Another overboost problem
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Another overboost problem
This problem has been discussed thoroughly, but I can't find anything related to my specific problem. Just bought f350 06 with 80,000 miles. Had new oil cooler at 50,000. Truck is over boosting when loaded and if I really push it uphill unloaded. 75 mph, almost 3000 rpm and just won't change into last gear. Had turbo cleaned. Got better Vgt % on scanguage but didn't fix problem. New FICM... Didn't help. Just don't know where to go next. No mods or programs. Thanks in advance for any help.
Hotshot
Joined: Jul 2005
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From: Middle Tn.
This problem has been discussed thoroughly, but I can't find anything related to my specific problem. Just bought f350 06 with 80,000 miles. Had new oil cooler at 50,000. Truck is over boosting when loaded and if I really push it uphill unloaded. 75 mph, almost 3000 rpm and just won't change into last gear. Had turbo cleaned. Got better Vgt % on scanguage but didn't fix problem. New FICM... Didn't help. Just don't know where to go next. No mods or programs. Thanks in advance for any help.
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Thought about replacing turbo. Just hate to throw a thousand dollar bill at the problem without more than a hunch. Was hoping there could be something simpler to check first. One thing that might help is if I knew what VGT% should be pulling 7500 lbs uphill with WOT? I'm showing about 40%. Don't know if this is normal.
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No tuner. It will shift if I let up. But if I don't it will overboost. This never happened on the other 6.0 I had. Doesn't seem normal and is very frustrating to have to look at boost guage all the time to make sure I don't go into limp mode.
Posting Guru
Joined: Jun 2012
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It sounds like classic turbo stuck to me, it's exactly what I had a few weeks ago. If the vanes can't move smoothly through their entire range and the VGT solenoid isn't working properly it can't close the turbo to control the boost and you get over-boost. Just cleaning the turbo isn't always enough, sometimes the solenoid can fail too.
Brian
Brian
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that's definitely a possibility. My mechanic hooked the truck up to a computer and was able to cycle the turbo through all ranges. Unless the computer is reading something false, it seems the turbo is performing as it should. My head is starting to hurt from trying to figure this out. I also think I am showing way too much boost at low speeds with no load. Accelerating from 15mph to 35 mph in town, I'm showing 10 to 15 psi boost. I think this is too high. Thoughts?
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Hotshot
Joined: Jul 2005
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From: Middle Tn.
that's definitely a possibility. My mechanic hooked the truck up to a computer and was able to cycle the turbo through all ranges. Unless the computer is reading something false, it seems the turbo is performing as it should. My head is starting to hurt from trying to figure this out. I also think I am showing way too much boost at low speeds with no load. Accelerating from 15mph to 35 mph in town, I'm showing 10 to 15 psi boost. I think this is too high. Thoughts?
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That's true. But I have a 6.0 at work and did a comparison and mine boosted much higher than work truck. Maybe I'll just start replacing stuff. I need my truck running right. Leaving for 1000 mile camping trip in two weeks, and really want it right when I head out.
Token Redneck
Joined: Jun 2007
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From: Breckenridge, TX
Is the similar to the test that was done?
https://www.ford-trucks.com/forums/1...l#post10518111
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Not sure how he tested it. All I know is he did it on a laptop. I can definitely hear the turbo spooling when I drive it. Just don't understand which component on the engine would control when shifting should occur in relation to rpm and boost. There are probably several. I will probably replace the selenoid and see what happens. I just hate replacing parts without a good diagnosis. It gets expensive and aggregating fast. But, perhaps there is no other choice. Thanks to all for the insight.
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How high are your EGT's during overboost? Is it shifting during WOT or do you have to let off for it to go? Check your EBP sensor, might need a cleaning. Drive with the EBP sensor unplugged first and see if there is a difference (especially during WOT). I had a similar issue. Fixed with EBP, never had any codes.
Freshman User
Joined: Aug 2012
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From: Sioux Falls SD
well I have run in to at my work with semi that the vgt well work great when the engine is cold or warm but when hot form pulling they well stick super common on older isx Cummins and all Volvos with vgt just saying and its a well knowing issue with 6.0s
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Don't have EGT guage. It's always during WOT. Just won't shift from 5-6 no matter what the rpm. Let off and it shifts. Will definitely check EBP sensor as I have heard from several that it is a good place to check. It also stutters when you go from flat ground to graded slope as I increase throttle and rpm's. If you give it full throttle or let off it stops. Not sure if two problems are related or separate. Thought i would tackle overboost first and see if it helps.
Fleet Mechanic
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From: Tuscaloosa, AL
I pull a 8300 lb TT and running 70 mph up hills pushing a 98% demand and it will shift down. Well, it doesn't really shift down, the torque converter doesn't lock and it seams like it shifts down.
I imagine if I was at WOT it would do the same thing at 75 mpg depending on how steep the hill is. You push a ton of wind out of the way with the truck and TT combined.
However, my boost goes negative with no drop off in performance. Obviously I've got a sensor that is squirrely in the right conditions. The intake pressure drops to 0.7 to 2.0 when this happens. Me thinks I've got an intake pressure sensor issue. I don't have a clue if that kills my performance or not. Have nothing to compare it to.
I imagine if I was at WOT it would do the same thing at 75 mpg depending on how steep the hill is. You push a ton of wind out of the way with the truck and TT combined.
However, my boost goes negative with no drop off in performance. Obviously I've got a sensor that is squirrely in the right conditions. The intake pressure drops to 0.7 to 2.0 when this happens. Me thinks I've got an intake pressure sensor issue. I don't have a clue if that kills my performance or not. Have nothing to compare it to.
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