My ls1 idles perfectly at 1,100 rpm, but it does shake the car a bit and not throwing any codes. My girlfriends dad is a mechanic and as soon as he got in he said it's misfiring, than when he checked it with his code reader is said multiple misfires and 1 cylinder not firing. I can't really notice it other than the car shaking a bit and the loss of power...

Is there any way to tell if all 8 are firing correctly? I have a scanner but its not throwing any cylinder codes....
The car is starting to misfire upon startup and I get a loud pop out of the exhaust.

I heard something about unhooking each coil pack until you find one where there is no difference in idle? I don't want to get shocked as they are hard to get at.

Thanks in advance

 

Don't wanna get shocked? It's like only 20k volts or so. Haha.

I don't see why your girlfriends dads scanner picks up the codes but yours does not. Check your spark plugs and see what kind of condition they're in. When was the last time the spark plug wires or coil packs were changed? Check O2 sensors. Occasionally, they'll throw a miss fire code.

 

I definitely agree on this one. When was your last tune up? Old fouled plugs and worn out wires would be the first thing I looked for.

 

With misfire problems it always a good idea to do the basic maintenance first, such as spark plugs, plug wires, air and fuel filters. If you want to see of the plugs are firing without getting zapped, you can always buy a cheap spark checker at any parts store. However, the best way to look at misfires is with an engine scope, but these are hard to find.
The scanner shows the #1 cylinder not firing and the reasons for that could be bad ignition, bad injector, or very low compression. The scanner also showed multiple misfires, which means all cylinder are misfiring at random times and the PCM can't pick out an individual one. When this happens and the ignition is up to snuff, then the most likely reason is a lean fuel mixture. In this case it is a good idea to check the fuel pressure with a FI gage..

 

Last week I changed the plugs and air filter with no difference. I inspected the wires, they are NGK's and looked pretty mint. Although it could be arching without a sign of cracks or wear.

I do need a new CTS and my IAT is throwing a code and reading at -34 degrees celcius, maybe that could be causing the random misfire? Running way too rich possibly?

What about having the car off, unplugging a single coil pack, than starting it for each cylinder to find the one that's not firing?

In my 4 banger neon the whole engine shakes if a cylinder is not firing, but with a V8 it's a lot harder for me to tell.

I have a stethascope if that would help? Ill have to check my code reader again too.

 

The scanner said a cylinder was misfiring, but don't remember which one. When I said 1 cylinder, I meant a cylinder, not #1. My bad.

I have a new fuel filter on the way, but doubt that has anything to do with the random misfires as usually the cause of a clogged filter would be to misfire under heavy load.

On my reader I can check CEL codes and do a real time scan, I think he was reading the misfiring under a realtime scan so I will check my scanner again to see if I have the codes.

For the cylinder thats misfiring, I am thinking either coil pack or wire, but how would I find out which one is my dilema..

Thank you all very much for your replys BTW!

 

Well, if your thinking its either the coil pack or a wire, id start with the wire. Coil wire should be way cheaper to swap than the coil pack itself.

 

You don't need to disconnect the actual coil just the wiring harness plug going the coil. What I usually do is feel where the wire connects to the spark plug on each wire til one feels different than the others then I investigate that cylinder.

 

I will give that a try, seems like a decent way. I think ill have the engine off while unplugging and plugging them back in though.

 

I tested each cylinder and all were fine so far, I couldnt reach the rear 2, so I will remove the EGR tube and pull the spark plug instead to see what happens. This was an easy way to test each cylinder! Thanks for the replys!