intial P0353 dtc code

[takoon]

Initially started running rough as if fuel blockage or dirty fuel as I’d just filled up. Sounded as if not firing on all cylinders got it home read the codes came up with a P0353, did a bit of looking around & changed the coil pack leads & plugs & also did the fuel filter. Went for test drive was still running rough when under load, read codes again this time was showing p0303/304 misfire.
Have tested coil leads pugs all fine, plugged in spark plug testers the ones u place between the lead & then onto plug, led light shows. When placed on cylinders 3 &4 led is dim, & when under load they dim even more , where as the others are very bright, Auto spark tested wiring harness from ecu to coil & to plugs all fine so its heading for injectors or ecu fault any ideas guys

[BLUETHUNDER]

You dont say what vehicle it is??

[takoon]

BLUETHUNDER said:

You dont say what vehicle it is??

suspose that would help lol its a 2001 f150 4.2lt v6 auto

[HD Adam]

Try swapping the coil packs from side to side.

If the fault then shows up as a PO301 or similar, then it's the coil packs.

If the misfire is still on 3 & 4, you could have a blocked injector. You could try swapping them round as well to pin the fault down.

[takoon]

HD Adam said:

Try swapping the coil packs from side to side.

If the fault then shows up as a PO301 or similar, then it's the coil packs.

If the misfire is still on 3 & 4, you could have a blocked injector. You could try swapping them round as well to pin the fault down.

cheers no fault with coil leads plug etc, so that was my next port of call, just a bd to get too, ah well cheaper than getting a new ecu, cheers will post results when located fault