Hi,
l have a honda civic 1991 dxautomatic, when l start the car it starts right away and then it turns off about a minute or so later on its own accord, l was told by someone it might be the main relay, where is it located and could send me a diagram orpicture of the main realy

the problem is not the main relay. the main relay was a problem on the 90-93 accords but not on the civic. the main relay would prevent the car from starting as it usually stopped the fuel pump from working.

does the car start back up after it shuts off after the minute or so? what happens after that?

you may have a low base idle; the first minute or so you're in 'cold start enrichment' if the car comes off the high cold idle & ur base idle is low it would cause it to stall.

if the car does not start back up after 1 minute then look for a clogged fuel filter or a vacuum leak. when the cold start enrichment stops after a minute or so it turns off the excess fuel. any vacuum leak could cause the engine to stall from too much air & not enough fuel once the supplemental cold start fuel is cut out.

that is the best l can offer with the info u provided.

hope it helps