Mis-fire of sorts

[zieg85]

Is there any condition that would cause a 2001 Silverado 2500HD 6.0L to mis-fire on acceleration but not turn on the check engine light?  I just took a 760 mile round trip yesterday and had this issue. Pleased that it ran fine other than that and I got 17 mpg on the Turnpike 

[Irish_Alley]

i know my buddys will do that just idling. even after a tune up. idk why or how but i would like to know also

[zieg85]

i know my buddys will do that just idling. even after a tune up. idk why or how but i would like to know also

My initial thoughts are a dirty injector cause I am pretty sure if a coil pack, bad spark plug wire or plug would turn the check engine light on.

[LTZ C20]

The ECM has to register at least a large number of miss-fires in a row, usually at least 100 before it will set a code for a miss fire. Also, a code has to set twice in the ECM before it will turn on the SES light. The reason for the number of miss fires before a code trigger is to allow the computer to compensate for possibly irregularities in fuel grade and quality, pinging or rapid changes in ignition timing due to multiple chances in engine load in short period of time.

How curtain are you that the engine was miss firing? Did you have a diagnostic computer hooked up and viewing the miss fire count in real time or did it eventually set a code for a miss fire?

[timthescarrd]

Like LTZ said, an occasional misfire won't always set the light, especially if it's only happing under certain conditions. 

When I first got my 2000 Camaro it has a misfire that would only present when idling and caused some hot start issues (once in a great while it would pend a P0300 or P0302 code but usually no light)  Turned out to be the Fuel Pressure Regulator was bad, allowed gas into the MAP sensor vacuum line causing rich condition on bank 2.

And I worked on a v6 that would misfire under acceleration because the tip of one of the coil packs had rusted.  I would start with checking for any pending codes in the ECM, then a quick check of the ignition and fuel system.

[Stewart G Griffin]

Is the battery secure?   Along with battery connections and are the battery cables good?

[zieg85]

Like LTZ said, an occasional misfire won't always set the light, especially if it's only happing under certain conditions. 

When I first got my 2000 Camaro it has a misfire that would only present when idling and caused some hot start issues (once in a great while it would pend a P0300 or P0302 code but usually no light)  Turned out to be the Fuel Pressure Regulator was bad, allowed gas into the MAP sensor vacuum line causing rich condition on bank 2.

And I worked on a v6 that would misfire under acceleration because the tip of one of the coil packs had rusted.  I would start with checking for any pending codes in the ECM, then a quick check of the ignition and fuel system.

The ECM has to register at least a large number of miss-fires in a row, usually at least 100 before it will set a code for a miss fire. Also, a code has to set twice in the ECM before it will turn on the SES light. The reason for the number of miss fires before a code trigger is to allow the computer to compensate for possibly irregularities in fuel grade and quality, pinging or rapid changes in ignition timing due to multiple chances in engine load in short period of time.

How curtain are you that the engine was miss firing? Did you have a diagnostic computer hooked up and viewing the miss fire count in real time or did it eventually set a code for a miss fire?

Thanks for the info, I'll hook up my code reader when I get home and see what it says.  I can get it to do it every time but if I drive easy and can avoid it. 

[zieg85]

Is the battery secure?   Along with battery connections and are the battery cables good?

Yes everything seems to be correct and in good shape as far as I can tell.

[LTZ C20]

When was the last time it had a tune up? What grade and quality of fuel do you use? Has it ever had a fuel injection systems service?

[zieg85]

When was the last time it had a tune up? What grade and quality of fuel do you use? Has it ever had a fuel injection systems service?

no idea on the tune up, or fuel injection systems service, I've had the truck about 6 months.  I use regular unleaded 87 octane, never use cut right stations.  123K on the odometer so it may the original plugs in it for all I know.  For the most part it runs fantastic and very quick for such a heavy truck.  If I drive it like a granny, it's fine.  If I run it harder than I should, like getting up to 55 in a hurry (from a country road to a state road) it is flawless.  If I take it easy and shift early, not lugging it and try to give it more go pedal that is when you notice it...  Probably needs a good going over and I should at least pull a spark plug to judge their condition but I haven't yet.  I am 300 miles from my tools anyway.  Truck gets 16-17 mpg so I don't think much is wrong with it.

[VileZambonie]

Just because the MIL is not illuminated does not mean that it is not recognizing the misfire. If you have scan tool check for pending DTC's or use mode $06 data to see if you can at least get an idea of which cylinder is the culprit.

[zieg85]

Just because the MIL is not illuminated does not mean that it is not recognizing the misfire. If you have scan tool check for pending DTC's or use mode $06 data to see if you can at least get an idea of which cylinder is the culprit.

I didn't realize there was a record kept of pending DTC's.  I'll plug in the scan tool when I get back home this weekend

[LTZ C20]

Yes, codes will be pending before they set hard and if thy set and then pass again and the light turns off thwy will be stored in the history until they again current or are cleared/erased.

Honestly if it was me, not knowing the tune up history. I would replace the plugs and wires, using GM parts of course, clean the throttle body and service the fuel injection system. Or take it to a dealer and just have it done.

I would also switch to a mid or high grade, like 89 or 91 octane and from a station that is top tier. I switched to 91 top tier from 87 top tier few years back when I did the first new engine and I have noticed a difference. It's all I use know, top tier, 91 octane detergent fuel. In these engines you can experience drivability issues with poor quality fuels, I've seen it many times.

[zieg85]

Just because the MIL is not illuminated does not mean that it is not recognizing the misfire. If you have scan tool check for pending DTC's or use mode $06 data to see if you can at least get an idea of which cylinder is the culprit.

nothing pending

[LTZ C20]

Just out of curiosity, what scan tool did you use? Make and model?