Where is number 1 cylinder on a 2003 mustang with a 3.8L egine?

1-4-2-5-3-6

The cylinders of your engine are numbered 1-2-3 starting from the front of the engine on the passenger side. Cylinders 4-5-6, front to back, are located on the driver's side.

Flashing check engine light is due to a severe misfire in 1 or more of the cylinders. If not diagnosed and repaired quick you will ruin your catalytic converter. There are a few things what can cause this from timing to faulty coils to faulty injectors to electrical ... to name a few.

Check out number five in the photo

Odd cylinders are on the firewall side of the engine.
Number one should be near the passenger side or front of the engine.

Line up mark on main pulley with indicator, If you have a baffle over the rockers on cylinder number one, you will need to pull off that valve cover to ensure that neither valve is open- the vavle train will be resting on the heel of the cam lobes. This means cylinder number one is truly at top dead center, and distributor can be installed with the rotor in the correct location for factory designated cylinder number 1 location. ( it could fall anywhere, as long as the firing order is in the correct order- it just makes life simpler in the future.)

If one rocker or both rockers are pressing against the valve stems or followers, the engine is 180 degrees from top dead center for cylinder number one so the crankshaft must make one full revolution additional for number one to be at the timing reference top dead center for cylinder number 1 or you can simply position the distributor rotor for cylinder number 2.. This is because the crankshaft makes two full rotations for one full rotation of camshaft or distributor.

If you find you have lined up on cylinder number 2- which is 180 degrees away from cylinder number 1 in the firing order, you should have no problem if you make sure to locate number 1 in the factory designated location and use correct rotation direction when you pug the wires into the distributer cap.

First check for worn sparkplugs and if they still god then check for spark on those cylinders by pulling the sparkplug wire off and cranking the engine over.If there is no spark then replace the coil.If there is spark i would have the injectors leaned.

number 1 is the front plug in an in-line engine the number 2 plug is next in line on a "v" engine the number 2 plug is on the other side of the block but its still called number 2 cylinder left or right side!

If you look at your coil pack the terminals are numbered with the cylinder they go to. The cylinders are as follows: Passenger side of engine, closest cyl to radiator is cyl 1, then behind it is 2 and 3, drivers side of engine closest to rad is 4,5,6. Good luck!

Here is Half an answer!! The engine serial number is located on the top surface of the engine block... near the crankcase breather pipe, front-left side of the car.
Except for the information that is provided on the vehicle certification label, I am not aware of "matching numbers" on a 6 cylinder Mustang...

1/1 is upstream sensor on the number 1 cylinder side, 1/2 is the downstream of the number 1 cylinder side, 2/1 is the upstream of the number 2 cylinder side, 2/2 is the downstream of the number 2 cylinder side. Hope this helps.