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· Registered
8 Posts
Discussion Starter · #1 ·
I have an 05 F250 with 6.0 Powerstroke ( 275,000 miles) with a Scan Gauge II X Gauge and PIDS loaded into it.
I am experiencing a problem that I think isTurbo related. The truck starts and idles fine but when I start down the road it has a "miss" similar to the "miss" you get with a bad injector on a cold morning- which usually clears up when the oil temp gets up to normal.Only this "Miss" does not clear up when getting to operating temp.

When I floor the accelerator the turbo boost gauge on the dash goes nuts ( level highway-no load) It will shoot over to 35 psi and the truck will pretty much do nothing- then the Boost PSI will drop down to 10 psi and it will jump like it has power again ( but still has that slight jerky "miss") The turbo gauge on dash has never gone above 20 psi normally even pulling a 5th wheel uphill fully loaded.

Now going down the road empty it will show 10 psi boost when it used to barely move- then when I reach 70 mph empty I often see 20 psi on the boost gauge. The tach gets to jumping around- the boost gauge is flying all over the place and still no real power- just a jerky miss and some acceleration.

The high boost psi and lack of power really made me believe I had a stopped up catylatic I hooked up the Scan Gauge II and did some checking. My Exhaust Back Pressure seems to operate in the normal ranges so to me I am thinking that rules out a plugged catylatic converter ( Is this a correct assumption?)

Also with Scan Gauge II hooked up I see the readout for the Boost (BST) is actually quite a bit higher than what the dash gauge shows! Flooring it at 70 mph I see the boost psi on the scan gauge reaching 43 psi! I am not sure which gauge to trust because the Scan gauge also reads 13 psi boost with the engine off?

3 months ago I had to change out the up-pipe and y-pipe because of rotted bellows. While I had the turbo out I took it apart and polished everything ( it was replace by ford 3 years ago) really it was not coked up at all- just a thin film of soot on the parts. I also pulled the tube coming from the drivers side exhaust manifold that has a sensor on top- thinking it might be full of carbon. It was completely clean as well as the senors so I reassembled everything and the truck ran better than ever- proper boost psi, plenty of power etc... and has run like that for 3 months until now.

Still trying to troubleshoot-yesterday i puled to the shoulder and unplugged the wire to the turbo- then drove it. Had the obvious lack of power with no turbo but I was slowly able to reach 70 MPH. With the Turbo unplugged there was NO MISS that I had been experiencing when it was plugged in...making me think the issue is likely turbo related with the vanes stuck causing so much boost. Really having trouble accepting this because I know its completely clean in there and I inspected all parts while cleaning and could find ZERO wear.

So now my troubleshooting has led me to thinking the problem may be my VGT Solenoid. The Scan Gauge II shows the percentage open on it to be pretty much normal during idle and acceleration etc.. I understand that the reading I am seeing for this on the Scan gauge II is actually what the computer is "Telling" the VGT to operate at, but that does not mean the VGT is actually functioning properly.

I have no error codes during any of this and I hate to start throwing parts at it, but yesterday I ordered another VGT solenoid to try. Should be here in a few days. If that does not fix then my next step is to order a rebuild kit for my turbo. I REALLY dont want to do this if I dont have to. I REALLY don think my turbo plugged up from being shiny/clean in 3 months to dysfunctional.

Have you ever experienced this before where your turbo psi was way too high and trucked missed and lacked power- and maybe tell me how you diagnosed and fixed it?

Thank you

· Registered
60 Posts
Did you ever find out anything on this issue? I have started having a very similar issue, very high boost, pushing the 20lb red line but just no power, if I let off the accelerator and let the boost drop down some the engine seems to recover, but then pushing down again seems to kill any power that I gained.

Like you it also seems to occur with a cold engine but I never used to have this problem.
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