I have a 94 Camaro3.4L V6 automatic. The engine runs fine when cold, but when it warms up it stumbles when at an idle/stopped (in drive or reverse).

Things I've done to try and remedy the problem:
* Replaced the plugs (AC)
* Replaced plug wires (autozone duralast). The originals were in bad shape.
This greatly improved the misfire/stumble but I'm wondering if the duralast
wires just don't cut it since the problem is still there.
* Had the injectors flow balanced (this has the engine running smoother)
but the problem is still there.
The Coil pack looks newer than other items in the engine compartment so I'm sure it has been replaced before.

I read the "Mystery Misfire" thread by the 3.8L owners and wondered if the 3.4 has a history of overheating the plug wires? Would the wires, sleeves, etc recommended in that thread be the place to start?

 

Did you read the plugs before you tossed 'em?

Did any of them stick out? It sure would help narrow down some problems if you remembered...

Stumbles point to vacuum leaks....which covers bad intake mani gasket. I don't want to jump that far ahead, but you see why I mentioned reading the plugs.

 

Vacuum leaks cause high idle. What happens when it warms up and you put the trans in neutral?

 

Alfred,
I looked them over but don't remember their color/wear/etc. I'll have to start recording that from now on.

The #3 plug boot was a bear to get off, I thought is was glued onto the plug. I moved the metal boot shield from #1 to the #3 to try and protect it from some of the heat. I didn't go back with any new wire sheathing.

 

FunkZ,
Warm, and in neutral, the engine idles ~100rpm higher and the stumble goes away.

 

That sounds normal, when put in drive the engine is under more load and rpms drop. When cold your idle will be higher, once it warms up, idle speed will drop.

Is the engine actually stumbling/misfiring though or are you feeling a vibration from the lower rpm?

 

FunkZ,
You can feel, hear, and see (on the tach) the stumble. It is definately misfiring.

 

coil packs are common and so is putting on autozone junk. get that stuff off of there and get some a/c delco parts ar at the least delco platinum plugs with napa belden wires. i fix so many cars today that run worse after the zone tune up but they swear it can't be the parts. you will pay more but parts are not parts. it is like saying a kia is the same as a lexus. they are both cars right. sorry my rant for the day. three cars this week i have fixed by de-autozoning it

 

Thanks Byrons, point well taken. I'll stop by Advanced and pick up some AC/Delco wires.