a spot of flatness

[alpinaclone]

The old m20, between approx. 4000 and 5500 rpm has a huge flat spot. It feels as though it looses about 30hp in that range. It really falls on is face, it builds rpms more slowly, the intake and exhaust note flatten and it just feels like a slug. The key here, I think is that when it hits 5500rpm it comes back on full song and pulls 'till redline. This is leading me to believe, after many hours of not doing any research, that I have a bad spot on the pickup in the airflow meter. Does this sound plausible? The car is in a good state of tune and is essentially stock. Any help is appreciated.

Also, I haven't searched this and I prolly should, if, in fact the flapper door is bad, is there any kid of ghetto fabulous $0 way to upgrade to an airflow meter?

[jlevie]

The AFM would be a reasonable suspect for those symptoms.

[alpinaclone]

All of the clues point in that direction, at least in my head. Is the offending pickup under the black plastic cover on top of the flapper door? I am going to dig out the old multimeter and do a sweep of the door and see if there is continuity across it's whole range of motion. Does that sound reasonable? Does anyone have any other tests that one could perform with limited tools? Thanks.

[jlevie]

See: http://frwilk.com/944dme/afm.htm

[alpinaclone]

Super helpful, thanks man.

[alpinaclone]

jlevie, thanks again for that link. I moved the position of the pickup as described on that site and it took care of the problem. It was so simple, I'm ashamed that I didn't think of it myself.