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RPM's shuld be smooth and constant at idle if all is well. The most common culprit is a tiny air leak in the fuel system somewhere. Inspect the flexable fuel lines from the tank to the fuel pump, if there is even the tinest air leak, surging, hard starting, and infrequently small drops of fuel on the driveway happen. Flexable fuel lines fail from the inside out, so if in doubt, replacing the line may be prudent depending on the age of your truck.
 

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Discussion Starter · #3 ·
Is this a common problem? This didn't happen until I ran some cleaner thru it. A friend of mine said it sounded like a fuel pump to him!! Would a fuel pump cause this also? BTW thanks for the help, I am very new to the world of diesel.
 

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Does the "service engine soon" light come on? If not, the problem is something GM didn't consider. The fuel (injector) pump shouldn't be causing this unless you have purchased contaminated fuel and your fuel filter failed. This is the reason for injector failures on certain years of trucks. Diesel fuel has a natural affinity for water, and condensation in the empty part of your fuel tank will accumulate a surprising amount of water in your tank, especially when the outside temperature swings large amounts from days to nights. The flexible fuel lines deteriorate from the inside out, so when it's noticeable, the inside is really bad. The lining may swell and block fuel passage, suck in air without leaking fuel out, or simply reduce the amount of fuel flowing. If your truck is over 3 years old it's worth an inspection because of your complaint. I'm only an amateur so don't take my advice as gospel.
 

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Discussion Starter · #5 ·
NOPE there is no SES light! But, I think I found the problem. When I bought the truck I used som LUCAS injector cleaner. I beleive this is my trouble. It was strong enough to break loose the crap but not to disolve it. I ran some DIESEL KLEEN in it and all my problems went away, so I am good now....at least for the time being.:thumbsup
 

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loopy idle can also be a bad fuel pressure regulator they have been known to cause this type of idling
 

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Hey Engineer whenever you get the problem fixed let me know!! I am having the same problems. If I am not stepping on the brake enough I actually jump forward when it does it. Craziness huh
 

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me too

I am new to the diesel world as well and having the same idel surge when the engine is cold. how should I approach? I've heard the FPR could be bad but is covered by warrabty but I have also heard running a additive to clane the sysytem will do the trick? Any suggestions would be great.
 

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i think the additive is a reasonable first step and is the most cost affective. I would think that you would want to change out your filter after running it through a tank of diesel.
 

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Maybe, possibly could it be the injectors. I know that in my truck they extended the warranty on the injectors due to a problem with them. Not sure of the specifics but maybe you could look into that. Then again I cant imagine an injector would cause engine surge??
 

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got it back....

well picked it up today and turns out the block heater caused several codes making the sesors get out of wack and thus i was having idel surging and smoking. Who would have thought. anyone else have this issue?
 

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my truck has had a lopey idle since it was new kind of like a race motor with a big cam nothing ever found to be wrong with it although i have been told that some vehicles will change idle speed with the o2 content of the air but this is too regular to be that i think
 

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I'm new to this forum, but for months I've had this "parking lot surge" problem. My normal service at the local GMC dealer said to fix the problem just buy a new truck. No help in other words ....! I might add I have 273,000 more or less trouble free miles on our 04 LLY Duramax, anyway, I took it to the local Chevrolet dealer and the problem was found quickly. It was the fuel pressure regulator. When checked it was producing reading all over the board at idle. So maybe you, like me, need to try another dealer. Good luck, Rofran
 

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Has anyone had a kind of chattering noice and lost power with the idle surge as well? My truck has done that a few times but I figured it was just some water in the fuel.
 

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A lot of times, the Fuel Pressure Regulator is to blame for surging at idle. It can also be to blame for your chattering and loss of power because its not "regulating" the fuel flow like it should.
 

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Surge follow up

It has been 3 months & 12,000 miles since my surge problem was fixed. I'm happy to report that it has not returned so the fuel pressure must have been the problem. My 04 GMC truck is nearing 292,000 miles and is running like it was when new.
 

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When I had my injectors replace in Janurary of this year, I has an everso slight surge and the mechanic said to run some standyne fuel additive thru it. They gave me my first bottle of it and that really helped. He said that the fuel pressure regulator was weak and keep using standyne. I can't find it locally so I hve been using Diesel Kleen and seems to work. I hope I can find standyne soon cause it worked a little better than the Diesel kleen.

Hope your surge goes away!

duramax-rob
 
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