2004 Sierra 5.3L: Rough Idle

[GMCSierra04]

Hi, I have a 2004 GMC Sierra with the 5.3L V-8 with 10,500 miles. A few weeks ago the idle quality began to get a little rough and now it has a very noticeable stumble. This is only present when idleing and there are no other driveability symptoms. I did some basic checks and the plugs are gapped correctly and are in good condition, all the plug wires are under 1K Ohms and I pulled and inspected all the connectors to the coils and fuel injectors. My question is what is the most likely cause of this? I will take it to the dealership seeing that its under warranty but I just wanted to get some ideas of what could be causing this. If there is anyone out there who has had a similar experiance like this or any GM technitions that have had similar complaints on the RO's, feel free to let me know. Thanks everyone!

 

Zack

[GMCSierra04]

Anyone??? Come on now, please.

[Butch 02 Denali]

I'm guessing the secrets in your list of mods....K&N filter. Nothing wrong with the K&N, but if overoiled, the excess oil gets on the wires in the MAFS and makes it run rough.

Get yourself some electronic parts cleaner that is residue free and plastics safe.

Remove the MAFS, spray down the little wires inside with the cleaner, I usually spray from both sides, DON"T TOUCH THEM. Let it dry and reinstall. Problem solved. Next oiling of the K&N, lay it on paper towels for 10 minuets after spraying to suck off the excess oil.

[GM-Tech]

It's a little young, but cleaning the throttle body is easy and something you can do yourself in minutes, so I'd give that a try first. We have a bit of a problem with that.

 

Otherwise, there are just too many things that could cause this to even take a guess.

[gilliam]

It's a little young, but cleaning the throttle body is easy and something you can do yourself in minutes, so I'd give that a try first.  We have a bit of a problem with that.

 

Otherwise, there are just too many things that could cause this to even take a guess.

 

<{POST_SNAPBACK}>

 

 

 

My '03 does the same thing. Especially while in gear with my foot on the brake, like at a stoplight. Almost feels like a slight miss. The dealer claimed that this was a fuel 'shudder' causing the rough idle. I've heard several others complain of the same problem, so you would think GM could figure it out.....

[GMCSierra04]

Thanks for all the help guys! I have had the K&N in for about a year and have only cleaned it and re-oiled it 1 time. I let the thing sit for about 20 mins, patted and wiped the excess away to minimize the possibilities of any problems. I inspected the MAF wires and there doesnt appear to be any oil or debris on the hot wires so I'm not sure. I should just take it to the dealership and see what they say about it. I also got this rattling noise which sounds like its coming from right behind the instrument cluster or bottom of the A-pilar. I hope they can find the problem.

[325]

It's the throttle body. I have had this problem on two separate Chevy trucks and the problem was solved when the throttle body was replaced. Those things are finicky and the K&N filter only aggravates the problem. Just my opinion, but deep six the filter and consider yourself lucky if the replacement is covered under warranty.

[GM-Tech]

  The dealer claimed that this was a fuel 'shudder' causing the rough idle.

 

A fuel shudder? I never heard of such a thing. What the heck is that supposed to mean?

[100R1]

codes ??????

 

have you put it on a scanner ?????

 

 

you may have triggered codes even though your service engine light does not come on.

 

you can start throwing parts at it to fix or do what most professionals do. Scan It.

 

 

if you do not have a scanner or a friend that owns one, you may be able to get the use of a FREE scan from your local auto parts store. Pep Boys and a local NAPA store in my area has FREE loaner program for them. Make a phone call to your local part store to find out more.

 

Not to late to add a scanner to your Santa Wish List !

[GMCSierra04]

I had my truck in school not too long ago and hooked up the Tech II and there were no DTC's present or in history either. Everything else looked fine too, the fuel trims, fuel psi, injector PW's and so on. One thing I forgot to mention was the when I had it hooked up to the Snap-On Modus, the firing Kv for cyl#7 was only 6Kv while every other cylinder was around 14 and 15Kv, where it should be. The spark duration was around 1.5 ms for pretty much all cyl's too, but I had to re-test because I dont remember. I will pull the filter out and take it to the dealer soon and if it was anything related to being crapped up I will ditch the filter and just use the AC Delco, probabaly what I should have done in the first place with a MAF eqipped vehicle. Thanks everyone.

[budhayes3]

I'd try cleaning the throttle body just for poops and giggles. Like GM-Tech said, 10.5k seems a little early, but with the K&N you might have some extra gunk working it's way in there.

[GMCSierra04]

Hi again, I cleaned up the throtle body this morning and there was just a little bit of junk behind the throtle plate but not much. Started it up and drove around and it still does it like before so to the dealership I go. Thanks for all the advice everyone.