I've had a bad idle problem lately. Codes indicated ect fault. I bought one from fcgroton and replaced. Also replaced ox sensor will one for 92 mustang v8, per faq and responses on board. Seems worse, will stall out more often.

Symtoms: No high cold idle. After warm-up car will "miss" at idle, sometimes die. Weird smell from exhaust. Lots of moisture in exhaust, after sitting two days. Will run fine at speed. RPM's as indicated on tach, will sometimes peg, and jump around very erractically when trying to start. RPM sensor was replaced about 4 months ago, I pulled and cleaned it to check.

Codes are: 123-ect which I've replaced.

221-lean/rich mixture replaced ox sensor

121-signal from amm bad. Don't want to replace unless I have to! I have removed the plug from amm and car does run different, will miss at speed, and stumble at idle.

Can the amm be half bad?

Wouldn't the fault be across the board and car run in the limp-home mode without disconnecting the plug?

Any ideas on problems?
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1985 740gle na, 1990 740gle 16 valve