So called second conjugation verbs of SMG–verbs accented on the ultima of the first person singular–were shaped by the addition of ε to α in AG forms such as τιμά > τιμάει
Verbs that are end stressed historically were denominal verbs. The form τιμάω contracted to τιμώ, τιμάει to τιμά with an iota subscript.
In accordance with Watkins Law, according to which 3rd person forms are the pivot upon which paradigms are reconstituted, analogically to first conjugation πλένει or κάνει an -ει was added to mark the third person as τιμάει yielding the first person τιμάω.
The form οδηγάει appears but not παρακαλάει, μποράω etc. –it’s the kind of change that happens on a word by word basis (not a sound change but a morphological change through analogy–while sound changes happen everywhere, morphological change is sporadic.)
See articles by Janse and Joseph and Householder and Nagy On Modern Greek:
- Watkins’ Law and the Modern Greek Preterite. Die Sprache 26.179-184 (1980). (PDF version)
In this paper, I talk about Watkins’ Law in Greek and refer to Householder and Nagy 1972 regarding forms like τιμάει as being from τιμά (as the continuation of AGrk τιμᾷ), analyzed as a *stem* τιμα– with a zero-ending (thus τιμα-ø) and then with the productive 3sg ending –ει added on to mark it overtly as 3sg; so also then with 1sg, coming to marked overtly as 1sg with -o (orthographic < ω >) added on to what was now taken to be the stem (thus: τιμα–ω)