Need Help Diagnosing Poor Running
 

Took the Vette out tonight to go to the gym. It sounded funny, and was WAY down on power. I'm guessing a couple, maybe few cylinders are not firing. However, the check engine light did not come one. If so the cylinders in question are either not getting spark or fuel, or both. For those who don't know my Vette, it's a Frankstein H&C LSx motor setup basically like a 2001 F Body.

Id check the plug wires.

Same here. This is the same issue I just went through with the Cobra. Check to make sure that none of the wires are sitting on the exhaust. Another way to check if the plug wires are arcing is to get a spray bottle and fill it with water. Pull your car in the garage where it's a little darker and lightly spray water mist near the wires. If any are bad you'll see the spark arc through the mist.

If the wires are fine pull the plugs and make sure the porcelain looks good. When we were putting the 383 in Phil's Jimmy we had one plug that the porcelain was loose and it was arcing causing a misfire. You couldn't tell it was loose by looking at it but when you held it you could feel it.

Thanks guys. I'll check this out tomorrow afternoon and report back.

Paul said two other possibilities would be a bad coil pack, or clogged cats.

The packs and cats came off fairly high mileage cars, so definitely a possibility. I wondered about that too. :huh:

It would be nice if you could get a CEL to help narrow things down to a single cylinder, or two. Also, Id check your fuel pressure. Maybe your not misfiring, maybe starving your engine of fuel and/or air? My GTO was running like crap without a CEL (bad fuel pump), so I went on the freeway and put the petal to the floor until I got a CEL. Granted mine is under warranty still, so that may be an iffy way to pop a CEL light for you.

I think I remember you saying you use an octane booster. Octane booster has been known to foul plugs. You might wanna pull your plugs and check them.

Well, what do you think? Click on pic for gory details. I only pulled No. 1.



Plug wires themselves are pristine, are not in contact with exhaust and have heat shields to boot. These plugs only have only about 9,000 miles them from when the motor was put together. This includes tuning period which included many gnalry AFR passes. And yes, I run a small amount of Torco, Mach Fuel Accelerator.

These were not cheap plugs, AC Delco Iridium.

I would bet that is your octane booster causing that.