[Martin #6]

Under heavy acceleration or pulling a load, the motor starts to develope a miss and shudder like it's defueling, but no light. I'm maxing out at 20 psi in the 60 tow and 80 econo settings. I really start to notice the motor missing when I get to about 2/3rds of pedal. Anything after that, the truck just falls on its face. I do have the regulated return set at 64 psi.
Pulling my 7k trailer up the hill on HWY 80 last night from Auburn, in the 60 tow program I would steadily loose boost pressure, the egt's would climb to 1250 degreres and I would loose speed. If I smashed the pedal to the floor, the motor would start to shudder and miss, the boost gauge would flutter and drop pressure and the egt's would drop to 1200*. Since I had nothing to loose, I changed over to the 80 econo program and the truck pulled much better. If I kept the speed at 55-60 mph, the boost would stay at 18-20 psi and the egt's would hover around 1100-1150 degrees and pull steady.
So this one really has me confused. I've tried everything to get this truck to run better with lower egt's. I've changed turbos, air intake systems, different chips and most recently live tuning with the F-5 chip, new intercooler and up-pipes and have checked for exhaust leaks and boost leaks. I've found no leaks at all.
Any ideas what to check now? I'll check my fuel pressure for defueling once I get a new hose made to run a pressure gauge into the cab and I still have the ITP pre-pump kit to install. Could it be bad injectors or the pedal assembly? I'm still running the stock AB's at 106,000 miles.

 

[gregrob]

You know... funny you post this. I was going to post about a similar issue.

I can floor it sometimes, like gettting on the interstate, and it shudders and defuels or "holds back", if I let up on the pedal it takes off.

It also does this when I roll into the throttle, it will shudder lightly and lunge a time or two like something is holding it back, then finally come up on boost and take off.

If I got WOT from a dead stop I never notice it.

Not to hijack, hopefully we can find a solution together. I'm thinking of swapping pedal assembly with a friend and see what happens.

 

[NWSUPRD]

When my truck falls off under WOT like you are describing it is because of a slight loss in fuel pressure. As with Gregrob if I back of slightly pressure comes back up and all is good again. For me it is because I am asking for more fuel than the stock lift pump can deliver. To remedy this we will be putting on an Airdog soon.

 

[Wackerjr]

Under heavy acceleration or pulling a load, the motor starts to develope a miss and shudder like it's defueling, but no light. I'm maxing out at 20 psi in the 60 tow and 80 econo settings. I really start to notice the motor missing when I get to about 2/3rds of pedal. Anything after that, the truck just falls on its face. I do have the regulated return set at 64 psi.
Pulling my 7k trailer up the hill on HWY 80 last night from Auburn, in the 60 tow program I would steadily loose boost pressure, the egt's would climb to 1250 degreres and I would loose speed. If I smashed the pedal to the floor, the motor would start to shudder and miss, the boost gauge would flutter and drop pressure and the egt's would drop to 1200*. Since I had nothing to loose, I changed over to the 80 econo program and the truck pulled much better. If I kept the speed at 55-60 mph, the boost would stay at 18-20 psi and the egt's would hover around 1100-1150 degrees and pull steady.
So this one really has me confused. I've tried everything to get this truck to run better with lower egt's. I've changed turbos, air intake systems, different chips and most recently live tuning with the F-5 chip, new intercooler and up-pipes and have checked for exhaust leaks and boost leaks. I've found no leaks at all.
Any ideas what to check now? I'll check my fuel pressure for defueling once I get a new hose made to run a pressure gauge into the cab and I still have the ITP pre-pump kit to install. Could it be bad injectors or the pedal assembly? I'm still running the stock AB's at 106,000 miles.

Was it still doing it with Jody? When he was live tuning? Did he see anything with the scan tools?

 

[gregrob]

When my truck falls off under WOT like you are describing it is because of a slight loss in fuel pressure. As with Gregrob if I back of slightly pressure comes back up and all is good again. For me it is because I am asking for more fuel than the stock lift pump can deliver. To remedy this we will be putting on an Airdog soon.

I guess that's my problem then. Didn't know fuel pressure could make so much difference. I'm dropping to 23lbs under WOT

 

[Martin #6]

Was it still doing it with Jody? When he was live tuning? Did he see anything with the scan tools?

I went to the altitude of Denver for the live tuning since I live at 6,000 ft. The miss/shudder was happening during the tuning, but I didn't comment on it at the time, nor did Jody. My bad. I should talk to Jody and have him look at the files to see if he sees anything that would cause this. All this started to happen once I got the new F-5 chip and the BO.

 

[THEDIESELMAN]

Do you have the upgraded cable on your F5 chip and did you have BO when you got live tuned.

 

[Martin #6]

I can floor it sometimes, like gettting on the interstate, and it shudders and defuels or "holds back", if I let up on the pedal it takes off.

It also does this when I roll into the throttle, it will shudder lightly and lunge a time or two like something is holding it back, then finally come up on boost and take off.

I get the same sensation.

 

[gregrob]

Check your fuel pressure if you get the chance. You can hook up a manual gauge and tape it up outside on the plastic cowl.

 

[TerminatorEngineering]

Matt, do you have AutoE? If not, and you want to take a short drive, come down to Modesto and we'll take a look at it. Actually, Bill(KicknY2K) might have AutoE too, and he's closer. I'm a little surprised Jody didn't see anything, but we'll take a look.

Mike, I think your on to something. Also, when you go back to John Wood, have him shim those pumps.:doh:

Gregrob, oh boy, sorry dude, you can't be helped!:doh:

 

[gregrob]

Matt, do you have AutoE? If not, and you want to take a short drive, come down to Modesto and we'll take a look at it. Actually, Bill(KicknY2K) might have AutoE too, and he's closer. I'm a little surprised Jody didn't see anything, but we'll take a look.

Mike, I think your on to something. Also, when you go back to John Wood, have him shim those pumps.:doh:

Gregrob, oh boy, sorry dude, you can't be helped!:doh:

HA! he has the same problem and we start firing off solutions. but with me, noooooooo, something is wrong with gregbob's pile, he's an idiot, he's gay, it has a demon, etc

 

[Martin #6]

Do you have the upgraded cable on your F5 chip and did you have BO when you got live tuned.

Yes.

 

[Martin #6]

Joey,

No AutoE for me and I've been trying to get down to Bills for quite some time. I've got a CAC for Bill and a BB turbo for him to look at. Our schedules just aren't working out.
I'll get the fuel pressure tested before heading down though.

 

[gregrob]

Let me know what you find please. That may be our problem!

I'm also looking into the pedal assembly. Gonna swap one with a friend when we get time.

 

[TerminatorEngineering]

Matt, sounds good. I'm busy with the harvest for the next couple weeks, but after that, I'm wide open if you need help.

Gregrob,...................., I don't know what to say............., hopeless?:doh:

 

[gregrob]

go pick your nuts

 

[THEDIESELMAN]

go pick your nuts

I bet he has workers to do that for him.

 

[Wackerjr]

I bet he has workers to do that for him.

He wishes...................

Joey="the workers"

ointlaugh:oke:

 

[Charles]

My truck did basically the same thing.....

I ended up pulling the engine to find the hole in the pickup tube that was aerating the piss out of my engine oil to the point of inhibiting the injection system from even working.

Next time you change your oil, let the truck sit for about an hour or so and then drain the oil and catch some in a styrofoam cup. See if soda-can type bubbles make their way to the surface and then dump it out and see if there are air bubbles all over the sides.

Otherwise, my truck also does this when the fuel pump dies and I don't notice the gauge sitting on ZERO.

But don't worry, if it's fuel pressure falling out on you, you're just ruining your injectors, lol.

 

[gregrob]

I hope it's fuel pressure. Not because it's ruining my injectors, but because I dont want to pull the engine.

Although it's part of the plan for this winter anyway