C-Class (W203) 2001-2007, C160, C180, C200, C220, C230, C240, C270, C280, C300, C320, C230K, C350, Coupe

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Old Nov 20, 2019 | 11:57 PM
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W203 c240 2002
HELP!!!

My 2002 c240 160000 miles has a misfire on cylinder 4 i tested all injectors with noid light they all show light on and off so they all work and get current but as soon as i step on gas on park and rev up to 4 rpms or drive up to 40 mph my CEL comes on misfire cylinder 4 so i checked before like i said with noid light it works and after the misfire i checked with noid light again and injector for cyli der 4 is not firing light wont come on so it works when i reset CEL but as soon as i rev up to 4 rpms CEL comes back any ideas if my ECU is bad?
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Old Nov 21, 2019 | 01:25 AM
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C320
Sparkplugs?
Plug wires?
Ignition coils?
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Old Nov 21, 2019 | 11:46 AM
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W203 c240 2002
Originally Posted by tjts1
Sparkplugs?
Plug wires?
Ignition coils?
all new i get spark aswell
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Old Nov 21, 2019 | 11:48 AM
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What brand wires, coils did you get. What sparkplug part number?
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Old Nov 21, 2019 | 12:26 PM
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W203 c240 2002
Originally Posted by tjts1
What brand wires, coils did you get. What sparkplug part number?
idk number but i got all original from orilleys all cylinders work except number 4 when i rev up to 4 rpm CEL comes on and with noid light my injector was working before reving but after revimg when CEL comes on it shuts off injector im gonna go see if it shuts off spark to my cylinder aswell and let you know

Last edited by Chris209; Nov 21, 2019 at 12:35 PM.
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Old Nov 21, 2019 | 02:01 PM
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Originally Posted by Chris209
idk number but i got all original from orilleys all cylinders work except number 4 when i rev up to 4 rpm CEL comes on and with noid light my injector was working before reving but after revimg when CEL comes on it shuts off injector im gonna go see if it shuts off spark to my cylinder aswell and let you know
Did did you read codes? It's shutting off the injector to protect the catalytic converter because your spark plug isn't firing. Check the connection between the wiring harness and ignition coils.
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Old Nov 21, 2019 | 07:31 PM
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W203 c240 2002
Originally Posted by tjts1
Did did you read codes? It's shutting off the injector to protect the catalytic converter because your spark plug isn't firing. Check the connection between the wiring harness and ignition coils.
I took off my cats and the car drives fine no misfire code p0304 anymore
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Old Nov 22, 2019 | 06:28 AM
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w203 , w204
First swap the coil from 4 to 3 turn on the motor that's it for the misfire goes to number three cylinder and then the fault is the coil.

If the misfire stays on number for them swap the spark plug from number 4 to number 3 cylinder.

If the misfire goes to number 3 cylinder then the faults in the spark plug if the misfire stays on number 4 cylinder then swap the injectors from 4 to 3 cyclinders.

If the misfire goes to number 3 cylinder replace the injectors however if it still stays on number 4 you have either an ECU problem wiring harness problem or the valves are carbon up.

Let us know how go
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Old Nov 22, 2019 | 02:13 PM
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W203 c240 2002
Originally Posted by Craig Bastian
First swap the coil from 4 to 3 turn on the motor that's it for the misfire goes to number three cylinder and then the fault is the coil.

If the misfire stays on number for them swap the spark plug from number 4 to number 3 cylinder.

If the misfire goes to number 3 cylinder then the faults in the spark plug if the misfire stays on number 4 cylinder then swap the injectors from 4 to 3 cyclinders.

If the misfire goes to number 3 cylinder replace the injectors however if it still stays on number 4 you have either an ECU problem wiring harness problem or the valves are carbon up.

Let us know how go
I did exactly that and it kept staying at cylinder 4 but my cats were bad rattling so i took them off drove for a bit now car works no misfire
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