bdeming

As the title states I'm having issues with my engine breaking up. This happens mostly under 3-3500rpms and only under a load. I have re-gapped plugs, new wires, swapped coilpacks. It's a swapped car, for grounds I have 3 on the back of the drivers head, one from alternator to frame, one from right side of block to frame. Then the battery is grounded to the rear strut tower. Good enough grounds? Also my crank sensor wires are not shielded, is this necessary? If so how can I correctly shield them? Had the car on the Dyno yesterday, all sensors were working properly, played with adding fuel/ leaning fuel. It is intermittent, one pull I made 378whp and the very next I made 295whp. Any pointers would be appreciated!

Roarin_8

iTrader: (5)

What do you mean by breaking up? What symptoms is the motor doing exactly?

bdeming

It will missfied under load, acted like it was loosing ignition to one or two cylinders.

Roarin_8

iTrader: (5)

The tuner should be able to see which cylinders are misfiring, that will help narrow it down.

bdeming

The tuner said there were no misfire codes. It acts like a bad coilpack or wires. Or just weak ignition somehow. Since I've changed all that I'm leaning towards the crank sensor wiring. Is there ever issues with the PCM?

spy2520

iTrader: (3)

there can still be misfires with no code. You can monitor the misfire count of each cylinder when logging. The count has to be over a certain threshold to throw a code.

thunderstruck507

iTrader: (18)

fully inspect the wires and plugs for burns or cracks

98cherrySS

iTrader: (2)

THIS...

Also look for any random wires that may have contacted the exhaust. Crank sensors, O2's, temp sensors, anything. It's amazing what one arcing wire is capable of. Also, make sure there is no paint where the grounds terminate into the frame.

truckdoug

iTrader: (25)

you can watch the live misfire count on the torque pro app i think

Tig

I have had a misfire in my 07 Tahoe but it has never thrown a code. I only feel it at idle, it has a little chop in the idle.
I had recently installed a new billet stall. Ever since, at lock up while cruising, it shudders. It shudders until I'm out of that sweet spot. Or, if I drive more aggressive, it does not do it at all. Soon after getting my stall, I replaced my plugs and wires. Coil packs are original and have about 155k miles on them.

I had recently brought it to another shop for a tune and while we were on the road they spotted it misfiring on cylinder 3. He suggested I replace/remove the DOD all together.
Unfortunately I have dumped more than I'd like to admit into it for pretty much a false diagnosis on the original shops behalf and cannot afford to just throw parts at it. Also cylinder 3 is not a DOD/AFM cylinder.

When do you know its time to start replacing parts because of a misfire?
I have no problem buying new coil packs, sensors, etc,,, but internal parts add up quick.

Something I noticed to is, cylinder 3 is not a DOD cylinder. Please correct me if I'm wrong, 1, 7, 4 and 6 are the AFM/DOD cylinders.

Any thoughts or recommendations would be much appreciated.
Thanks