Thats what my car is throwing.

I have changed the plugs a few times and it is still there. I also changed the wires & still there. I had it scanned at Autozone & the scanner did not say which cylinder(s).

I can feel the car is down on power, but at 70+ it'll shake pretty bad.

I know the wires are all on properly and the plugs are good. That leaves coil packs & what else?

Anyone in South NJ with software that says which cylinder(s) it is want to help?

 

Mine was a loose plug wire. Make sure they're all on thight

 

.....

 

Do you have an aftermarket cam? This will trigger the P0300 (random misfire as well).

 

i just got thru this. mine was missing alot it turned out to be the o2 sensor

 

No, see my mod list.

 

It misfired b/c of an o2 sensor?! Why wouldn't it just throw the o2 code?

 

Mine happened to be 2 rocker arms loose from a installed improperly from a speed shop.

 

Anymore input before I just spend $ on an o2?

 

How many misfire are you getting on average? and the count of misfire when it does miss.. Mine doesn't throw a code anymore but it get like 3-10 misfire on ocassion. Not sure if that's normal or not.

 

I don't know how many. It shakes like a bitch at 70+

 

I think you would need to get yourself or have someone with a HP Tuner or EFI Live to scan which cylinder is misfiring and start from there. Otherwise you would need to blindly with a regular OBD2 scanner go see what the code brings and fix one thing at a time but that might also means replacing the item that's not causing the problem.

When I had a bad misfire it threw a random misfire code but my real time scanner keep showing cylinder 1 as the misfire and not a random misfire on all 8 cylinders, and after changing out coil pack, spark plug & wires with another cylinder (#3) it still showed cylinder one and by that time it had a bad tick to the valvetrain so I took the coil packs off and valve cover to find the problem of my misfire which was a mechanical issue. Hope that helps.

 

You'll know if you have a bad O2 by looking at the plugs. When my O2 went out my idle and part throttle running was extremely rough. Pulled the plugs and the entire passenger side were completely black.

Turns out when the O2 took a dump it read low voltage or lean. PCM reacted by dumping fuel into the passenger bank.

 

I've changed the plugs a few times & they always looked good.

 

If that's the case, I'd pull the valve covers and look for a broken spring, bent pushrod etc.

 

My money is on a bad O2 sensor. When my O2 went out, threw random misfire codes also. I bet it's an O2

 

I had my car on HP tuners live and it showed that my o2's were on there way out and my car would miss fire. It really got bad when it was raining I don't know what the rain had to do with it but it got bad. I changed the o2's havent had a problem since.

 

Are you sure both banks are firing?

 

When is the last time you cleaned the MAF? Have to ask
this every time I see K&N filter in the mods list.

 

I checked that out while I was under there. It's clean.

50 miles after I put in a new o2 & reset the PCM. No SES light yet, but the shake at 70+ is still there