low idle stumble

[Tbruz]

Greetings,
2004 5.3L with 105K miles.
Just had new Delco Irridium plugs and non Delco plug wires installed.
I can feel an occasional low idle stumble when starting from at a complete stop; gentle application of throttle make it worse; stutters and stumbles but then its fine.
Idle perfectly in park or neutral.
No codes showing, yet.
Any ideas appreciated; Bad coil pack? Bad MAS?
Thanks in advance.
Tbruz

 

[Rivieraracing]

Was the stumble there before you replaces the plugs and wires? If so, try cleaning out your throttle body, they get dirty pretty quick and it's a pretty easy and cheap fix for most!

 

[jplinville]

Try a Seafoam treatment...it always works for me. Do the intake, it will thank you for it...

 

[Tbruz]

Stumble was not their before plug/plug wire change.
Started about 1 week ot 400 miles later.
Doesn't feel as "peppy" right now either.
Thanks
Tbruz

 

[Copland]

Sounds like a misfire. I could be a bad wire or a bad plug. I've had a bad plug with a little crack in the insulator. You almost couldn't see it but it caused to plug for not working properly. Maybe you should first try to swap the wires back to your old ones, if you still have them, and see if it still stumples one a takeoff. If that doesn't work try the same with the plugs. If this hasn't been before, the culprit will be very likely one of your new plugs or wires...

You won't notice a misfiring cylinder at idle, but when you put some load on the engine then you have these symptoms you've described.

 

[Tbruz]

Throttle body cleaning did the trick!
Idle is smooth and steady, no stumble under load.
Thanks

 

[Rivieraracing]

Glad to hear that it worked!!

 

[Vinniety]

Throttle body cleaning did the trick!
Idle is smooth and steady, no stumble under load.
Thanks

Read up on the seafoam treatment as well. I did throttle cleaning and the seafoam through brake booster and i couldnt believe what a difference it did. I also add a can of seafoam to the gas once every few months.