Engine Stumble?

turboman1

turboman1

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Aug 20, 2008
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248
posting this for my cousin,

He just got done installing brand new reman VP44, 90hp injectors, and 165 Air dog set at 15 psi.

The problem is when he is coming to a stop light and pushes in the clutch to slow down the motor drops below the normal idle rpm and stumbles until it finally comes back to normal idle. It does the same thing if you free rev it to 2000 rpm and just let off the throttle.

What causes this? Bad electronics, too much/little fuel pressure?

The truck doesn't have a box tuner on it

Thanks for the help

Adam
 
possibly a cam/crank sensor going out, loose injector line(s) causing to suck air, or the cross tubes arent sealed to the injectors right. Hard starting?
 
Truck is not hard to start at all. All the cross tubes went in right. Truck ran fine before all the new stuff went on.

I was searching and read that it could be the ecm shutting off the fuel pump for a second when you let off the throttle. Any truth to this?

Thanks
Adam
 
Under hard pulls it can be yes. I dont see how it would be doing that while cruising. It will sense that you've let off the throttle and cut the fuel off instantly. Its called "Pump Dump" if im not mistaken.
 
Well that is not what it is doing...it is just under cruising conditions and you push the clutch in and the motor rpm drops too far and it start stumbling until it can get back to normal idle.

Is there a scan tool he can buy or borrow that will tell him what the pump is doing or if anything else is wrong.

By the way there are no codes being thrown.

90 hp sticks could not cause this kind of problem I wouldn't think. Thus I would think it is something happening with the fuel pressure or something electronic with the new Reman injection pump.

In the mean time is it safe for him to drive if the fuel pressure is there all the time?

Thanks

Adam
 
Mine does the same thing ever since I swapped injectors. I'm guessing the pop pressures are off a little. It's annoying but I usually just give the throttle a quick tap after I push in the clutch and it runs normal. I've been driving it for a year like this and nothing bad has happened.
 
2001ctd2500 said:
Mine does the same thing ever since I swapped injectors. I'm guessing the pop pressures are off a little. It's annoying but I usually just give the throttle a quick tap after I push in the clutch and it runs normal. I've been driving it for a year like this and nothing bad has happened.
Click to expand...

Is that the only thing you changed at the time?

Adam
 
2001ctd2500 said:
Yep, I can put my old 150s in and it goes away. Whose injectors are they?
Click to expand...

Diesel Auto Power built the injectors. He wanted 70 hp ones but all they had were 90hp so he went to those. I image the injector is not the physical problem, but how it makes the pump respond is what causes this?

Thanks
Adam
 
mine does the same thing. the odd thing is that it only does it when it is about 75 degrees or hotter outside. I can roll up to a stoplight with the clutch in or have it in neutral and it will drop rpms way too low and kind of bounce around until i get below 5 mph. Once it is under 5 mph it straightens up and idles perfect. It only happens when it is hot out and rolling to a stop while in neutral. it will even die sometimes when coming to a stop while in neutral. i was thinking it was something wrong with electronics because of the heat and how it will straighten up when under 5mph.
 
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