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CarDoc
CarDoc, Auto Mechanic
Category: Car
Satisfied Customers: 625
Experience:  IMI L3 Motor Vehicle Mechanic
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I have a 114i BMW on a 2013. New timing chain after snapped

Customer Question

I have a 114i BMW on a 2013.New timing chain after snapped chain and now it misfires at idle after head rebuild and new timing chain.
Submitted: 7 days ago.
Category: Car
Expert:  CarDoc replied 7 days ago.

Hi, How are you?
I'm Shabaz, one of the automotive experts, I'm sorry you're experiencing problems with your car, I will do my best to help you today.

Is the misfire on one cylinder?

Customer: replied 7 days ago.
its cylinder 1
Customer: replied 7 days ago.
I have had the ecu tested and it came back fine with no faults
Customer: replied 7 days ago.
I have swapped injectors and swapped coils but fault remains on cylinder 1
Customer: replied 7 days ago.
It has new plugs too
Customer: replied 7 days ago.
All cylinders have same compression
Customer: replied 7 days ago.
Drives perfect just shakes and misfires at idle
Customer: replied 7 days ago.
These are the faults
Expert:  CarDoc replied 7 days ago.

Have you removed the spark plug from the cylinder and checked to see if there is a spark there on crank?

Remove the fuel pump relay/fuse, remove spark plug from cylinder 1, connect the coil plug, rest the tip of the spark plug on a metal surface so there is a path to ground to prevent any damage and crank the engine.

Customer: replied 7 days ago.
I wil have to give that a try once the ECU is back from testing
Customer: replied 7 days ago.
I think we did try it but can remember
Expert:  CarDoc replied 7 days ago.

It best to check the actual spark because there could be an issue with the wiring rather than the plug. You also need to check if you have power to the injector on cylinder 1, it's best to use a 12v test lamp so you can see the pulsing from the injector connector.

I hope this helps.

Customer: replied 7 days ago.
I will give it a try on Friday and get back to you
Expert:  CarDoc replied 7 days ago.

Ok, you can message back on here and I will get back to you asap. Thank you

Customer: replied 7 days ago.
Thanks
Expert:  CarDoc replied 7 days ago.

Welcome

Customer: replied 6 days ago.
I have tested it and I am getting a spark
Customer: replied 6 days ago.
Cant get to injectors as they under the inlet manifold
Expert:  CarDoc replied 6 days ago.

If you can get to the injector connector, you can back probe the wire with a paper clip and then use a test light to see if you get a voltage pulse. Injectors are ground side switched, which means that the ECU controls the ground so, that's the wire you need to back probe.

Customer: replied 6 days ago.
Tried that and injectors are powering up
Customer: replied 6 days ago.
pulsing
Expert:  CarDoc replied 6 days ago.

The car will have to be diagnosed electrically using an oscilloscope. An auto electrician will be able to check the injector timing, ignition timing, crankshaft+camshaft correalation all on one computer screen and any timing issues will become obvious very quickly. It seems to be a timing issue, even if the belt has jumped one tooth on the cam sprocket, it will cause issues like this.