SL/R129: Misfire codes p0303 p0304 p0300
08-18-2013, 11:20 AM
#1
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1993 300CE 1997 SL320
Misfire codes p0303 p0304 p0300
Hi everyone,
I have a good problem with my 97 sl320 that I'm hoping I could get some help with. 10 seconds after I start the car it gets p0303, p0304 and p0300 codes. The coil and plugs have been moved to to other locations and still the same problem. I checked the injecter pulses with a led light tool and found that infectors 3 and 4 stop flashing after 10 seconds of running and of course the idle is bad with the injectors not working. I have checked each one individually to see if one injecter was holding it down, but get the same results. I cant see 2 injectors being bad at the same exact time so I didnt move them. I have unplugged the mass air flow sensor to see if it changed the problem, still the same.
Am I diagnosing this wrong? Why would I get misfire codes and then see no injector pulses? Does the ECU turn off the injectors when misfire is detected?
The car has been in the garage for 9 months not being used but started every week or so. The battery was replaced a few weeks ago.
Please help. Any help or suggestions would be appreciated!!
I have a good problem with my 97 sl320 that I'm hoping I could get some help with. 10 seconds after I start the car it gets p0303, p0304 and p0300 codes. The coil and plugs have been moved to to other locations and still the same problem. I checked the injecter pulses with a led light tool and found that infectors 3 and 4 stop flashing after 10 seconds of running and of course the idle is bad with the injectors not working. I have checked each one individually to see if one injecter was holding it down, but get the same results. I cant see 2 injectors being bad at the same exact time so I didnt move them. I have unplugged the mass air flow sensor to see if it changed the problem, still the same.
Am I diagnosing this wrong? Why would I get misfire codes and then see no injector pulses? Does the ECU turn off the injectors when misfire is detected?
The car has been in the garage for 9 months not being used but started every week or so. The battery was replaced a few weeks ago.
Please help. Any help or suggestions would be appreciated!!
08-29-2013, 12:45 PM
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C320T 4matic & 500SL
If there is a misfire, gas is not burning. Your exhaust is getting full with gas! So I think it's normal that the injector stops!
Have you checked preasure loss in the cylinders? Maybe a outlet valve closes not correct...
Have you checked preasure loss in the cylinders? Maybe a outlet valve closes not correct...
08-29-2013, 03:56 PM
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1993 300CE 1997 SL320
Hi thanks for the response.
I have not checked for any pressure loss. I have just swapped out the injectors to other cylinders, no help. I have noticed one thing. When I start the car after resetting the codes and the battery has been off overnight, it will run smoothly with no errors at idle for a while. Yesterday I tried it and it ran for 10 minutes at idle. I stepped on the gas slowly to 1200 rpm then I got the errors. Today after I swapped the injectors to cyl 1 and 2, I let it idle for 15 minutes. I was just about to step on the gas when I got the 3 errors again.
I am leaning toward the ECU as I have moved and checked everything else. I will also do a compression check on cylinders 3 and 4 tomorrow.
I have not checked for any pressure loss. I have just swapped out the injectors to other cylinders, no help. I have noticed one thing. When I start the car after resetting the codes and the battery has been off overnight, it will run smoothly with no errors at idle for a while. Yesterday I tried it and it ran for 10 minutes at idle. I stepped on the gas slowly to 1200 rpm then I got the errors. Today after I swapped the injectors to cyl 1 and 2, I let it idle for 15 minutes. I was just about to step on the gas when I got the 3 errors again.
I am leaning toward the ECU as I have moved and checked everything else. I will also do a compression check on cylinders 3 and 4 tomorrow.
