i have a 1987 190e 2.6 a/t. now i'm still getting used to the workings of this thing and learning from this forum. with that being said my question is about my fuel economy has dropped to almost nothing, getting about 8 mpg. o2 sensor seems to be functional (just assuming because dash light doesn't come on), i've got a service cd and it shows an air intake temp sensor on the scoop. on my car the scoop is missing and a don't see a pigtail for where the sensor would plug into. btw i posted on parts forum for anyone that may have an air intake (from scoop to air cleaner box). but back to the point - where should i begin looking for issues. i have a good amount of hand tools and a dvom multimeter to test, but lack the "german knowledge" to diagnose. and now for something completely different, while under the hood i noticed the drivers side upper strut mount is broken, can it be replaced w/o having to compress spring? (can't find that on cd either) thanks guys!!

__________________
"NEVER UNDERESTIMATE THE POWER OF STUPID PEOPLE IN LARGE GROUPS!"

From my review of the service information, it appears that lamda equipped M103s do not have the intake air temperature sensor on the inlet duct. Being as how the lamda system fine tunes the mixture an intake air temp is not needed.

Even if your O2 sensor was dead or the lamda system was otherwise malfunctioning, I would not expect fuel economy to drop to the levels you reported.

If you have a multimeter with a duty cycle function you can check the "duty cycle", which is a test of overall lamda system function including the 02 sensor. The following web page probably gives better instructions for running this test than the service CD.

www.landiss.com/mixture.htm

The duty cycle should fluctuate at idle and 2500 and the approximate eyeball average duty cycle at the two speeds should be within ten percent of each other.

You can also remove the RH front carpet section and do a static O2 sensor test. With the engine running remove the single wire plug (which should illuminate the check engine light) and measure O2 sensor voltage. It should be over 0.45V. You can also disconnect the two wire connector - check the O2 sensor pigtail for heater continiuty and check that the harness end has system voltage.

It's best to remove the strut to replace the upper mount. Chances are the dust boot is toast and maybe the jounce bumper. It's a fairly easy task to R&I the struts. Jacking up the front of the car the car up and lowering it down on jackstands under the control arms will keep the springs compressed with front end weight while you remove the strut to replace the mount.

Duke