Rough idle after hard acceleration????????

jktcummins

jktcummins

24v GOD!!!! HAHAHA
Joined
Apr 1, 2007
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Ok so i finally got the HRVP and really like it. However i am still see the rough idle and sometimes engine dying after a real hard run. One time before the pump it was almost like the pump cavitated. Truck would not start it had to have had air in the lines.

After i put the HRVP on i was hopping that the hard starts and the rough idle would stop.

What can it be. I have the fass and it never sees less than 10psi. I have tried two sets of injectors, replaces the IAT and MAP.

It only does this after a hard acceleration. Sounds like there is air in a fuel line. You can tap the pedal just a little and it will stop.

Does anyone have a clue what might be causing this.
 
i have the same problem with my truck running a SOVP w/.093 line. i took off the lines and fixed the problem. So...........i really don't know in your case. I thought i was the only one with that problem haha
 
Some trucks seem to have an issue with that. It's various things that cause it but mainly it's caused by the pump cavitating when you back off to fast after a full throttle run.
 
Well on the street you can back out of the trottle and come to a stop and it sounds like a big block with one monster cam. Hit the throttle a little and its gone. I keep want to say it has to be the HRVP but it did it before the pump.
 
You didn’t mention the .093 tubes before when we were talking earlier.......

This is my guess with the VP-44 and larger lines/tubes:

You have an injection pump that is designed for a certain size line. It can keep pressure up in that line because its volume output can keep pressure up to pop off the injectors. If you increase the line size and/or tube size, you just increased the volume the VP-44 has to fill to make pressure. Under full to part throttle, this might be ok. BUT when you jump off the throttle, you just dropped pressure in the line and the pump is going back to idle fueling and its not enough to pressurize (fill) the lines to pop the injectors with the correct timing...so idle seems choppy. Plus the ECM is freaking out, wondering why its doing what its doing and starts to do its fuel dance (By cutting back and then adding in rapid succession to maintain idle) that many see with big injectors when lugging the engine. Once you get pressure back up and it stabilizes, your idle can take over and it will run ok. I bet you go back to stock lines or tubes, you will see this issue go by the way side.
 
I have pulled the tubes and those injectors out and gone with my old jammer 4's
 
I called and II and they said it is just fuel puddling up in the bowl. And when you give it a little throttle it clears it up.
 
I have a draw straw in the tank. Your truck would rough idle after a hard run just like there was air in a injector line?????
 
Whats it take to fix the dang thing. I talked to haisley's today and van said to try and stretch the return spring just enought o get closer to 20psi. He said that back in the day before FASS they were experincing the same thing. But once they started using FASS it cleared up.

He said that i am actually draining the fuel in the injector lines just enought to drop the pressure in the lines. He said if you can increase the psi going to the inj pump just a little that you might be able to stop it.

Does that sound like a winner????
 
Yes you would need more psi going to the inj pump....... lines are running dry.
(That's what it sounds like to me- and if lines are running dry that injection pump may be getting hurt too......)
 
How do you increase the pressure going to the inj pump? What else can you do to keep from draining the lines to the injectors.
 
i've been running 20 psi outta my fass and it still done it, and i even have a 1/2 I.D. pickup tube. Strange??? unless it fell off???hahahaha
 
Same here i have the draw straw in the take and it still does it. I am going to replace all my fuel lines redue all my fittings. Dan at fass said he had heard of the fuel line actually failing inside the line and causing a blockage.

There has has to be something to fix this.

I dont see how i can be draining the inj lines. It was doing the same thing with just a edge drag comp and jammer 4's. Its done it for a really long time. Just a little worried about my new ing pump.
 
Anyone have any other ideas as to why its doing this. I really dont thing its draining the inj pump because it was doing this with just a drag comp and jammer 4's.
 
Lots of ideas why it's doing it, but no solutions. Fact of the matter is, if you left off quick enough after a hard pass you will air lock a VP44. The combinations that seem to make it worse is high boost, and large injectors. You can tell how much hp a VP44 truck is making, by looking in the drivers side door pocket for a 19mm wrench. :hehe:

Paul
 
What's strange is not all of them do it. I know mine I can have the TST on 9 and be balls to the wall and suddenly let off and I don't have the problem. Another buddy of mine with mach 6's and a 6spd HO doesn't have the problem either.
 
its the Edge comp that makes it more prone i think...

my truck did it with stock turbo, 100sticks and Edge Comp, and when i switch to a bigger turbo, and bigger sticks. due to my young/heavy foot and driving style, it happened to me on average once a week.

went to bigger turbo and bigger sticks yet again, pushing 55psi now on 62lp(minute or hour) sticks with a TST/smarty...no more locking the pump up when letting off quick, it might idle rough for 10-15 seconds but does not stall.

have a buddy with stock turbo, 100hp sticks, comp box, when he lets off after a sled pull...truck stalls and vapor locks the lines

its not fixable, just try not to let off too quick without popping it in neutral and maybe pumping the go pedal once or twice to keep the truck running.
 
I can understand it doing it with a smarty, edge, some 180 sticks, .093 tubes, and a hrvp. But i dont understand why it would do it with just some 120 ph sticks, and a drag comp.

Or with 120 sticks, and smarty. That just doesnt seem like it would drain a pump expecially a HRVP.

I feel like i have another problem somewhere.
 
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