6.0 Turbo cycling/surging
Well here's the latest problem with my 2004.5 F350 - 6.0 and some history-
For this project I had the truck apart for the better part of a month, only able to work on it a little here and there. Heads were decked .006", magnafluxed and pressure checked by a reputable shop, I put in new Ford head gaskets, ARP studs, Cam Position Sensor, Crank position sensor, #2 injector, o-ring kits for the rest of the injectors, new exhaust manifolds &gaskets, EBP tube and fitting, stand pipes, dummy plugs, 2005 intake elbow(removed throttle body assembly), gutted cat, and removed muffler, Pyrometer, 0-100 psi fuel pressure gauge, 0-30 psi fuel pressure gauge being used to monitor coolant pressure, Sinister coolant filter.
Previously(within the last year) - Oil cooler, welded freeze plugs into EGR cooler, HPOP, IPR valve, ICP sensor and pigtail, water pump, fuel pressure blue spring upgrade, 215amp alternator from 2000 E350 ambulance package, bigger cables to the batts, new batts, FICM resoldered, updated turbo oil drain.
So here's the problem. The truck ran great before this last tear-down, except that it was continually burping coolant from the degas bottle. Now that it is back together, the engine itself runs fine, but the turbo is constantly cycling. It's barely noticeable at idle, and while at a steady cruising speed. You can still hear it in the exhaust, but can't feel it. However, it is VERY noticeable on mid to heavy acceleration. WOT is better once it down shifts, but it is still there. I have removed the turbo twice to clean the veins and unison ring. They were good when I pulled it apart the first time, but cleaned them anyway. I took it off a second time today, just to double check, and double check all my exhaust connections for leaks. Everything mated up good and was not leaking. I pulled the VGT solenoid and checked the orings - all looked good. If I unplug the EBP sensor, the turbo smoothes right out, but then my boost is too high and I get "turbo fart" when I let off the pedal too quick. So I replaced my EBP sensor - no change.
One question I do have is EGR valve related. My EGR valve is still in place, and plugged in. Are the o-rings necessary anymore? It doesn't seem like they could affect anything since the cooler is blocked(I actually pressure checked the cooler to 60 psi while I had it apart again just to check my welds, then still made a block off plate to go between the cooler and the intake manifold just in case a leak developed someday. A bit redundant, but better safe than sorry.) I did notice today that somehow I have no gasket between the EGR valve and intake, so tomorrow I will take care of that regardless. I'm sure there is some air leakage there, but doubt it is enough to cause this. I've read just about every forum post I could find about turbo surging and I am stumped.
So other than cleaning the turbo or replacing the EBP sensor, any ideas where to go next? One other thing worth noting, I can see the EBP and VGT% reading fluctuate on the Scangauge, but it seems like the SG is reading very slow in comparison to the rate of cycling. It just seems that it updates very slowly - so it doesn't seem as accurate as it could be. Is there any fix for that? Thanks for any help, and I'd be glad to give more info if I forgot something that would be helpful.
Which also reminds me, there are no DTC's either, 165000 mi, Rotella T6 5-40, CAT ELC coolant.
Oh yeah, any chance removing the throttle body has anything to do with it? I've had the butterfly out since I originally blocked the EGR cooler, but always had it plugged in. Thanks again, Chris
Last edited by ckostac; 04-16-2014 at 06:18 AM.