RPM's dip at idle and truck sputters on acceleration!

[Rgilbert]

My 2008 4.3L silverado has been running rough the past few weeks, at idle the RPM's dip and the truck shakes every 10-20 seconds then returns to normal. When accelerating it jolts and sputters till it catches up then runs like normal above 1500 rpm's...What do y'all think could be the reason??

[Scotty-D]

Is the service engine soon light on? If so, does it blink when it's sputtering, and then quit blinking when it picks up?
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[BigDan3131]

How many miles are on it? Its either the fuel pump or the coil.

[Rgilbert]

One time when the problem first started the check engine light flashed about 5 or 6 times then went off and hasn't flashed again. There are only 41,000 miles on it.

[72chevyk10]

i would say one of the plugs went bad or are not firing

[storm9c1]

Agree. A flashing CEL (service engine soon light) usually means ignition misfire detected. Have the codes scanned. Chances are the codes will even tell you what cylinder was misfiring.

[Rgilbert]

If it was a misfire why does it still run bad, like what is causing it? And how would the misfire problem get fixed?

[Rgilbert]

I talked to a friend who is a mechanic and he said his truck was doing the same thing but it was from carbon build up in the throttle body...could this be a possibility?

[storm9c1]

Originally Posted by Rgilbert

I talked to a friend who is a mechanic and he said his truck was doing the same thing but it was from carbon build up in the throttle body...could this be a possibility?

Could be. Wouldn't hurt to spray it out with throttle body cleaner and/or use some Seafoam.

However, if CEL was flashing, that's an ignition system misfire -- something with the plugs/wires/coil, etc. Have the codes scanned by a parts store and see. No need to guess when your computer may tell you exactly what is wrong.

[72chevyk10]

Originally Posted by Rgilbert

If it was a misfire why does it still run bad, like what is causing it? And how would the misfire problem get fixed?

if a v8 is only runing on 7 you will always feel that "miss". my dads truck had a cracked spark plug that drove me and him crazy for a few months. would do exactly as you describe. test: plugs, wires, cap, and coil. and like storm said, a computer will probly tell you which cylinder is misfiring, if it is..

[Scotty-D]

There are quite a few completely different things that will make it missfire. Like posted above, you will have to pull up the engine codes to see what you are dealing with.

With the sputtering at low rpm that you are describing, it sounds alot like a random multiple missfire to me. The only way to know for sure is to have it scanned and see what code(s) its throwing.

[Rgilbert]

I will definitely see what codes it threw thanks for the help guys!

[bwood]

I may be wrong, but a flashing CEL is an indication that the PCM believes that damage is being done to the emission system (cat). This could be a misfire, poor or out of range O2 sensor signals, ect. Go by Autozone and have them check the codes for free then post them. I would check fuel pressure and make sure it is around the 60 psi range. I believe the V6 in your truck has had the same Vortec injection system since 96, they require 60-63 psi of fuel pressure. Also check the condition of the cap an rotor, 41k isn't many miles but it is 5 yrs old. Over time, the cap contacts corrode and cause similar issues.

[badpontiacs]

I believe there is a special policy for that. Take it to the dealer or give me your VIN in a pm and i can run it to see if it applies. I am a GM tech at a local Chevy dealer.