Need help with running issue/OBD codes

[mech4matsnova]

I was coming home from work yesterday and my car did something its never done before. I did my normal thing, let it warm up for a few minutes and just drive easy, no hard driving on my way home. When I left work, the speedo wasnt working and my radar detector didnt come on so I figured I had a blown fuse somewhere. About halfway back, I went to downshift to make a turn and the car backfired and stalled and the MIL light came on. It fired right back up and ran fine the rest of the way home. I didnt downshift anymore so I wouldnt stall again. I got home and put my code reader on it and it gave me two codes, P0100 mass air circuit a and P0500 speed sensor fault. I put dielectric grease on the mass air connector and made sure nothing got in between the cold air and the intake manifold. I also checked the fuses in the fuse box and everything looks good. As far as the speed sensor, I thought I might have a pinched wire near the shifter because thats where my speed cal is located. Ive spent two hours looking at everything I can think of and both are doing the same thing. Im not a mechanic but Im mechanically inclined. Any suggestions? Thanks ahead of time for the help.

 

[Lee12609]

test alternator output...

 

[mech4matsnova]

I hate to drag this back up, but I took the alternator off and had it tested. Only put out 11v. I got a new alternator and put it in. Car still runs ok, but still stalls on downshift and still dont have a speedometer. I checked everything that hooks to my speedcal and it is all ok. No blown fuses. I checked everything hooked to the maf, didnt find anything wrong. Help please... :dontknow:

 

[AaRoN]

Have you reset the codes since?

 

[last5.0steve]

Take the speed sensor out of the trany and check the driven gear on the sensor and look inside the trany speed sensor hole with a mirror to check the drive gear to make sure there not worn or missing teeth. that code you got for the speed sensor is created when the computer does not see a speed input. Foe your mass air code you may have a bad mass air. the software in the pcm for 98 mustang wasnt very technical for mass air codes usually if you get a mass air code at all the problem is the mass air.

 

[mech4matsnova]

I got it. I cleared the codes, it was stalling because of the pcv hose to the inlet elbow was cracked bad and sucking in air. I replaced that. The speed cal wasnt getting power so I used the unused convertible top harness power to run to the speedcal power and that fixed it. Cig lighters dont work now but all the fuses are good. Dont have power to either outlet. Any suggestions?