Question about 1997 Mercedes-Benz E-Class
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P0308 OBD II Trouble Code
Trouble shooting misfire Code P0300 P0301 P0302 P0303 P0304 P0305 P0306...
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Posted on Apr 13, 2015
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Posted on Jan 02, 2017
SOURCE: 96 bmw 740il misfire
This is a pretty common problem. I would change your valve cover gaskets. They run around ~ 50 bucks. If they are bad it will leak oil into spark plug well and cause a misfire. Very known on the 740.. Also if tune was not anytime not too long ago id change spark plugs while you at it. Then clear the computer and if you still get misfire on 8 try changing the ignition coil which is right about the cylinder with cylinder ignition coil 5. clear the computer. if you get random misfire and misfire cyclinder 5 after then its your ignition coil. parts store runs around 100 bucks
Posted on May 04, 2009
Fuel injector cleaner commonly has a low success
rate, and will not help if it's more than one cylinder that is
missfiring. The fact that you have a "rattle" noise, leads me to beleive
the engine is not receiving fuel on one or more cylidners. If it is all
the cylinders, than the fuel pump may be the culprit, or the fuel pump
circuit. But if only one cylidner is missfiring than it is a possibly an
injector. A code P0300 refers to all cylinder missfires, and any code
between P0301-P0308 distinugiushes a particular cylinder.
1- a general electrical tune-up (spark plugs, wire set, cap & rotor) is a basic start to cure this issue. Wiggle the dist shaft while you are in there, if you have one.
2- Then a good carbon cleaning / throttle-body cleaning.
3- Vacuum leaks at any of the hoses that connect to the Intake manifold; especially the MAP sensor connection.
4- If that does not help then the O2 sensor could be bad or drifting.
5- Funky coil/coil-packs
6- Theoretically a microsecond glitch in either the cam or crank shaft sensors would cause this, but I am not aware of this as a typical cause.
7- Lastly a funky PCM but again it is not common for this to cause miss-firing.
Note for the V8 then also:
a) bad erg valve (this dilutes the combustion gases and hence raises the combustion temp
b) a leaky plenum/Intake manifold gasket. Leaking Intake gasket symptoms
Also can check the TSB 18-48-98 Ignition System Cross Fire/Secondary Ignition Wire Induction (Complete Version )
Hope help with this (remember rated this). Good luck and have a nice day.
Posted on Mar 05, 2010
The check engine light, driving problems and smell was in consequence of the misfires. If now the car drives fine, the vacuum leak could have been the cause of the original troubles. As far as I understood now the problem is only when idle.
Ensure that you have replaced the air filter , also double check vacuum and check/clean the air intake duct and sensors (IAT, MAP- see here for removal). Those are factors that can affect and cause misfire during idle. The IAC valve can also cause similar troubles and must be checked.
All the part listed above may cause lean or rich mixture. The problem is not necessarily detected by the O2 sensors in the exhaust and may result in no lean or rich code being stored in ECM.
If mixture and air intake are not responsible, and if the problem does not only occurr when idle, check the high voltage wires from coils to spark plugs (particularly if a code on a particular cylinder comes back). Check timing, valves, EGR and fuel pressure/fuel pump. Try doing an injector cleaning and check injectors (both spray and voltage).
Posted on Dec 20, 2010
So your codes are: Multiple random plus misfires on 1,4,8. Misfire during startup, and ignition coil E (cyl 5) primary or secondary circuit malfunction.
You said that four new coils were installed. Perhaps the coil to spark plug order and the firing order have been scrambled. The spark plug wires may be old and leaky--especially if they are the originals from 2003. You could have a vacuum leak into the intake manifold, the EGR valve could be sticking open when it should be closed, the fuel filter could be clogged, the fuel pump pressure could be too low or stuck at the idle setting, the fuel injectors could be dirty, and cylinder compression could be low (putting on the wrong size o-rings when reinstalling injectors will prevent proper compression.)
Posted on Feb 10, 2011
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