IVS and driveability issues
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Junior User
Joined: Feb 2012
Posts: 72
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IVS and driveability issues
This may be old news to the veterans on here, but I figured something out today that I thought I'd share to maybe help somebody else. My truck with a ZF-5 has always been a little difficult to drive slowly, like in parking lots and such. I could idle around in gear just fine, but if I pushed the pedal it would accelerate too much. Even in neutral, I couldn't get RPM to hold anywhere below about 1500- it was idle or 1500+. Sitting at my desk at work and reading FTE 
I started thinking about the IVS, so I went outside and took a look at how it actually worked. It turns out that the PCM doesn't act on any TPS input until the IVS opens (closes?) to tell it that the pedal has been pushed. My IVS wasn't actuating until the pedal had moved an inch or so, and by then the TPS had moved quite a bit. I shaved a little off the plastic IVS plunger and bent the tab on the pedal so that the IVS gets actuated within the first 1/8" of pedal travel, and...Magic! I have fine engine speed control, just like it's supposed to be. I can creep around in 1st gear now without revving and bucking like an idiot, haha.
I started thinking about the IVS, so I went outside and took a look at how it actually worked. It turns out that the PCM doesn't act on any TPS input until the IVS opens (closes?) to tell it that the pedal has been pushed. My IVS wasn't actuating until the pedal had moved an inch or so, and by then the TPS had moved quite a bit. I shaved a little off the plastic IVS plunger and bent the tab on the pedal so that the IVS gets actuated within the first 1/8" of pedal travel, and...Magic! I have fine engine speed control, just like it's supposed to be. I can creep around in 1st gear now without revving and bucking like an idiot, haha.
Postmaster
Joined: Sep 2007
Posts: 4,195
Likes: 6
From: Medford Oregon
This may be old news to the veterans on here, but I figured something out today that I thought I'd share to maybe help somebody else. My truck with a ZF-5 has always been a little difficult to drive slowly, like in parking lots and such. I could idle around in gear just fine, but if I pushed the pedal it would accelerate too much. Even in neutral, I couldn't get RPM to hold anywhere below about 1500- it was idle or 1500+. Sitting at my desk at work and reading FTE I started thinking about the IVS, so I went outside and took a look at how it actually worked. It turns out that the PCM doesn't act on any TPS input until the IVS opens (closes?) to tell it that the pedal has been pushed. My IVS wasn't actuating until the pedal had moved an inch or so, and by then the TPS had moved quite a bit. I shaved a little off the plastic IVS plunger and bent the tab on the pedal so that the IVS gets actuated within the first 1/8" of pedal travel, and...Magic! I have fine engine speed control, just like it's supposed to be. I can creep around in 1st gear now without revving and bucking like an idiot, haha.
I started thinking about the IVS, so I went outside and took a look at how it actually worked. It turns out that the PCM doesn't act on any TPS input until the IVS opens (closes?) to tell it that the pedal has been pushed. My IVS wasn't actuating until the pedal had moved an inch or so, and by then the TPS had moved quite a bit. I shaved a little off the plastic IVS plunger and bent the tab on the pedal so that the IVS gets actuated within the first 1/8" of pedal travel, and...Magic! I have fine engine speed control, just like it's supposed to be. I can creep around in 1st gear now without revving and bucking like an idiot, haha.Reps sent ...
Posting Guru
Joined: Aug 2004
Posts: 2,417
Likes: 4
From: Braham MN
Its one of the best mods that can be done to these trucks in terms of driveability. Every Powerstroke I or any of my friends have owned I did this mod to. I lay on the floor and push the pedal till I hear it click, keep bending the tab until I barely push the pedal and it clicks. I think it was called the hot foot mod.
Diesel Rod
Diesel Rod
Posting Guru
Joined: Aug 2004
Posts: 2,417
Likes: 4
From: Braham MN
I can hold all my trucks at 700 RPM, its well worth it. I suggest a long handled pliers to bed the tab, no need to file down the switch plunger.
Diesel Rod
Diesel Rod
Trending Topics
Fleet Owner
Joined: Aug 2004
Posts: 20,419
Likes: 197
From: AZ
I did this mod a long time ago but think mine needs a little more 'bending'. Also with the 140 IDM mod made it a little touchy.
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Cargo Master
Joined: Jul 2010
Posts: 3,014
Likes: 115
Ah... So much better. I didn't do it as much as I could have. As I get into the throttle, it will pop up to 1,000 RPMs or so. But as I take my foot out of it, I can get it down to 700 RPMs or so. The difference between that and 1,800 rpms is huge, though. I can have it idling in gear and give it throttle without it giving me whiplash now. It's much more comfortable.
Post Fiend
Joined: Dec 2009
Posts: 15,505
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From: Livoina,La
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