Sounds like an unsolvable riddle - anything letting air into the engine wouldn't be located near the fuel pump.

Called him back and he said it's the Jetronic. Anyone have one there wanting to get rid of?

Still a bit vague. Jetronic is the name for the fuel injection system of that era, which has many parts. "Lets air into the engine" sounds like maybe the air flow meter but you need to find out more.

300 e
 

if you have an electronic distributor it very well could be your pick ip coil that tell the dist which plug to fir. fuel pressure? shorted condenser in your dist. coil could be weak. chk for a bright blue spark from the center wire to eng block, you have to disconnect it and have someone crank it for you be careful its about 40,000 volts or higher. i really suspect you coil or the thingahmajig that replaces the coil. get you a cheap manual for your car divide and conquer.

Sounds like your crank sensor is going bad.Had a car like yours with the same problem.Needs to be OHM checked when car is not running ,although some times testing and wiggling wire at same time may get bad readings.If you test when car is running fine,you may get good readings.
One end of sensor is about a foot behind pass. headlight(test end) other is behind oil filter.Use ,search,to find the answer.You will get much more info in a much shorter time.
Pretty easy to test if you have an ohm meter,cheap at sears
Good luck
Rich

Thanks I brought that up to my mechanic and he said he hadn't thought of that but is going to check on it.

But...

He also said that he knows that this part is bad. Not sure what it is. Its under the air filter housing, a sort of plunger like thing. That whole part is bad. Can anyone help with the name of that part? Thank you all so much for your help. When I get it all fixed I'll let you guys know.

Are you referring to the part that is a round disc that moves up and down? If so, that is called the Air Mass Meter...and they cost around $800 new, IIRC.

Seems like usually the electronic sensor attached to those is the problem...not the meter itself.

How does the mechanic know it is bad? If he knows it's bad why can't he say what it is? You need a part number or a picture or to look at the EPC. It sounds as if you are describing the airflow sensor, aka airflow meter. It does have a replaceable potentiometer but they are no long in production by Bosch.

I took some pictures of the part but cant put them on here because of the size limit.

How about reducing their size?

Put them on www.photobucket.com then copy/paste the IMG Code into the body of your post.

Like this:

http://i179.photobucket.com/albums/w...d/IMG_0685.jpg

You can view the part at this URL

http://s285.photobucket.com/albums/ll41/300EforERIC/?action=view&current=AirFlow.jpg

Thank you for all of your help.

By the way How would I/My Mechanic be able to tell if it was just the Potentiometer and not just the whole part?

I reread your first post again and was wondering what your most recent problem was.
Is the car shutting off and comming to a stop?
Does it start right back up?
Or is it more of a rough running problem.
Maybe replacing the parts you changed fixed some things and this is a new problem.So what is the most recent problem you are having? I ask because this site may help your mechanic fix the problem as he may not be very familiar with Mercedes fuel injection.
Thanks
Rich

After driving for a half an hour or close to that I will be going, and with no warning the RPM's just drop to idle numbers and I slowly get to idle speed then it dies, And yes it will start right back up. Which is why he thinks that it is not the crank sensor.

Had a very similar problem - turned out to be the Fuel Pump Relay - refer thread - http://www.peachparts.com/shopforum/tech-help/210262-engine-cuts-out-high-speed-only.html