Another misfire

[2000MustangGT17]

I have a 2000 GT. The check engine light comes on so I take it to Auto Zone and it said I had a misfire in no. 4 cylinder. While I was there I replaced the plugs. I took it to Ford and told them what I already knew and they said I had a bad COP. They replaced it. My coolant light was on as well. They did nothing about that. So, it ran a little better and then 2 days ago I start my car it sounded weird and while I was driving the check engine light starts flashing. I went and got brand new plugs some fuel injector cleaner and it ran great but the light was still on and now it's a misfire in no. 3 cylinder. Okay well I think if it was the COP then the test would have blown 2 codes P0303(cylinder misfire) and P0353(ignition coil no. 3 primary circuit fault,) right? I honestly feel that a crack in the manifold has caused a leak into the cylinders and could also be the blame of why the coolant light stays on. Please help

[SpectorV]

It could be, ford fixed an issue with the intake cracking after 96 but it can still happen.

[SaleenFiend]

Coil Packs fail back to back all the time. I'll see a truck in the shop monday for #1 and sometimes the truck is back the next day for #5 & #8. It happens.

But I would have the manifold checked as there is a possibility.

[2000MustangGT17]

Ok well all COP's were new. This is a plastic manifold too. The reason I think this is because I pulled the spark plug out and it had't even ignited. To me, this tells me there has to be a leak/crack in the manifold. I know the recalled plastic manifolds in 96, why would they not recall the 2000? I went on Ford website for recalls and there isn't one for my car.

[modular2valve]

in late 96 after there were numerous people bringing the mustangs back for cracked intakes, ford revised the design by intergrating an aluminum crossover in the front. the "new" design carried over from the non pi version to the pi design in 99, but all 2v intakes are plastic with the new design adding an aluminum crossover. its not an everyday occurrance to see the late design crack, but the f bodies were running plastic intakes and pretty much had the same problem.

[jimmy_beaner]

I had COP issues... I ended up replacing all 8 with aftermarket COP's. If you're interested, I have a used set of WeaponX COP's you could purchase sorta cheap (cost of 3 COP's new :-P). My issue was water getting on top of the heads and finding its way to the COP's and shorting them out.

Here's a test for you, take the "bad COP's" and switch it with another COP from a working cylinder. If the misfire switches to the new cylinder, you know it's the COP. If it stays with the cylinder, you know it's a problem in that cylinder.