jimmypop13

iTrader: (17)

I was driving home today when my SES light started flashing and the car and shifter would shake if I touched the gas pedal. The code being thrown is Random Misfire so I used my scanner to find which cylinder was the problem and cylinders 5 and 6 appear to not even be working under load because the # of misfires just skyrockets when I accelerate. But, when I'm just sitting at idle and run a cylinder balance test, they all come up pretty close to even. That makes me think it's not wires or coil packs but could it still be those? Thanks
-Chris

Viper

iTrader: (6)

Could also be a dirty MAF or a bad O2 sensor. Without throwing the code for either. I had the same problem last year and had to replace first the O2 sensor then the MAF. Just my $.02; clean the MAF first to see if it helps.

SS101

iTrader: (2)

+1 dirty maf and old o2s can cause this problem

LS1Birdy

iTrader: (1)

Is it an auto? and when was the last time you replaced the plugs? i got a few things you could try

DaddySS

Plugs or wires are often the cause for misfire under load - check those on 5 & 6

Lt1Porsche

iTrader: (6)

I mostly agree with DaddySS. Check your plugs and wires and coil packs. They are the most common things to cause a misfire under load.

jimmypop13

iTrader: (17)

The plugs and wires were changed in July. I'm just having a hard time understanding why it didn't start running like crap until I got off the highway and then it was like an instant change when I touched the gas pedal again. The coil packs are stock so I guess I will just swap 5 and 6 with the ones next to them to see if it's the coils. The o2 sensors seemed to be working fine when I drove around yesterday with the scanner. I'll have to check the maf readings next time to see if the maf died, I just cleaned it with maf cleaner 3 weeks ago. Thanks for the help so far. I'll let ya know what I find.
-Chris

jimmyblue

iTrader: (11)

If you have excessive gap and/or an insulation fault the
spark ultimate voltage may be enough to arc against
lower cylinder pressures but not bust over a full pressure
gap (something else lets go first and you lose it). If you
have an old-timey timing light with magnetic pickup, put
that down close to the plug, tape the trigger to "on" and
lash it down to the hood pointing in your face and go for
a drive. If the light cuts out at WOT you have a gap,
wire, coil kind of problem. If the light is on solid and you
still cut out, have to look elsewhere.

jimmypop13

iTrader: (17)

I'll be able to work on my car tomorrow and check the plugs/plug wires/coil packs to see if that's whats goin wrong. Does anyone think it could be the fuel pump or injectors? They were both upgraded back in July.

LS1Birdy

iTrader: (1)

If it was the fuel pump, you would see it happen with all the cylinders at random times...at most cases with random misfires on certain cylinders under load it is the plug/wire. just try swapping the plug and wire to another cylinder and see if the misfire moves to the new cylinder. *just remember which cylinder you moved them too* if it stays the same, then swap the coil, if it still stays the same then try it with the injector.