Running Rich

[brettj]

Also, make sure you change the main EFI relay under the passenger side dash. That relay change made a big difference in my EFI system performance.

[Zagato]

Made another discovery. Looking at one of the injectors, it is very wet. The other 7 are dry, but this one is wet to the point where there is a thin film of liquid around the base. Also the heat shielding around the wiring that connects to it is soaked as well. I can't tell if it's gasoline or not because there is no strong smell.

I don't know the cylinder numbering of the engine, but viewed from the driver's seat, it's the second injector on the left bank.
Something that might be related to it, for two weeks the engine was not running right, sounded as though one of the cylinders weren't firing properly. This resulted in lack of power and sputtering exhaust when accelerating. The condition has all but disappeared now, as summer temperatures has risen.


Plus, two more questions:
-Does the condition of the exhaust system affect fuel economy? Mine is in a sorry state where all the noise is escaping from somewhere near the middle-front of the car rather than out the back.
-Will changing the fuel filters affect fuel economy and performance? I have no clue when mine were last changed. The last proper Merc dealer service was over 20,000 miles ago. Plus, stop start traffic causes the fuel pump to buzz.

Thanks!

[pez]

A fuel filter can get ruined in just one tank of bad gas, so it's always a good idea to change it, if only to rule it out of the equation.

I would suggest going thru and changing all the fuel injector seals, and performing a leak down test.  Simply pull all injectors, but leave them connected to the fuel lines. Turn the key to the run position to cause the fuel pump to run and pressurize the system. Put newspaper under the injectors to see if they are leaking. If they are, replace them.

Also, if you can get your hands on a fuel pressure tester, now would be a good time to test the pressure.  The combination of a buzzing fuel pump and poor running are possible symptoms of low fuel pressure, and hence the reason for your poor running.