So I have been replacing many components on my M3, I took off the intake manifold and replaced anything from the starter, vacuum lines. All that being said, I start her up and she is running fine, but since she had been sitting for a couple months I decided that a fuel system cleaning was in order. After putting in the fuel system cleaner and driving it to the gas station (without an issue) I filled her up. After starting up after the fuel up I have a check engine light and a misfire on cylinder 4. I suspect that it is probably a clogged injector as a result of the fuel system cleaner but I just wanted to check with others and see what you all thought.
Last edited by Bushytails; 09-18-2018 at 02:07 PM.
I doubt the ordinary fuel system cleaner that goes in the gas tank would hurt anything, though I know the red line stuff I use occasionally says to use on an empty tank at the gas station and then fill it up so it mixes.
Is the misfire continuing and actually occurring, or is it just the CEL? If a cylinder is misfiring the car will run but it will be rough and noticeably down on power.
Assuming you confirm the misfire is actually happening, the most likely cause is probably an ignition coil. You can swap the cylinder 4 coil with another cylinder and see if the error code changes to confirm. If so, replace the coil. If not, move on to the plugs and injectors and do the same thing.
1999 M3/2/5 - Titanium Silver - Track/Weekend Toy
Thanks! Yeah, I am going to try that when I get home. However, I have a feeling that it is my camshaft position sensor gone bad, as I am having issues with the car starting and the car idles really rough. However, the misfire is constant and you can even feel it misfire and bog down as you wind out the engine.
Last edited by Bushytails; 09-19-2018 at 12:04 PM.
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