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Diesel Mechanic
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Discussion Starter #1
Hi everyone. I'm a diesel mechanic working out of Tampa Bay Florida. I recently did an engine swap on a 2007 International Vac truck. It's a 7400 Maxxforce DT. Everything has gone well, except for one little problem that I cannot for the life of me figure out. I don't have any throttle response. Cruise control works and the engine idle up on the front reel works; both of which will increase and decrease my RPM's, but the pedal does nothing. I've had it hooked up to the computer, no codes, and I can see on the computer that the ECM is reading the pedal. Anyone got any ideas?
 

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Diesel Mechanic
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13 Posts
Discussion Starter #2
I've also found that if I activate the cruise control, rev up the RPM's just 1 notch and then shut off cruise control that the accelerator pedal begins to work. However, as soon as you shut the truck off and restart it the pedal no longer works until the cruise control is activated again....
 

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Junior Member
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323 Posts
You state that it is reading the pedal.
Are you just looking at full sweep or can you show percentages from 0-20% ?
 

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Diesel Mechanic
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13 Posts
Discussion Starter #4
Hi Jasong, thank you for your reply. On ServiceMaxx and Prolink it shows full sweep in percentage; meaning I can watch it go from 0-100%. However, when testing at the TPS on my pedal position wire (A) the voltage is only going from 0.68-3.8v, rather than the full 5v. And I have a full 5v at my vref wire (c). I'm leaning towards the TPS, but I really pulling the trigger on it as I've already replaced so many components, i.e, turbo, egr coolers, egr valve, boost sensor and exhaust back pressure sensor. In addition, when I run the KOER test it continuously fails for not building sufficient back pressure, and I've talked to both International, and Jasper where I got the motor from and Jasper seems to believe that the TPS would cause this condition. Anyway, any help you may be able to provide would certainly be a ray of sunshine in my now dark world. lol
 

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Diesel Mechanic
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13 Posts
Discussion Starter #5
So now I've replaced the Accelerator Position Sensor (Foot pedal) and STILL no response other than bogging down slightly. I don't know what else to do
 

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Junior Member
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323 Posts
0.68-3.8v is within normal range.
You'll never see 5V on a working sensor.

I'm over my head here,
Is there a sensor that tells the ECU if the engine is in neutral? I've seen this on cars to prevent over revving out of gear.
 

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93 Posts
ivy
I feel your pain. There is a provision for a PTO interlock to disable the throttle pedal there is
likely a provision for a bus door throttle lock out as well and possibly a remote throttle that could
disable the throttle pedal.

Did you use the ECM off the original engine?
Some throttle pedal sensors have 2 potentiometers and some use an idle validation switch.
At least that is what Cummins called it.

Terry
 

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Diesel Mechanic
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13 Posts
Discussion Starter #8
Hey Terry, Thanks for your response. This truck does have a remote idle switch, which works and there isn't a PTO on this truck. This is a huge Vac truck which has a hydraulic pump that runs off the front of the engine, and a pony motor on the rear of the truck. I did use the original ECM and have changed the throttle pedal to no avail. I've had two other mechanics, much more seasoned than I am, look at it. They both spent several days attempting to diagnose this issue, again, to no avail. I'm just truly at my wits end with this thing. I don't understand how the cruise and remote idle can work seamlessly and yet the throttle pedal doesn't. I further can't understand why the truck keeps failing the KOER test due to low exhaust back pressure as I've checked everything there is to check concerning this issue. I mean, I've even pulled the valve cover off again to make sure that all the valves were good. When I'm running the truck, I've monitored the desired exhaust back pressure and have compared it to the actual back pressure and they always match. I just don't get it.
 

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Junior Member
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93 Posts
ivy
Is there a way you can get the ECM re-flashed. It may have out of date software or may have developed a glitch.
Is there a chance that one of the pins in an ECM connector could have bent over
and not gone into its mating terminal in the plug when the plug was installed in the ECM.
 

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Diesel Mechanic
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13 Posts
Discussion Starter #10
Hey Terry G, Had the ECM and BCM flashed the other day and put them back in yesterday evening with no changes. I have noticed that the Engine Load % is way above normal. At idle the engine load is running at about 75-80%, which it should be down around 20-40% at idle. I disconnected the front hydraulic pump which runs off the crank and the engine load dropped about 20% and gave me a little more pedal. Now instead of reacting at around 33% pedal it's responding at around 25% pedal, and the pedal works without having to turn the cruise control on and off. But even with the drop in engine load it's still running high at around 60%. The only other load on the truck is the transmission....and prior to the engine swap there weren't any issues with the transmission that I was aware of and yes I was able to mate the engine and the transmission without any problems and the truck does move at idle, both in forward and reverse and there's no binding from the torque converter.........
 

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Junior Member
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93 Posts
Ivy
Is there a dealer that would be willing to submit a case file through IKnow for you.
Navistar's engineers would review it and probably would have a solution.

Terry
 
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