Turbo surging/cycling


New member
2006 Freightliner badged Sprinter 3500
168,500 miles

Initial Problem:
Heading out for the weekend we got fuel, approximately 1/2 tank, at a Maverick station. Then drove through town to the interstate.
Once on the interstate at speeds around 65 mph I noticed a "surging", what felt like I was lifting off the gas pedal and then back on the gas despite pressure on the pedal being unchanged. This would happen regularly every several seconds while I was trying to maintain that speed. I pulled over to see if I could figure out what was going on, but didn't see anything readily causing the issue. I got back on the road on a highway and things seemed fine for a bit until I hit an uphill. Once I hit the uphill this "surging" became more pronounced and happened at lower speeds (40 - 50 mph). Additionally, if I punched the gas on a flat road there seemed to be hesitation in the gear changes from 3 to 4, running well past to 4,000 RPM before the shift which I never noticed happening before now. We pulled over again, this time I had coolant boiling out at the coolant fill cap. I also noticed several cracks in the upper intercooler hose where it hooks in at the top of the engine. I let things cool back down for a bit, then we turned around and went slowly back home. I never got any codes or check engine light.

So I did the following services:
- Intercooler to intake hose replaced (this had several cracks in the upper portion)
- EGR coolant hose replaced (this was brittle)
- Fuel Filter replaced (this needed to be done anyways)
- Turbo resonator (slightly cracked at seam, replaced with aluminum resonator from purchased from europarst-sd)
- Coolant added (Mercedes blue, matching what the vehicle had already)

Back on the road for a test, the surging/shift problems were still happening. After digging through the forum, I initially thought it might be the torque converter lock-up solenoid, conductor plate, or both and possibly a shift solenoid (also the cracked hoses).
So I did the following:
- Replace transmission conductor plate
- Replace torque converter lock up solenoid
- Replace shift solenoids (3 of them)
- Replace transmission electrical socket
- Replace transmission filter
- Replace transmission pan gasket
- Transmission fluid fill (Fuch Titan ATF 4134)

The old fluid looked pretty good, as did the filter when I cracked it open. It had only been about 5k since I last serviced it using Shell ATF 134.

Road test again, same problems. So I took it to the Mercedes dealer, they service Sprinters and I've had all good experiences with them. After several days they couldn't figure out the issue, no error codes and nothing came up in their diagnostics. So I spent some more time searching the web, this time I used the term "surging" and the results put me on the path of the intake. I mentioned this to the dealer and they took another look but still nothing definative. The dealer was going to order an EGR just to try a new one, but at this point I took the van back from them and figured I'd try a few things myself.

If I unplug the MAF, then I no longer get the surging from the turbo. The van is a bit gutless, but otherwise seems to run ok minus the turbo.

I tried:
- Check the air filter (previously replaced 5k ago)
- Vacummed and blew out the air filter
- Vacummed out crud in the air box
- Checked electrical connections to MAF and air pressure/temp sensors
- Tried to clean the MAF

Road test, same problems.
Next I tried:
- Clean the EGR (this was pretty caked up and did not return to closed freely when I opened it by hand until I cleaned it)

Road test, same problems.
- Replace intake air pressure sensor
- Replace intake air temp sensor
- Replace MAP sensor (pressure sensor)

Road test, same problems.
- Replace MAF

Road test, same problems.
- Replace EGR & gasket

Road test, same problems.

At this point I think the only thing left, aside from throwing cash directly at the van, might be the O2 sensor. Otherwise I'm pretty much out of ideas.
I'll spend the weekend going over hoses and electrical connections again just to see if something is cracked or abraded.
On the plus side, now I have a bunch of spare parts if I ever need them :)
I also just got a ScanGauge II, so I'll try to monitor pressures via that when the problem happens.

Anyone have any ideas on what I can do further to diagnose this?


Engineer In Residence
You need to get a scanner on it, and monitor the live data. There are numerous intermittent conditions that can cause this issue. One bizarre one is a bad oil temp sensor. Another is a sticking fuel quantity valve.

Any signs of pulsing or rough idle?

Have you checked the turbo actuator for the pulsing movement at idle?

What are you using to check codes? A sprinter specific scanner (not scanguage) is needed to view all the modules for pending/stored codes.

Other thoughts, Pedal sensor, check live data to make sure its consistent.
Exhaust or boost leak. Either one can open/close as the boost pressure changes, creating a hysteresis loop.
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New member
I did have it at the Mercedes dealership for several days where they ran it through their diagnostics, but no codes were found. They also weren't able to determine anything from live data, but I don't know to what extent they did live data monitoring. I have just the scangauge readily available to me, but figured if the dealer isn't coming up with anything then no surprise if my scangauge doesn't either.

Haven't detected any pulsing or roughness at idle. But my detection method was purely by feel.

Haven't check the turbo actuator, I'll give that a look today and check per https://sprinter-source.com/forum/showthread.php?t=16575

Thanks for the quick feedback, I'll give some of those ideas a run through.


New member
So yeah, definitely a leak in the upper charge air hose... :doh:

Not sure if the replacement hose that I ordered was supposed to have an o-ring included, but it definitely didn't come with one (and I installed it that way like an idiot).

$8 bucks later... should be fixed.


'02 2.7 T!N Freightliner
On my '02 I'm getting an oil leak at the a the upper charge air connection despite changing the O ring twice. It feels like a sloppy fit even with a new O ring. It's not excessive, just ugly.

I'm not sure what to do about it, it makes a mess below itself. I am running just fine but it makes me nervous. I could try a sealant but I hesitate.
The whole hose connection sort of hangs a little and it strikes me as a failed design?
I've taken to wrapping the joint with parer towel and tape to contain the black oil mess.

bill in tomahawk
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Patrick of M

2005 T1N 2500 (NA spec)
So yeah, definitely a leak in the upper charge air hose... :doh:

Not sure if the replacement hose that I ordered was supposed to have an o-ring included, but it definitely didn't come with one (and I installed it that way like an idiot).

$8 bucks later... should be fixed.
Well the good news is you have replaced so much, should be reliable rig now.
Btw I was going to suggest cracked/perforated intercooler , that would get you the surging as well.
What MWD said is correct you need a scanner that can read (and clear) the modules, there is a scanner section on this forum so check that out.
Live data while driving is very helpful, and should help avoid the “throwing new parts at it syndrome”.


If your coolant was boiling is it overheating? Limp mode happens without an engine light or codes when the coolant is too hot, the fuel is too hot or the oil temp is too hot. Could be a bad sensor or you could be actually overheating one of those fluids. Real time data when the problem happens will tell you.


2004 140” SHC U.S. T1N
Your description of symptoms sounded EXACTLY like my recent split intake hose, so your missing O-ring fits. I found a Low Boost code in the ECM and a 1-1/2” tear on the top of my upper intake hose.

Bill: have you considered a bit of shimming under the o-ring? A narrow strip of adhesive foil duct tape may stem the flow.



New member
Got an o-ring, it was actually floating loose in the box from my first parts order and I mistook it as an extra o-ring I ordered for something else. Then took the van for an extended test drive on some nearby hills with pretty good speeds (55 - 60 mph). No problems to report, all went well.

Temps stayed around 210 F on the high side while running up the hill for several miles. Then they came back down to about 180 F on the downhill. No boiling over of the coolant, though when it boiled over before the temp gauge was showing around the same temps. Just something to be aware of if anyone else has similar issues I guess, maybe I still had a bad temp sensor.

Bill, not sure if it helps but the o-ring I have is black, flat on the inside and double ridged on the outside. Not at all like the rounded orange or green replacement o-rings I was seeing in my searches and on the replacement hose pictures. An auto parts store nearby had a non-OEM replacement hose that I checked out, it had the same type of o-ring. If you are running a rounded o-ring, perhaps you can find an o-ring like I ended up with.

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