air mass sensor - PeachParts Mercedes-Benz Forum

greythunder · #1 11-05-2014, 05:08 PM

I had noticed while ago that my car wasn't getting up and going like it should, and while driving 50ish miles an hour when barely any throttle input was giving the engine felt like it was miss firing. i changed all the vacuum lines and the problem went away.

today, i was taking the headlights out to "renew" the headlight doors with clear lacquer, when i noticed the air mass sensor had been unplugged since i did the vacuum lines about 3 months ago.

i promptly plugged it back in and took it for a spin thinking that the engine would be running better than ever! i was wrong. the sluggishness was back, and the missing at light throttle input at 50 was back as well.

What role does the air mass sensor play, and how could it run better with it disconnected? Is it possible it's a bad unit?

shertex · #2 11-05-2014, 05:24 PM

I didn't know the 92 300D had a MAF sensor. Can you describe the location of the part in question?

Regardless, your best best is to do the wastegate swap, of which one of the beneficial effects is to eliminate all the vacuum crap on the passenger side of the engine. It will save you all sorts of aggravation in trying to diagnose stuff like this.

engatwork · #3 11-05-2014, 05:31 PM

They do have a MAF sensor but not like the modern cars. It is a large, cumbersome mechanical device. 80s models Toyota pick ups with the 22r engine utilized the same type. They are quite pricey if you have to purchase one.

shertex · #4 11-05-2014, 05:44 PM

Quote:

Originally Posted by engatwork

They do have a MAF sensor but not like the modern cars. It is a large, cumbersome mechanical device. 80s models Toyota pick ups with the 22r engine utilized the same type. They are quite pricey if you have to purchase one.

Where is it located? I was having trouble finding it in the EPC.

greythunder · #5 11-05-2014, 06:09 PM

its circled in red, in it's currently unplugged state. i would love to ditch the rat's nest of vacuum lines, but im not too keen on drilling a tapping holes in turbos.

dieselbenz1 · #6 11-05-2014, 06:14 PM

I have the same vechile and to get boost just unplug the MAF sensor. Whit it plugged in when the eGR valve opens it he computer is looking for a reduction in MAF signal. You will do no harm with it unplugged. You may wish to change to a pressure control for the boost rather than vacuum at some point in time.

97 SL320 · #7 11-05-2014, 06:23 PM

That is a vane type air flow meter, see also Bosch L-Jetronic ( gas engines ) This tech is from the early 70's and was licensed out to other car makers.

shertex · #8 11-05-2014, 06:30 PM

Quote:

Originally Posted by greythunder

its circled in red, in it's currently unplugged state. i would love to ditch the rat's nest of vacuum lines, but im not too keen on drilling a tapping holes in turbos.

You don't need to....just run a pressure line from the intake manifold to the new wastegate.

greythunder · #9 11-05-2014, 06:49 PM

oh really? well i have to say that makes sense... where does one acquire said new waste gate?

dieselbenz1 · #10 11-05-2014, 06:56 PM

I took my vacuum actuator to a turbo shop and they gave me a new pressure actuator with the same mounting and shaft length for $10.00. You will have to find a pressure point to connect the other end to in my case I used the EGR hole on the ontake manifold and made a plate.

shertex · #11 11-05-2014, 07:33 PM

Quote:

Originally Posted by greythunder

oh really? well i have to say that makes sense... where does one acquire said new waste gate?

ATP TURBO - The Premiere Provider of Turbocharging Components is the place most of us have got it.

greythunder · #12 11-05-2014, 07:45 PM

can anyone provide a tutorial or write up?

shertex · #13 11-05-2014, 07:50 PM

Quote:

Originally Posted by greythunder

can anyone provide a tutorial or write up?

All the info you need is in the big wastegate thread....but you kind of have to piece the information together. Wastegate actuator swap for OM602.962?