I have a 1991 240 dl about 200,000miles, and I was driving up a good size about hill 75mph and the car started studder like i lost all my gas. I check my fuses and found my fuel pump fuse was just about rotted out on the end terminal connection, so i figured I found the problem replaced the fuse and drove home. next morning go to go work, car is not running good idleing bad and the check engine light comes.. So I don't drive it to work. I check the code 1 2 1 Mass air sensor.. But I have been driving the car around for few days and no more issues. does anyone know the normall life span of a mass air sensor? and does this sound typical of mass air flow failure syptoms?

 

The air mass meter (AMM) has a limp home mode. With the car off, disconnect the AMM and see if the car starts and runs. If there is little to no change in the running, then certainly it could be your issue. If the car runs like total crap w/ the AMM disconnected, then look elsewhere. The AMM has a long life time typically but at 200k you could certainly be in the market for one. Yo can remove it and gently clean the inside elements. Electronic parts cleaner is the gold standard but we've used aerosol brake cleaner w/ good results. Be careful as the filament is fragile.
Often times it is not the AMM but the connections at the plug by the AMM. The 5 or 6 pin connectors are dainty; they can corrode and/or get bent and pushed round to where poor connections are the result.
Be sure you wipe the codes out of the OBD. Often times, old codes inadvertently left in the system send us looking in the wrong direction. Wiping the code and havingthe same one return is a much better indicator that you're looking in the correct direction. Frankly, your symptoms sound more like a failing crank sensor or fuel pump relay. Still, a multi-meter and a manual would help a lot in isolating the issue.

 

thanks,, i will begin with your suggestions, one question, the crank sensor , where is it located? i looked in my haynes repair manuel and i can't find any referance to a crank sensor..

 

The crank sensor mounts to the back side of the engine where it meets the bell housing of the transmission. Right at the top of the bell housing. Fortunately, crank sensors have a rather long pig tail on 'em so you can access the connector rather easily. There is a cut out on the back of the bell housing that looks like this...

The crank sensor mounts to the rear of the engine and protrudes into the opening shown on the bell housing.