Turbo boost not occurring consistently

Hi, Sprinter crowd, my 2003 Freightliner Sprinter is having turbo boost issues. When I first start the Sprinter in the morning or even after shutting down the engine for 30 seconds, the Sprinter has plenty of torque and puts out a small amount of black smoke. After roughly 5 - 10 minutes of driving, the torque goes away, requiring me to floorboard the accelerator pedal to get even adequate acceleration, and the exhaust is black.

I took the heat shield off from above the turbo unit to see the actuator rod for the variable vane control, then started the engine from dead cold condition and watched the rod pull the vane lever downward roughly an inch from where it sat with the engine off. Then, off for a test drive. As described above, after a few minutes of driving, torque went south on me, so I jumped out and checked the vane actuator (with engine running) and it was up in the same position it was with engine not running. So, shut engine down for ~30 sec., restarted, looked at actuator rod, and saw it pulled downward. Then, while watching it, it popped up to the "off" position.

Any ideas what is causing this and how to fix it? I'm relatively new to Sprinters, having owned ours for about eight months now. I appreciate any and all help and look forward to being able to contribute the the Sprinter community here.

The black smoke impies a clogged EGR. When did you last take it off and clean it (common issue in 2002/2003 Sprinters; I clean mine once a year in the Spring). Do you have any splits in the Turbo hoses - that will cause this as well.

Cleaned EGR but turbo boost still interrmittent

Thanks for responding. Yes, I cleaned the EGR about two weeks ago, and the van ran the same after as before. I don't understand why the boost is there for the first few minutes the engine runs and then goes away completely. I have a friend who lives at the top of a very steep hill, roughly 20% grade he's estimated, and when I drove to pick him up a few weeks ago, the Sprinter was able to make it up the hill easily, this ~5 mins. after start from cold engine, but when I took him back home after about an hour on the Interstate, I had to floor the Sprinter and we barely made it up the hill, going 2-3 mph at most with lots of soot spewing forth.

I'm thinking a malfunctioning EGR wouldn't cause this, but again, I'm new to Sprinters.

Again, thanks for your help.

There are lots of turbo boost entries here. Please use the search function in the blue bar (above). Its most often a problem with the turbo hoses (they get leaky over time), or a sensor that has failed or gone out of spec. If you have the original turbo hoses - that would be my first guess as where to look (there are 5 of them on the 2002/2003 NAFTA models, but usually its the 4 after the turbo charger that tend to fail).

billnation,
The reason is that your engine management computer is sensing a hi boost or low boost (I'd vote for a leak and low boost) situation, and shutting your turbocharger off.
As suggested, check for a leak in the turbo hoses, at the joints in the hoses and then have someone with a Sprinter specific diagnostic tool check for an out of tolerance or malfunctioning sensors that could be shutting the turbo off.
Also check that your vacuum hoses are all intact and not leaking. Your 2003 has the vacuum powered turbo charger actuator (the
device that moves the turbo vane lever and linkage) and depends on good vacuum to operate correctly.
What RPM are you running when you are pulling up hills? If < 2400, you can do your Sprinter a huge favor and manually downshift to 4th gear and get the RPM up into the most powerful and economical range (~2600 to 3000 RPM).
You might consider getting a Scan Gauge II or similar performance monitoring gauge system so you can see what the MAP (Manifold Absolute Pressure)/BST (Turbo Boost in PSI) actually is, and when/how it goes away.
If it "pops" at some particular boost level, you have a hose or hose joint that is failing to hold the full boost pressure, and when it "pops" your engine management senses that the boost is too low for the current fueling rate and puts you into LHM (Limp Home Mode) which limits the performance.
Any time you see the black smoke (un burned fuel coming out the tailpipe) it would be best to stop, turn the engine off so everything resets, and then start it up and manually shift up to keep the RPM up in the > 2700-3000 RPM range to keep the % engine Load and turbo boost below the threshold where it "pops" and puts your Sprinter in LHM.
The turbo shutting down is not normal and is a direct clue that your engine management is shutting your engine down to LHM level so that you can't damage it by running with less than the correct balance between the fueling rate and turbo boost.
Also remember that MAP/turbo boost is NOT something that you (the driver) have any control over. It's totally managed by your engine management computer, and beyond using a Scan Gauge II or similar to keep the % Load, fueling rate, and boost at low enough levels to avoid the "pop" there is nothing you can do from the drivers seat to fix this issue.
Need to get it diagnosed and the hose/sensor that's causing this issue repaired so you engine can run normally.
Hope this helps,
Roger

Re: Cleaned EGR but turbo boost still interrmittent

billnation said:

I don't understand why the boost is there for the first few minutes the engine runs and then goes away completely.

Click to expand...

Simple: at some point the leak opens and the engine control unit (ECU) notices the loss of boost.
So it goes into a "safer" mode and stops even *trying* to get boost.

When you stop the engine, that clears that "temporary" fault status, and you get boost the next time you start it.
Until the leak happens again.

On my 2005 Sprinter, the leak only opened up enough for the ECU to notice it if i got up to 27 pis Manifold Absolute Pressure (MAP, one of the readings on a ScanGauge). Once i did, the turbo gave up and i was reduced to (roughly) normal atmospheric (15 psi).

--dick