What Causes A Slightly Rough Idle?

[hpracing10]

What can cause a slightly rough idle on an '03 silverado with a 5.3L? Once it gets warm, it has a very slight vibration every so often that I can feel while sitting in the drivers seat. What different things can cause this or what should I look for? Here are a few things that have recently been replaced that relate to the fuel system:

 

New Spark plugs-exactly 20,000 miles ago

New spark plug wires- 1500 miles ago

New fuel pump-1500 miles ago

New fuel filter-500 miles ago

New fuel pump relay-100 miles ago

 

I also try to run sea foam through the gas tank every other tank. And I also keep the throttle body cleaned up about every oil change. One thing that i have not changed since owning the truck is the fuel pressure regulator. How often do these go bad, and could this cause the slight vibration I am experiencing?

 

Other than the things I have listed, what else could possibly cause this vibration? Could it be from a dirty fuel injector, or could it be something with the fuel rails? It really isn't anything I should be too worried about I don't think, but I am sure, like many of you, I get paranoid by every little bump, burp and vibration that my engine makes.

 

Also, truck is meticulously cared for and well maintained and the engine has never had any major problems. Hopefully someone can fill me in on what to look for. Even if you don't know exacly what it is, I know that there are many top-knotch mechanics on this forum so I am hoping someone can just give me a brief rundown of what I can look for. Thank you in advance

[hpracing10]

nobody has ever experienced a vibration at idle? C'mon guys, just because I am not asking advice about a mod doesn't mean you can't reply! Our trucks have to be able to run good before they can look good!

[Jennabear]

Try a different gas station or octane. Have you cleaned your MAF and throttle body?

[Whocares05050]

I have an 04 GMC Sierra 5.3 and have asked 5 differant shops about the same freakin vibration and noones able to tell me. I still have the vibration and in the last month i have changed the oil, the wires, the plugs, intake, MAF sensor, cleaned the throttle body out, new exhaust, new intake, and still feel it! you are not alone. lol.

[texasblueline]

My '02 Silverado 5.3L had the same thing, it would occasionally idle a little rough. It was just barely noticeable, I could feel a slight vibration through the seat and steering wheel and it would only happen occassionally for maybe 15-30 seconds, then it'd fade away. I'm probably the only one who ever noticed the rough idle, just because it was my truck and I was a stickler about details. It had it the entire time I owned it (from 30K-118K miles), and it never appeared to cause any problems as the engine always ran great (I did have a very slight case of the GM cold start piston slap, though, but nothing else).

[salden77]

do you still have a slight vibration with the a/c, and defroster off? when i have either a/c or defroster on in my truck it causes a slight vibration at times, same thing happens in my mothers 04 suburban.

[Silverado4x4]

Running sea foam through the tank every other fill up is a awful lot. I would stop putting that in there for awhile and see if that helps.

[Silverado4x4]

nobody has ever experienced a vibration at idle? C'mon guys, just because I am not asking advice about a mod doesn't mean you can't reply! Our trucks have to be able to run good before they can look good!

 

Give people a break here we do sleep from the time of your first post and your second.

[Stevens03]

Have you cleaned your MAF and throttle body?

 

Agreed... My brother in laws 04 Denali had similar issues.. and we cleaned the throttle body and MAF sensor and it runs smooth as glass.

[salden77]

Have you cleaned your MAF and throttle body?

 

Agreed... My brother in laws 04 Denali had similar issues.. and we cleaned the throttle body and MAF sensor and it runs smooth as glass.

 

 

what do you recommend cleaning throttle body and MAF sensor with? when i put my new intake in a couple weeks ago i just wiped all the crap out of the TB with a shop rag because i wasnt sure what was safe to clean it with.

[Jennabear]

Any auto parts store will sell cans of MAF cleaner and throttle body cleaner. They explain how to clean both on the backs of the cans.

 

Since you put a new intake on there, I would check to make sure that the oil from the filter hasn't gunked up the MAF screen.

[salden77]

Any auto parts store will sell cans of MAF cleaner and throttle body cleaner. They explain how to clean both on the backs of the cans.

 

Since you put a new intake on there, I would check to make sure that the oil from the filter hasn't gunked up the MAF screen.

 

ok thanks, have one of those oil free dry filters from air raid so hopefully no more oil gunk. but when i had the old intake out i noticed my throttle body was def. gunked up with black stuff, prob. from old k&n air filter that i had for my oem air box.

[Jennabear]

Did you clean the MAF screen before putting the intake on?

[salden77]

Did you clean the MAF screen before putting the intake on?

 

i didnt touch the MAF screen because it seemed pretty fragile, just wiped the gunk out of the throttle body with a shop rag.

[Jennabear]

I would definitely hit that with some MAF cleaner then. It is fragile, but if you follow the instructions, you will be good to go.