Occasional Rough Idle in 03

[mikennola0515]

Any help on the following would be appreciated.

I have a 2003 2500HD with the D/A combination and am at about 66K. Bought the truck new in Sept. 03.

Lately I've noticed a slight engine shudder when coming to a stop. I've seen no loss of power, fuel economy (I manually check the mileage at every fill-up) or smoke, and the truck starts fine. I have religiously performed all scheduled maintenance, including fuel filters, and baby it (only towed with it a handful of times, max load 8k lbs.). I did run it out of fuel once about eight months ago, but the problem is more recent than that. I have never used any additives for fear of warranty issues, and the truck is completely stock.

I am concerned that this may be an injector issue, and want to get in front of it expecting potential difficulty in dealing with GM.

I'm due for a fuel filter replacement within the next month, and thought that I would investigate the matter at that time.

I'm a bean counter by trade, so you'll have to dumb down the technical speak for me:).

Thanks in advance,

Mike

[Duramaster]

What probably happened is that the Turbo Encabulator has come out of time with the piston return spring causing the injector piston oscillations to waiver on the rich AND lean side therefore resulting in what you call rough Idle but to those of us in the trade call it ther sound of economy.................. Don't buy that? I don't blame you :D I'm just KIDDING! Here watch this and laugh some more http://www.youtube.com/watch?v=rLDgQg6bq7o&feature=related

Seriuosly though, next time you take your truck in for the fuel filter, have the dealer observe the balance rates of the injectors. It should be 0 +/- 6.5 mm3 in gear and 0 +/- 4.5 mm3 in P/N. The injector policy does not cover smoke or balance rate issues, BUT a good tech can MANIPULATE the scanner/ truck to show the injectors as failing and therefore score a new set for the customer! ;)

Enjoy the training video!! :D

[DmaxMaverick]

We can't assume a fuel filter is OK until we reach X amount of miles. The service interval is only a recommendation for the times everything goes as planned. If you are changing at 15K, it's entirely possible this filter didn't make the distance. 15K miles, according to many reports here, is the upper limit for normal use, and is too long if there are any fuel issues along the way. As a general rule, as with all Diesel engines, any time there is an issue with running, change the filter FIRST, before proceeding with any suspicions or diagnostics. So.....

1. Change the fuel filter.

2. Drive it.

3. Try to repeat the complaint. If it goes away, it was the filter. If it doesn't go away, it was the filter, and you have other issues. Cross that bridge when you get to it. We'll be here when you do.

[madmatt]

Yep I say every 10k on the fuel filters.

[mikennola0515]

I'll take the advice here and wait to bring the matter up until after the fuel filter change.

Mike

[NeilLB7]

I have exactly what you describe as well. I've narrowed it down to the fuel pressure regulator. Usually it will idle "rough" or different for about 20 seconds after its all warmed up and I come to a stop. But it will clear up and totally smooth out. I can feel it in the steering wheel and the floorboard. When it smooths out its obvious. Once in a great while it will be idling smooth and then act like it wants to rev for a split second. Then go into rough idle...then right back to smooth.

Runs starts perfect, good mpgs, no smoke, very powerful otherwise and smooth.

142.000 on original injectors.

[mikennola0515]

Neil,

Did you replace it?

Mike

[NeilLB7]

Not yet. The issue comes and goes. I think I'll wait until its -10 F outside to tackle this. :D

Actually I'm in the process of installing a natural gas ceiling mount furnace in my garage so I can do things in the winter months. I figured I will need injectors sooner rather than later at 150K on the originals. So I'm planning to do several things at once to minimize time spent under the hood. Kinda a "all in one" refresh of the things that go bad.

[Mark Rinker]

All they said, plus:

Don't be afraid of fuel additives. Could be the answer to your problem, if you have two injectors hanging up.

I like Howes. Truck stops carry it. Buy a big jug and run it for the next 5 tankfuls or so, see what happens.

Can't hurt - and won't void your warranty.