View Full Version : My weird loss of boost

05-18-2015, 09:50 PM
I posted before about a loss of boost pressure that seems to be sensor related. The turbo does not activate (sometimes) when I start up after letting the van sit a while, after having driven it. It does not lose boost as I'm driving, it just never activates. A quick re-start usually fixes it. It never does this when starting cold in the morning.

I was watching my Torque gauges today, and noticed when I started the engine the VDC dropped to 10.8 while cranking, and that start also resulted in no turbo. I re-started and the VDC only dropped to 12.2, and I had turbo. The charge when engine running is 14.4-5.

I'm starting to suspect it's the battery or connections, and when the VDC drops too low, it goes in to a type of LHM.

Does this sound plausible?

05-19-2015, 02:43 AM
Yes. I don't have specific measurements, but I have the same issue. It was more frequent prior to replacing my alternator and battery; approximately monthly prior to replacement and less than yearly after replacement. There is a post or two a from a few years back http://sprinter-source.com/forum/showthread.php?t=23364 that mentions a similar experience and I believe there is another that suggests a through cleaning of any ground connections.

05-19-2015, 03:00 AM
My alternator should be fine, I pump out 14.4vdc when the engine is on. The battery may be junk, I've had it for 2-3 years, and it is the #3 replacement for a series of prematurely failing Bosch batteries (first one a month, second one lasted less than a year, this one replaced it). I'll run out to Pep Boys and have them test this one, maybe I'll get another free or discounted replacement. Of course, I'll check all my ground connections first.

Having it show 10.8vdc while cranking sure seems low to me.

05-20-2015, 01:17 PM
Hi, Sounds like same problem I've started having. Although van runs fine when started up. can drive fine. accelerate with turbo cutting in fine. Then can be cruising along and hit the throttle and no reaction. Feels like there is no turbo.
Clutch in, turn ignition off and bumpstart or keystart and off it goes with full power again. Also seems to happen sometimes when trying to accelerate up a hill etc. but restart and it runs fine.
Did you get a fix for your issue?


05-20-2015, 02:57 PM
Dave, I haven't had time to mess with it yet. Maybe this weekend. I'm going to check the battery and the ground connections first. If yours is cutting while you're driving, it might be something different than mine. Mine is no boost from start, but restart usually corrects it, and it never cuts out while driving.

05-20-2015, 03:19 PM
Yeah, been reading through a few other posts with the same problem. Have a few things to try over the weekend. It's not noticeable when I'm cruising on the flat. Just if I start an incline it seems to have no turbo boost. Drops to around 40mph, Change down a gear and it still looses power. If I restart whilst I'm going along, then the turbo seems to kick back in again and accelerates as normal. Definately electrical if a "reboot" fixes it.
Cheers :)

05-20-2015, 05:35 PM
Could be something other than just electrical. When T1N turbo resonators have failed due to leakage of boost, thereby putting the vehicle in limp mode, often a restart will eliminate the limp for a period of time.

05-20-2015, 06:02 PM
Low voltage during cranking could result in odd conditions. Others may have more experience, but 10.6V is about the minimum I would want to see during cranking.

If you decide your issue is low voltage during the start process I would test as follows.

Using a digital volt meter with Max/min function. Place the probes on battery terminals. Crank/start the engine and note the minimum voltage. If it is 10.8 or similar, your battery is likely the fault. If not continue testing. The engine to frame ground strap, battery to frame ground strap and positive cable are the major items I would test. Repeat the process by placing the meters probes on both ends of these cables until you locate the source of the voltage drop.

On my van the engine to frame ground strap was dropping 1.2V during cranking!

05-21-2015, 02:23 AM
I went to Pep Boys, where I bought my battery, and had them test it. It came up as "replace battery" because it had 690 CCA and it's supposed to have 850 CCA. I thought I might be still on "free replacement" but I'm a few months over (figures). I kept my battery and will buy a better brand rather than another crappy Bosch.

While I had the battery out I twisted and scraped the ground connection to the chassis a little, and there was a little corrosion on the POS terminal, but not much. Thanks for the idea to test voltage at terminals and at chassis and compare, I'll do that. My OBD port probably gets voltage directly and not from a different sensor, and it showed 8.7vdc when I turned it over this morning! Here's the weird part: it didn't go into no-turbo mode with that startup, it never does in the morning, only after it's been driven, and sometimes it sits for 10 minutes or 3-4 hours, and it will go in to the no-turbo mode when I start it up, but a re-start fixes it.

05-21-2015, 02:47 AM
It's alive

05-22-2015, 12:44 AM
Thanks GaryJ something else to check at the weekend. I had a quick look and play with the connections on the air flow sensor today and the van was running like a dream. Drove about 20 miles on the motorway overtaking trucks etc. Same on the way back until I was around 65 mph, pulled out to overtake a truck, just as I got alongside the truck it did it again. So I had cars behind me and I couldn't get past the truck I had slowed enough to pull back behind the truck then onto the hard shoulder. Restarted and took off again and overtook the truck 2miles down the road and ran perfect all the way home. No strange noises or air leaks to be heard which is another reason I thought it may be electrical. Will strip down and have a better at the weekend.


05-22-2015, 01:16 AM
Could it be that the starter has a problem and is drawing too much current?

05-24-2015, 04:33 AM
I'm going to explore an entirely different source.
I was thinking of cause and effect, and I first noticed this issue in late January and early February; most noticeably on a trip to Mendocino the middle of February. I had thought it was a bad injector; a leak off test showed 1.5" on #2, and I replaced it but still had the issue. I remember hoping the new injector would arrive before we went to Mendocino.

The only "cause and effect" things I can recall are getting back from the holiday trip to Oregon and discovering loose tranny pan and dripping tranny fluid, and the plastic bag tearing up the seal on my differential.

I cannot recall adding any fluid to my transmission, but I'm sure I lost a noticeable amount. I checked it the other day (hot), and it showed too full! HOWEVER, I feel a little "bump" when using the dipstick before it stops, so I may be inserting it too far. I'm going to check the archives for the dipstick measurement. Yes, mine has the ears. If stopped at the "bump", it doesn't show fluid on the dipstick. The other day the turbo was operating, and I stopped at a traffic light which was on a hill, facing down, and when I went to take off, the turbo was not working. I don't get any warning lights on the dash, but it's possible I have low tranny fluid. I'm guessing that driving it on the freeway and then parking, the fluid is in the torque converter, and when I restart, the sensor thinks there isn't enough fluid and puts it in the LHM. The quick restart may start it fast enough that the sensor's signals are overlooked. Just a guess.

Differential fluid is fine, bolts are tight, no sensor there that I know of.

Leak off test last night was 1/8" to 0 on all 5. No apparent leaks in the charge air system. Some slight oil leak at the tube from the block to the turbo, probably could use a new seal but it looks pretty minimal, with some old build-up.

Going to explore the transmission more in the next few days.

05-24-2015, 04:52 AM
Google is a better way to search for stuff on the forum than the forum's search engine!
Found an old post by vic and others, 44.75" from the tip of dipstick to the end of the tube. I'll check tomorrow.
Also found some posts on this and other forums saying low tranny fluid can trigger LHM.

05-24-2015, 08:45 PM
Hi there,
Did you ever read and see if anything was stored code wise?
This sounds like a temperature related cam sensor (Crankshaft/camshaft synchronisation) error that resets without any warning lamp on ignition cycle.
Either temperature or rpm related problems in this department and the symptoms are not far off what I have experienced on more than a few occasions.


05-24-2015, 09:38 PM
Hi there,
Did you ever read and see if anything was stored code wise?
This sounds like a temperature related cam sensor (Crankshaft/camshaft synchronisation) error that resets without any warning lamp on ignition cycle.
Either temperature or rpm related problems in this department and the symptoms are not far off what I have experienced on more than a few occasions.


I don't have DAD or DRB3, and my apps show no stored codes. I checked the trans fluid level today and topped it off, haven't had the opportunity to see if that works yet. I'm thinking more of a fluid thing since it went to turbo-off mode while I was idling at a stoplight on downward facing hill the other day. It's never cut off when driving, at any speed or under any load, before. I have a spare CAM, and I can try that. I'm also thinking that I may be due for a new EGR, since this one has about 100k on it.

05-25-2015, 11:20 PM
I'm getting old, er.
I found a reference to an old thread from 2011 that I had contributed to, where I had the same exact problem I have now! I even started with the IAT and MAF sensors, and moved on to the vacuum actuator, as I am doing right now! It turned out to be the EGR. I'll take mine off and clean it again tonight and see what transpires. 155k on the original, and this one has 85k.

I tried a block-off test today and it didn't help, though.
I've also bypassed the vent control, and that didn't help.

05-26-2015, 02:01 AM
Cleaned the heck out of the EGR, blowing in the exhaust end did not result in air getting through unless I moved the arm. Still getting the boost reduction, and now it is happening every time I drive for 2-3 minutes. It's getting worse fast but has been happening for several months. A re-start does "clear" it, but it comes back while driving a few minutes now.

I checked all the vac lines, and they are holding pressure (out). One experiment I don't know what to make of: I plugged the vacuum line filter end, and had normal to slightly high boost but not the torque that I get when I re-start it; acceleration was still weak. MAF readings synched with the boost pressure as usual.

Earlier today I unplugged the vacuum actuator to see if it behaved the same as when it loses boost. I get up to 3-4psi when accelerating hard when in LHM, and wanted to see if that was just an effect of the increased RPM. Unplugged, it didn't get above 1psi, so I'm getting some boost when in LHM. It's odd that I get any at all, it seems like it should be all or nothing LHM. Normal function sees boost rise to 6-8 on easy acceleration, 16-19 on hard acceleration. In LHM, I might be able to get 4.5 if I floor it.

I'm stumped. Maybe it's the EGR, and the sensor is sending signals telling the ECU to cut power, but blocking off the exhaust port didn't have an effect.

05-26-2015, 06:41 AM
I would still suspect the vacuum solenoid. In my case, intermittent LHM without codes was solved when I sealed the ends of the solenoid with silicone sealant. Interestingly, my solenoid was new from the dealer less than 6 months previously. So, I have far less confidence that new parts are always perfectly functional.

05-26-2015, 10:32 AM
When I first got My sprinter the egr was bad already and like every diesel I have I put a set of gauges including turbo, it would boost up to 3psi or 4psi if I push the throttle hard. Mine would do this (disable the turbo) after a couple miles of driving, I know so bc I could first hear the turbo spool and after a couple minutes it was gone.

Aqua Puttana
05-26-2015, 10:48 AM
Watching boost pressures is helpful, but that is only giving you the end result.

Eric Experience always recommends a vacuum gauge on the system so you can actually see the operating pressures. Not only would I do that, I might make the gauge a permanent installation. It would be good to have a feel or history of what the normal operating vac pressures should be. That may help to notice a problem earlier on rather than after it actually sets LHM.

:2cents: vic

05-31-2015, 07:42 PM
I too am having loss of power issues. To determine if this is turbo related, I can easily install a pressure gauge on the manifold but I am unsure what normal pressures I should look for? I have a gauge on my Dodge Cummins and figure I could always look for similar pressures at various engine speeds but info from other good Sprinter guys would be best. Thanks in advance.

05-31-2015, 07:54 PM
Since there is no predrilled hole for a fitting on a Sprinters turbo system manifolds/hoses/sensor boxes, it would not be so easy
to install a pressure gauge.
You can read the Manifold Absolute Pressure (MAP) with any of several performance monitoring gauge packages.
It reads out electronically through the OBD-II port.
There is a MAP sensor in the turbo system as well as a MAF sensor, ambient air temperature sensor.
It's all done electronically!
Normal readings (at sea level altitude) are:
Idling....no turbo boost.... ~14.7 PSIA or 0 PSIG if you chose "boost" (BST) instead of MAP.
Normal Cruising....moderate turbo boost ....~29-30 PSIA MAP.......10-18 PSIG BST.
Full throttle.....full turbo boost... 35-36.9 PSIA MAP......20-21 PSIG BST.
You might be able to go to a local auto parts store and borrow their OBD-II device, go for a
short drive with it plugged into your Sprinter OBD-II port and find out if your MAP/Boost is normal
or not.
Hope this helps,

06-04-2015, 08:55 PM
New EGR came a while ago, I just finished putting it in. I had cleaned the old one about a week ago, and it was pretty gunked up in the exhaust port already. Something I noticed when I cleaned it and now is that there were granular chunks in it. They are not metal bits, I can crush them with my fingernails. They are carbonized chunks. It also oddly enough LOOKS like water mixed in by the way it flows, but it also is dark/black. I have no coolant loss and there is no other source for actual water-like fluid. I'll assume for a minute that it's the 0 part of the 0-40 oil.

Anyway, test drive in a bit to see if it clears up the issue of low boost.

Are the granular bits and watery fluid any sign of something more insidious? Too much oil coming in to the turbo?

06-04-2015, 10:54 PM
Test drive to pick up the kids, including a couple stops, highway driving and city driving; all resulted in ZERO loss of boost.

So, it looks like it was the EGR. But, I'll update after a week of driving around. Actually, I have to go up in to the Sierras next week, and then over to Mono Lake to scout for locations, so the van will have a real workout.

One thought; since I tried a block-off plate on the EGR and it had no effect, and it would hold air until I moved the cam when I blew into it, it wasn't a worn seal at the valve itself like my last one. It must have failed at the servo somehow. Either not achieving the proper position and the MAF data compared by the ECU didn't add up, putting it in partial LHM, or whatever sensor determines IF it is in the proper position failed. The last EGR only survived about 90k, so this is probably the last one I'll have to buy.

06-04-2015, 10:56 PM
knock on wood

06-16-2015, 05:17 AM
It was the EGR. :thumbup:

1000+ mile trip; up over Sonora Pass, down around Mono Lake, up and down a bunch of Jeep/UTV trails, back over Tioga Pass and home.

Absolutely zero problems.

If I still have my van 100,000 miles from now and post something about a periodic loss of boost that gets reset but eventually becomes permanent, refer me to this thread. :smirk:

OK, now I'm wondering WHAT it is about the 02-03 EGR that fails. This last one was holding air when the valve was closed, so boost was escaping elsewhere or the signal from the position sensor for the servo was whack.
I wonder if the part of the design that lets a little oil-soaked air into the arm chamber to lubricate it wears out and lets TOO MUCH oil-soaked air through? Thus the dripping EGR. If that's the case, it may be losing enough boost that the MAF and EGR signals don't jibe, and results in the ECU activating a LHM or partial LHM.
If this is indeed the cause of the failed 02-03 EGR, then it seams that replacing the seals at the valve arm, or whatever it is that is supposed to limit how much oil soaked air gets through, would "fix" it. I'll take a closer look at my old one. I recall seeing a scalloped part of the tube housing the valve arm, maybe that's where the oil-soaked boost air gets to the arm chamber. Perhaps a "failed" EGR can be brought back to life by partially or mostly blocking this scalloped area? :thinking:

06-17-2015, 02:10 AM
Yeah, been reading through a few other posts with the same problem. Have a few things to try over the weekend. It's not noticeable when I'm cruising on the flat. Just if I start an incline it seems to have no turbo boost. Drops to around 40mph, Change down a gear and it still looses power. If I restart whilst I'm going along, then the turbo seems to kick back in again and accelerates as normal. Definately electrical if a "reboot" fixes it.
Cheers :)

Addition: Engine light was on, and I'm a motorignoramus:
2012 Unity IB, towing Jeep Wrangler, just back after 4,500 mile trip, 33k miles on the vehicle: after leaving Canada we fueled up just at the border, I-29. Fueled again in Fargo ND. After this we lost boost on I-94. Closest MB service was over 100 miles back, in Fargo, which we were told would require a tow. (We were heading west.) Sprinter road assistance tech suggested turning off engine, opening door, closing door, starting engine, revving engine - a kind of re-boot. He thought it might have been "bad" diesel It worked for a while, then repeated, several times. No one would help us - no one had MB Sprinter software, not Freightliner ND. Used up most of the "bad" diesel, refueled, then next day had no problem - until a few blocks from home, heading up an incline, like Meikodel's post above. We'll have to take it to MB Sprinter service, an hour away (only a couple in Colorado, all on the Front Range). I was hoping to be prepared for the visit but the LHM posts seem to be all over the place regarding possible causes. I didn't see any mention of "bad" fuel. I so don't want to get ripped off at service, so if anyone has suggestions on what we should look for and tell service, I would be very grateful.
Also, I question my choice of MB Sprinter when there are so few service sites. Had a similar problem on the West Coast heading north: Needed regular 10k service and had to drive to Olympia to get it. Thanks, all. Sorry this was so long.