Idle and acceleration issues. - PowerStrokeNation : Ford Powerstroke Diesel Forum
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post #1 of 80 (permalink) Old 05-01-2017, 12:44 AM Thread Starter
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Idle and acceleration issues.

I've got this ongoing problem going on that came up after I fixed a no hot start issue, and figured I would start a seperate thread for this issue to try and get it finished off.

It started off as a slight stutter on acceleration, It was kind of random, mostly around 35mph, then also could notice it around a specific throttle position, kind of hard to pin down.

I ended up replacing the CPS with a blue one from RiffRaff, and it made no difference that I could tell.

Then the next day, I installed a new pedal positioning sensor, and it seems like that helped a lot, but its still there. Every so often while driving, Ill feel the truck shake and stutter, but not near as bad as before.

Then I put the Black CPS back in, thinking maybe it was causing a Cyldinder imbalance and making the truck shake. I also pulled the VSS sensor and cleaned it off and reinstalled it at the same time. Then went for a drive, and it was HORRIBLE. Noticed the speedo jumping around 55mph, it would jump from 40->62->50->45->65 etc etc. So i knew VSS was bad.

Installed a new VSS, and were back to square one with it happening every so often, a little shake/stutter, and a slightly rough idle. Enough to shake the truck and me in it, but still "sounds" smooth.

Has new HPOP, new IPR, new ICP, new VSS, new TPS, new CPS (tried both Black and Blue), all 8 injectors were tested, 3 turned up bad and were replaced a few months ago, so all 8 are acting as they should. Checking resistance at the 42pin plug on the fender well showed every injector between 3.8-4.0 ohms, so no wiring issues.

Any ideas guys?


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1996 Cali F350 CCFB, 7.3 PSD, 2wd SAS, w/ 380,000 miles.
New Motor at 352,000, DieselSite Legendary Trans at 356,000 and many more
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post #2 of 80 (permalink) Old 05-04-2017, 02:27 AM Thread Starter
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Re: Idle and acceleration issues.

Bump, any ideas anybody? Im stumped.


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1996 Cali F350 CCFB, 7.3 PSD, 2wd SAS, w/ 380,000 miles.
New Motor at 352,000, DieselSite Legendary Trans at 356,000 and many more
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post #3 of 80 (permalink) Old 05-04-2017, 04:06 AM
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Re: Idle and acceleration issues.

How old is the oil?
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post #4 of 80 (permalink) Old 05-04-2017, 04:29 AM Thread Starter
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Re: Idle and acceleration issues.

1500 miles, maybe less. I put in a new motor at 352,250, changed the oil at 352,600, now it just ticked 354,000.

Could the motor breaking in be leaving deposits of something and contaminating it? I have a brand new filter sitting in the box in my garage, maybe I should just change it?

What I do find odd about the oil is that its about the color of regular used gasoline engine motor oil, not BLACK like diesel oil is almost immediately. I chalked this up as it just being so new, the blow by hasnt been able to contaminate it enough?


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1996 Cali F350 CCFB, 7.3 PSD, 2wd SAS, w/ 380,000 miles.
New Motor at 352,000, DieselSite Legendary Trans at 356,000 and many more
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post #5 of 80 (permalink) Old 05-04-2017, 08:53 AM
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Re: Idle and acceleration issues.

One reason for the oil staying clean is a new engine would not have any soot accumulation. I would change it just to get rid of any foreign stuff that may be in a new engine.

The VSS harness may have a bad spot in the insulation causing an intermittent problem (like a ground).
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post #6 of 80 (permalink) Old 05-05-2017, 02:14 AM Thread Starter
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Re: Idle and acceleration issues.

So maybe I should start checking the VSS harness? Does the harness go anywhere that I cant see? Like in between the tank and frame?


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New Motor at 352,000, DieselSite Legendary Trans at 356,000 and many more
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post #7 of 80 (permalink) Old 05-05-2017, 01:43 PM
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Re: Idle and acceleration issues.

VSS harness should be wrapped together with your Transmission wiring, pretty easy to access. The VSS is in your tailhousing correct?
VSS wires are spun together and shielded with foil to keep out "noise" for some reason the VSS wires like to pick up interference and the PCM has a hard time deciphering the noise so its critical they are in good shape the whole run

When I have had issues with VSS in the past you can spot it on the scanner while driving, instead of a nice steady scale the VSS signal will jump like 3mph to 11 to 23 etc instead of going 3, 4,5,6,7, 8, 9 , 10 etc

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post #8 of 80 (permalink) Old 05-05-2017, 02:53 PM
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Re: Idle and acceleration issues.

VSS is in the diff.
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post #9 of 80 (permalink) Old 05-06-2017, 02:20 AM Thread Starter
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Re: Idle and acceleration issues.

Yeah, i think the 4x4 models had it in the tailshaft housing right? Mine is definitely in the rear diff.

The speedo is reading smooth and steady. I would think a scantool would show the exact same thing the speedo is showing right?


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post #10 of 80 (permalink) Old 05-06-2017, 03:20 AM
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Re: Idle and acceleration issues.

Quote:
Originally Posted by Lt.Dan View Post
Yeah, i think the 4x4 models had it in the tailshaft housing right?
Absolutely not.

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