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Old 09-13-2019, 05:28 PM   #1
Join Date: Jun 2016
Location: Boise, ID
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Default Turbo surging/cycling

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?
JHays is offline   Reply With Quote

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