What I mean is that the 104 engine is known to have cracked engine wiring harnesses causing lots of codes and problems. You peel back any of the insulation at the coils or at the injectors and you would inspect the insulation on the wiring itself. If its cracked, replace the harness. Also, I know that codes were pulled, but what are they? They are many codes for an O2 sensor, they are some for implausible, short to ground, lazy, they are some for the heater of the O2 and if so the relay which controls the O2 sensor. They are misfire codes which may not be caused by the plug itself. You may have a bad resistor or a bad coil which would then possibly miss on two cylinders. Engine roughness is not so common. A quick test of the intake seals and vacuum hose should find the roughness. There is a lot more about Mercedes engine from 1991 to 2001 that techs seem to not think about. Things have changed and must be checked, verified and thought about before replacing things. For instance, if a code is retrieved for a heater of the OS1, a tech sometimes replaces the O2 sensor thinking OK, that's it, but a current test is needed at the O2 when the engine is dead cold started and the heater can only draw a max of 4 Amps and very quickly decend to .500 Ma to keep it hot. If you get 4.3amps, you get a check engine light for a O2 sensor. Well, there is a relay techs forget about, so one replaces O2, and forget about the relay. One may also replace the O2 relay and not check for high current which may be caused by a bad ground on the circuit. All this seperates the boys from the men and that's why, good knowledgable techs make good money because knowledge in a system comes from education and experience. PS, I Am one of those techs in the six figures a year and I deserve every dime of it. Ps, which shop are you going to in Newport area??
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