK IV that had a similar problem as the MK III (Blue) that had similar problems in 2012.

Perhaps I should have added the part about selling the MK III (Blue), and stepping up to a MK IV(Green) , with the same problem symptoms.

It seems that "Limp mode" is common to both variations, and continues to MK 7?? (whtever is in 2015s).