Surge during idle

engineersDURAMAX · 03-30-2006, 06:35 AM

I have noticed that while idling that there is a small surge(idle up). Is this normal? This is my first diesel truck so I am full of questions. So far the help has been great here. Thanks!!

Ray,IN · 04-01-2006, 09:19 PM

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.

engineersDURAMAX · 04-03-2006, 04:30 AM

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.

Ray,IN · 04-16-2006, 06:16 PM

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.

engineersDURAMAX · 04-17-2006, 05:32 AM

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.

C.A.P · 08-22-2006, 06:39 AM

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

Mavdog32 · 09-08-2006, 04:41 AM

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

tmougeotte · 10-17-2006, 09:15 AM

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.

Mavdog32 · 10-17-2006, 09:37 AM

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.

tmougeotte · 10-19-2006, 07:25 AM

I changed all my fluids and filters now it is surging and the engine light came on, thinking its the FPR time to see a dealer I guess.