For the last 3 months or so, I have been having an issue with my car misfiring when it goes down this one road which is pretty steep. When the car is under load going uphill at about 50/60 mph, the car will jolt, lose power, begin misfiring and the engine light will start to flash. Then after a few seconds, the engine light goes off and the electrical fault light comes on. Once I pull over and turn the car off and back on again, it returns to normal and the light stays off. I have since kept my code reader in the car and when it does it, I look at the error codes. It is always cylinder 1 or 3 misfiring. Since this started happening, I`ve changed the coil pack, plugs and injectors one after the other and nothing has resolved the issue. Everyone I`ve asked has said its the coil pack that's at fault. Is it most likely I`ve just bought a bad coil pack? (it was brand new, not used) or is there anything else that could cause these symptoms? I reluctant to buy another coil pack and I have no proof of purchase for the one I did buy. Thanks in advance, any advice is highly appreciated.