misfire code
MBWorld Fanatic!
Joined: Oct 2012
Posts: 1,427
Likes: 100
From: Florida
2002 CLK 55 AMG cabriolet Eurocharged
Is the idle quality good? 17 - 21" vacuum reading steady.
Is it possible to cross the coil primary plug ins.
If this is confirmed ok then there is a cabling/ECU problem. low inputs to ECU = low outputs to coil primary causing misfire interpretation.
Does the car run good or poor?
If the engine performs normally it is likely a bad ECU (guessing)
If the engine is sicly then you have mechanical troubleshooting to do yet.
Is it possible to cross the coil primary plug ins.
If this is confirmed ok then there is a cabling/ECU problem. low inputs to ECU = low outputs to coil primary causing misfire interpretation.
Does the car run good or poor?
If the engine performs normally it is likely a bad ECU (guessing)
If the engine is sicly then you have mechanical troubleshooting to do yet.
Last edited by GatorMB; May 22, 2014 at 01:17 AM. Reason: added content
Thread Starter
Junior Member
Joined: May 2014
Posts: 16
Likes: 0
02 clk 320
she idles fine with a slight miss,engine runs very good,hit the gas and she flies,the exhaust pipe is very sooty,would a bad cat cause the problems...thank you for your help
what could it be what could it be..when I clear the codes a minute later the cel comes right back on,I will check the cat in the morning and see if its glowing red hot
gonna go to bed now again thank you
what could it be what could it be..when I clear the codes a minute later the cel comes right back on,I will check the cat in the morning and see if its glowing red hot
gonna go to bed now again thank you
Thread Starter
Junior Member
Joined: May 2014
Posts: 16
Likes: 0
02 clk 320
bingo,cat converters are bad!!!!!!!!!!!!!!!!!!!!!
Thread Starter
Junior Member
Joined: May 2014
Posts: 16
Likes: 0
02 clk 320
Your new P0300 code indicates a Random/Multiple Cylinder Misfire Detected .
If the car is running OK, why not see if after 3 cold restarts, the CEL turns off?
Possibily after changing some coils/wires and MAF, you're still getting error codes because the previous code conditions have not been properly cleared (e.g. still stored). I know the MB STAR Diagnostic System can clear them, some generic hand readers might, or might not.
However, as mentioned above, any of the the dozen or so system sensors, used to detect/sense faults, must change from 'not ready' to 'ready'. If all is now well, after 200+ miles of driving, the 'not ready' sensors will automatically reset to 'ready'.
If not, unfortunately, misfires can be due to many conditions, having to do with proper air/fuel ratio, adaptions.......for example:
* intake leaks
* clogged fuel filter
* spark plugs (e.g. saw that you changed a couple of coils and wires, but didn't see that you changed the plugs)
* faulty oxygen sensor(s)
* faulty fuel injector(s)
* faulty catalytic converter(s)
* stuck/blocked EGR valve / passages
* burned exhaust valve
Hopefully, you can reach the prior owner to find out what maintenance service(s) have been previously done.
If the car is running OK, why not see if after 3 cold restarts, the CEL turns off?
Possibily after changing some coils/wires and MAF, you're still getting error codes because the previous code conditions have not been properly cleared (e.g. still stored). I know the MB STAR Diagnostic System can clear them, some generic hand readers might, or might not.
However, as mentioned above, any of the the dozen or so system sensors, used to detect/sense faults, must change from 'not ready' to 'ready'. If all is now well, after 200+ miles of driving, the 'not ready' sensors will automatically reset to 'ready'.
If not, unfortunately, misfires can be due to many conditions, having to do with proper air/fuel ratio, adaptions.......for example:
* intake leaks
* clogged fuel filter
* spark plugs (e.g. saw that you changed a couple of coils and wires, but didn't see that you changed the plugs)
* faulty oxygen sensor(s)
* faulty fuel injector(s)
* faulty catalytic converter(s)
* stuck/blocked EGR valve / passages
* burned exhaust valve
Hopefully, you can reach the prior owner to find out what maintenance service(s) have been previously done.
if I were to unplug a coil pack from the wire harness,what should happen
started working on my benz again today,still not right
I have replaced o2 sensors,left and right up stream,maf sensor,cps,and fuel filter with no luck......
