SL/R129: Error code P0300, 302 and 308
Thread Starter
Junior Member
Joined: Dec 2015
Posts: 64
Likes: 4
From: Los Angeles , Ca
2011 S63 , 1997 SL500 La costa edition (sold) 1987 560SEC (sold)
Error code P0300, 302 and 308
Hi everyone, I searched everywhere and I found some results but I'm still having this issue.
it all started when the car was lacking some power and it pulled a code I forgot which one it was but it indicated cam solenoid, so I jumped those with 12V battery and that seemed to fix the issue and code went away, in the mean time I sprayed some MAF cleaner down the MAF box (I had a hard time removing it ) .
right after that I get the codes P0300, P0302 , P0308, (misfire codes ), the car starts out fine for about a minute or two then the idle starts shaking and it check engine light comes on, did an erase and restarted same procedure , sometimes the error comes in faster , it takes longer on cold start.
after researching these codes and doing what was advised did the following so far:
changed all plugs.
swapped coils to see if code follows (it didn't)
changed fuel filter
removed MAF and cleaned the proper way this time.
Next I was gonna tackle injectors, but I'm also worried maybe I have ruined the MAF by just spraying the cleaner down the first time? although I cleaned it prooperly later, Oh and I did use CRC cleaner on both occasions.
Any thoughts?
thanks
it all started when the car was lacking some power and it pulled a code I forgot which one it was but it indicated cam solenoid, so I jumped those with 12V battery and that seemed to fix the issue and code went away, in the mean time I sprayed some MAF cleaner down the MAF box (I had a hard time removing it ) .
right after that I get the codes P0300, P0302 , P0308, (misfire codes ), the car starts out fine for about a minute or two then the idle starts shaking and it check engine light comes on, did an erase and restarted same procedure , sometimes the error comes in faster , it takes longer on cold start.
after researching these codes and doing what was advised did the following so far:
changed all plugs.
swapped coils to see if code follows (it didn't)
changed fuel filter
removed MAF and cleaned the proper way this time.
Next I was gonna tackle injectors, but I'm also worried maybe I have ruined the MAF by just spraying the cleaner down the first time? although I cleaned it prooperly later, Oh and I did use CRC cleaner on both occasions.
Any thoughts?
thanks
Junior Member
Joined: Oct 2014
Posts: 68
Likes: 6
From: Epping,NH
1998 SL500
Hope this helps
I don't think it's the MAF. You should check and or replace your fuel filter,,,, then check for a vacuum leak ... have the battery checked even if it starts the car... bad or low battery equals random misfire codes.
Good luck
Good luck
Thread Starter
Junior Member
Joined: Dec 2015
Posts: 64
Likes: 4
From: Los Angeles , Ca
2011 S63 , 1997 SL500 La costa edition (sold) 1987 560SEC (sold)
thanks
Junior Member
Joined: Oct 2014
Posts: 68
Likes: 6
From: Epping,NH
1998 SL500
Search YouTube.com for the answers to your questions. They are very helpful! I would be surprised if multiple misfires would happen to multiple injectors at the same time. You know to erase the codes before you re-check? Hook up another battery with jumper cables to check the battery. It also could be a weak fuel pump.
Regards
Regards
Last edited by sutliffe; Dec 12, 2015 at 09:04 PM.
Thread Starter
Junior Member
Joined: Dec 2015
Posts: 64
Likes: 4
From: Los Angeles , Ca
2011 S63 , 1997 SL500 La costa edition (sold) 1987 560SEC (sold)
Thanks for your suggestions I think it's the battery, which makes sense because the car sits a lot in the garage, but that's not what confirms the battery, this is what I did, I took it out yesterday and punched it a little, when I drove it hard for a couple of minutes the problem went away I parked on the side cleared the erro, started the car and took off and drove for a while nothing happens, as soon as I stopped at a light long enough to keep it on idle for a while the error came back, which meant to me that the car was running fine on alternator boost, so to confirm this theory today I parked my truck close behind and hooked up the truck battery with a jumper cable (as you suggested) measured the voltage it was maintaining over 14v constant while truck is running, started the mercedes (error was already cleared) ran fine which was usual for the first minute or so , kept it running for about 5 minutes and nothing happened, no CEL no misfiring nothing.
So on to shop for a battery , am I gonna have to take it to the mechanic to reset the ECU after exchanging the battery?
I will post results after swapping battery.
thanks again.
So on to shop for a battery , am I gonna have to take it to the mechanic to reset the ECU after exchanging the battery?
I will post results after swapping battery.
thanks again.
Thread Starter
Junior Member
Joined: Dec 2015
Posts: 64
Likes: 4
From: Los Angeles , Ca
2011 S63 , 1997 SL500 La costa edition (sold) 1987 560SEC (sold)
Well I have spoken too soon, my initial suspicion seemed to be the correct one, because I have disconnected the MAF to clean it,
the reason I took it out for a drive because I read somewhere that after you change/clean the MAF you need to reset the "self adaption value" which requires resetting of the ECU, some suggested disconnecting the battery for 5 minutes, but someone suggested to run it in idle, drive it slow, and floor it and this will get the MAF to self adapt again, and since I hate disconnecting the battery so that was what I did yesterday, apparently everything got reset after I parked it last night, because after that jumping test I forget to disconnect the jumper and try it to see if it throws the error , so I went out again and started the car, ran fine on idle no CEL , nothing, took it for about a 20 minute drive and the problem is gone. I drove freeway, streets, made many stops , nothing happen, the car is driving beautiful, I hope I'm not speaking too soon again, but if something happens I'll post again.
thanks anyway for all the suggestions
the reason I took it out for a drive because I read somewhere that after you change/clean the MAF you need to reset the "self adaption value" which requires resetting of the ECU, some suggested disconnecting the battery for 5 minutes, but someone suggested to run it in idle, drive it slow, and floor it and this will get the MAF to self adapt again, and since I hate disconnecting the battery so that was what I did yesterday, apparently everything got reset after I parked it last night, because after that jumping test I forget to disconnect the jumper and try it to see if it throws the error , so I went out again and started the car, ran fine on idle no CEL , nothing, took it for about a 20 minute drive and the problem is gone. I drove freeway, streets, made many stops , nothing happen, the car is driving beautiful, I hope I'm not speaking too soon again, but if something happens I'll post again.
thanks anyway for all the suggestions
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Member
Joined: Jul 2013
Posts: 126
Likes: 5
From: Saint Augustine, FL
1998 SL500
Harbor Freight has an affordable conductance based digital battery analyzer--now on sales for $80.
I was at first skeptical about conductance testers however having used this HF unit for over a couple years now I only seldom pull out the old 500A carbon pile "real load" tester. The digital tester is very useful if you record base values when you get a new battery and then compare current readings to the base numbers.
I caught a dying cell in a relatively new battery in my wife's '03 Highlander just before she and my daughter took off for a 1500 mile road trip--got it replaced under warranty and saved us both a lot of hassle...
I was at first skeptical about conductance testers however having used this HF unit for over a couple years now I only seldom pull out the old 500A carbon pile "real load" tester. The digital tester is very useful if you record base values when you get a new battery and then compare current readings to the base numbers.
I caught a dying cell in a relatively new battery in my wife's '03 Highlander just before she and my daughter took off for a 1500 mile road trip--got it replaced under warranty and saved us both a lot of hassle...
