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My Truck Surges At Idle

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fawazbarraj

Seasoned Expediter
HI,
I Have a 2001 Peterbilt 330 Straight Truck......Suddenly It Starts To Surge At Idle..(Unstable Idling) When I First Start The Truck It Will Idle Normal For about 10/min after That It starts To Surge......(Unstable Idling) This Is Only at Idle... and It Does Not Happen While Driving... Truck Drives Excellent and No Problem With Fuel Pressure.....I Had It Checked and Tested By Both Peterbilt and Cummins Dealer Many Times and They Could Not Find Out The Problem.....I Have Been Driving This Truck With This Problem For about a Year Now ......But I am Trying To Fix This Issue...
Please If Any One Have an Idea What This Could Be.....Please Write me Back.....This Is Could Be an Electrical Problem...I Have Changed Some Electrical Parts But No Luck...

Thanks For Reading
 
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Rocketman

Veteran Expediter
My truck ('01 FL) with the 12.7 Litre Detroit does the same thing. What I've always done is to kick the idle up from 800 to about 1050. That seems to smooth it out and after a while, I can usually let it drop back to 800 and it will run smooth.

I was at a FL dealer last week and asked one of the techs about it and he told that many times you could have the software on the ECM updated with the latest version and that would stop it. Kind of like updating the operating system on your pc.
 
jaminjim

jaminjim

Veteran Expediter
What they finally did to mine was to knock the idle down from 730 rpm's to about 630 or so. They said that it was hunting for the idle speed. By that they meant that the ecm would sense to low of an idle and then when it saw to high of an rpm it would send less fuel, so it was hunting for the correct idle. once they backed the rpm down at idle it went away. My truck was worse when it was cold outside.
 
arkjarhead

arkjarhead

Veteran Expediter
I had a truck do that. All that I could figure out was every once in a while it would get a double shot of fuel while idling. I know this sounds crazy. It would never do it if I was idling after running. Only when idling from cranking up while letting the diffrent pressures build and motor warm. I don't like running a cool motor, but that's just me. It seemed to be worse in cooler temps like jaminjim stated. My dad said something about they can get a shot of warmer fuel and it can cause the surge. By the way the truck I'm talking about was a 2000 FL Century with a 430 Series 60 Detroit.
 
davekc

davekc

Senior Moderator
Staff member
Fleet Owner
If a dealer looked at it, then one would be under the assumption they did a voltage test at the fuel pump.
If that is ok.....what is it showing on the ECM activity report?
That should catch any irregularities at the injectors.
Flashing the ECM wouldn't hurt, but may still not correct the problem if it is a speed/rpm sensor that is having a issue.
I would have to think that between all of these, it should tell you something.
Maybe even a slight leak with the after cooler will cause your symptoms.
Not sure on a cummins, but I have also heard that a temp sensor at the intake will cause this as well. It is sending the wrong temp to the ECM and giving it a false reading.
 
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ratwell71

Veteran Expediter
Where did you last fuel up? Alot of flooding going on, it could be as simple as water in your fuel tanks.
 
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fawazbarraj

Seasoned Expediter
No Its Not a Water In The System Because We Have Cleaned The System From Water.....and This Problem Has been Going On For Over Seven Months Know............Thanks anyways.
 
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fawazbarraj

Seasoned Expediter
I Was Wondering ...What Do You Mean By Flashing The ECM ....Is This Some Thing Can Be Done By The Dealer Or any Mechanic...??
 
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fawazbarraj

Seasoned Expediter
Sorry ....But Flashing The ECM Is Like Reseting The System.......Is That Correct??
and I Hope That Will Fix It Becase Its Very Noisy...
 
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ratwell71

Veteran Expediter
I had some issues with my last truck with it surging, but it only happened while driving and it ended up being the fuel sensor. I drove it that way for a while and it left me stalled at a red light. Had it replaced and no more surging.

Hope you get it figured out. These guys out here can give you some good advice.
 
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ratwell71

Veteran Expediter
fawazbarraj said:
Sorry ....But Flashing The ECM Is Like Reseting The System.......Is That Correct??
and I Hope That Will Fix It Becase Its Very Noisy...
Click to expand...

This flatlines the ECM so that they can reload the software. I hope that is all it is. Very cheap fix.

Did your truck register any fault codes?
 
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fawazbarraj

Seasoned Expediter
Thank You Very Much For The Info... The Reason I am asking Here Becase I Know Some Guys Here They Have Had This Issue With There Trucks.........You Wont Belive How Much Mony I Have Spend Trying To Fix This Surging....But No Luck and Every Dealer Say Some Thing Different.......Last One He Wants Me To Put a New Fuel Pump....Then I decided To Go Online and Ask.......
 
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ratwell71

Veteran Expediter
When my fuel sensor went out it did not log any codes. It ran crappy for several months. Then it died a couple of times when I would stop. Almost like it lost its prime. So I had a mobile unit come out with a new fuel filter thinking that this was the problem. I had water in my tanks from a fuel stop prior and thought it possibly messed up my fuel filter. Had experience with this before and thought it was surely the problem. Nope. So then I had it towed. $500 plus dollars later they told me they had to replace all my batteries and the fuel sensor.
 
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ratwell71

Veteran Expediter
The fuel sensor for my truck if I remember correctly was around $150. And it just screws in like a spark plug.

I would go with what Dave said and have a voltage test done on your fuel pump.
 
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ratwell71

Veteran Expediter
Does it only do the surging when you have cruise control on?

Does it do it right after starting your truck without the cruise on?

If so, how long after you are idling does it surge?
 
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