Got a Prlelude Si 2.0 Dohc '89. Never gives me any problems, From time to time when roommate drives the car after is has gone all day in the evening it won't start unless you unplug the battery for half an hour. Won's spit a trouble code to me, and as i said won't play that mess when i'm driving. Does this have to do with her driving like grandma and myself driving as if everyday is a race? or what?

 

What happens when it will not start? Just cranks or not even that? Sounds like an alternator charge problem..

 

Yep cranks strong, battery has plenty of juice. I noticed by the L.E.D. on the ECM that when this is happening the ECM doesn't boot. Wondering if anyone else has had similar problem and if there is any other explanation than the $800+ ECM unit....

 

$800???? jesus. ill sell you one for $400...

you disconnecting the battery is actually reseting the ecu. all you need it disconnected for is 30 seconds.

 

well, so far i know that when it won't start it is due to no fire at the coil pack and no pulse at the injector plugs, and this is when the ECM doesn't boot(duh i guess...) but what's odd is normally as you'd need to disconnect the power for about 30 seconds or even a minute to be safe, sometimes all i have to do is turn the ignition back a sec and try again, other times i can leave the battery unpluged for hours and it still will not start, even more odd today for the first time the ECM went into "limp home" mode and before it always ran fine(when it ran). i also notice while the battery is disconnected there is a small current draw every few seconds(judged by circut tester between hot post and cable) and it varies in amperage and duration. this is with all doors closed and ignition completely off, CD face off nothing should be able to draw... did you say you had an ECM for a B20A2?

 

Well, i'm certain it's either the ECM or a short somewhere because when the ECM is functioning, there are no trouble codes, all sensors read fine, diagnostics say everything is tip top... the engine cranks in 3 turns EVERY time, unless the ECM doesn't boot, and what's more the more i play with it the less it will act up, the more someone else plays with it the more it wont run.... karma anyone???