Engine Stuttering/Misfire during acceleration!

[NDARYD]

Hey all,

I've been having an issue with my 04 GT for the last few weeks.

When the car is under load (accelerating) the car will stutter heaps/struggle to accelerate and misfire (can be heard from the exhaust popping). The problem keeps coming and going every few days but when it is there, it can get quite bad.

There are no error codes showing up when hooked up to the scanner.

I've taken it to two mechanics with the following results:

Mechanic 1: Said I need to replace all four coils/plugs (total cost close to $1000)

Mechanic 2: Said it can't be all four coils as an error would come up on the scanner and the platinum plugs were replaced around 3 months ago and the issue would be there constantly but cannot locate the issue. Said a possible injector issue or electrical.

Anyone had anything similar and what was the result?

[Dropz]

Things to check, resistance of your coil packs from connector 1-2 and 3-4. resistance of all your leads, take the intake off and clean out your throttle body as well as spray a can of upper engine cleaner in as per the instructions on the bottle, and lastly, check your brake light globes for loose fitment or blown globes, you should also get a mechanic to check the operation of your o2 sensor with a scan tool and the knock sensor.

[mincedmeat]

I would take the plug back out to inspect. One could be fulty.

[NDARYD]

Things to check, resistance of your coil packs from connector 1-2 and 3-4. resistance of all your leads, take the intake off and clean out your throttle body as well as spray a can of upper engine cleaner in as per the instructions on the bottle, and lastly, check your brake light globes for loose fitment or blown globes, you should also get a mechanic to check the operation of your o2 sensor with a scan tool and the knock sensor.

I will ask the mechanic to check the resistance if they haven't already done so. I shall clean the throttle body later this week and spray the upper engine cleaner as someone else suggested this to me also. What would the brake light globes have to do with this?

I would take the plug back out to inspect. One could be fulty.

The mechanic checked all the plugs and they are all fine.


I have noticed that the issue is evident when the car is warm/hot and does not happen in the morning when the car is cold. My mate said it could be coils or injectors? As it occurs when the engine is hot and that is when the resistance changes. Can anyone confirm?

[Dropz]

It could be coilpacks when they heat up.

If its only when hot it won't be brake lights, but they can effect the cruise operation, abs operation, and sometimes throttlebody motor operation as they are all linked together in the various computers to operate as accurately as possible.

[NDARYD]

It could be coilpacks when they heat up.

If its only when hot it won't be brake lights, but they can effect the cruise operation, abs operation, and sometimes throttlebody motor operation as they are all linked together in the various computers to operate as accurately as possible.

Thanks for the info mate.

Can it be ALL four coils packs/plugs that need to be replaced? Or is the mechanic wanting to do that as it's easier instead of having to try replace one coil pack and seeing how that goes and then maybe replacing the other one until the right one is located. My mate (not a mechanic but fairly mechanically smart with cars) said it can't be all four that need replacing all of a sudden, is this true?

[Dropz]

Possible but unlikely. With the engine idling unplug one coil pack, if the engine stutters reconnect it, if the engine barely changes, then that's your culprit coil pack/spark plug.

[NDARYD]

Possible but unlikely. With the engine idling unplug one coil pack, if the engine stutters reconnect it, if the engine barely changes, then that's your culprit coil pack/spark plug.

Thanks mate. Does the engine have to be dropped to remove/access the coil packs? Because the mechanic said every time they had to drop the engine to access it.

[Dropz]

Just to check you should be able to reach but to remove them you need to unbolt the engine mounts and jack up one side of the engine at a time.

[-=HaZ=-]

Reset the ECU via the OBD II interface. Its most like your AFM, which is why it doesn't show up as an CEL or Error Code.