Is there a single component that can be the cause all 6 plugs to misfire?

[SL2 Ride]

2007 Saturn Vue 3.5

I had a mechanic run a diagnostic on it, and he said there was erratic misfiring on all 6 cylinders.

Is there one component that can cause this?
Is it possible for all 6 coil packs to be bad?

[fdryer]

It isn't likely for all six individual plug coils to fail all at once or even intermittently. There are error codes to point to individual coil failure. If every coil acts intermittently then it may point to coil wiring or ecm. And if going along this line of thought then injectors should be considered too. Not likely coils or injectors. Injectors might be considered if crap fuel is used in more than one tank fill. Ecm? Maybe but that's getting ahead of diagnosing this problem without GMs scantool for advanced diagnostics generic readers aren't capable of.

Some areas to consider common to general misfiring; loss of compression, valve timing, maf sensor, and fuel pressure.

[SL2 Ride]

Originally Posted by fdryer

It isn't likely for all six individual plug coils to fail all at once or even intermittently. There are error codes to point to individual coil failure. If every coil acts intermittently then it may point to coil wiring or ecm. And if going along this line of thought then injectors should be considered too. Not likely coils or injectors. Injectors might be considered if crap fuel is used in more than one tank fill. Ecm? Maybe but that's getting ahead of diagnosing this problem without GMs scantool for advanced diagnostics generic readers aren't capable of.

Some areas to consider common to general misfiring; loss of compression, valve timing, maf sensor, and fuel pressure.

ok, this has gotten weirder. the Vue only has 80k miles, but I figured what the heck, i'll get the plugs changed. the plugs that came off it weren't original denso plugs. someone had swapped them out with ac/delco's.
so the motor runs smooth now. BUT... now I have both the large and small evap codes being thrown.
is there something a mechanic could mess up just from changing plugs that would throw those two codes?
oh and I should probably mention, I had him inspect the timing belt, which requires the caps at the end of the cams to be pulled, right?

[fdryer]

I'm not familiar with 3.5L Vues so cannot comment on timing belt inspection procedures. With a twelve year old Vue and less than 100k miles on it, the evap codes may be age and/or corrosion related. Live in the salt belt? Mechanic new to you? If spark plugs were not replaced with recommended plugs, going off on a whim or hearsay can sometimes create new problems.

[SL2 Ride]

Originally Posted by fdryer

I'm not familiar with 3.5L Vues so cannot comment on timing belt inspection procedures. With a twelve year old Vue and less than 100k miles on it, the evap codes may be age and/or corrosion related. Live in the salt belt? Mechanic new to you? If spark plugs were not replaced with recommended plugs, going off on a whim or hearsay can sometimes create new problems.

plugs were correct iridium denso's.
the Vue is from Florida. I drove it here about a month ago.
when I took it to the mechanic, there were no codes being thrown.
mechanic is new, but a lot of people from where I work use him, as he is across the street from us.
coincidences happen, but there were no codes when I dropped it off at the mechanic's garage, and two when I picked it up.

[SL2 Ride]

so I took it to GM to get it checked for misfires, etc.
they said there was a very minor history of it, but that the new plugs had solved the problem.
it sucks that I had to pay twice for the scan, but whatever, it's ok now.
I replaced the gas cap, which cleared the big and small evap code.