Hi guys just signed up so sorry if this is in the wrong area to put this kind of question

my question to anyone!

just bought a 1998 mitsubishi GLi 5speed man 1.5L lancer. when i bought it, it came with a very small under sized battery that if i left my stereo going for over a hour the battery would go flat, so i decided to buy a ultra high performance Century battery.
now my question is this, when i put the new one in, started the car, the car would struggle to hold revs, revving around 500rpm which would almost stall straight away, then i reconnected my amps and it seems a little better but as i took it for a drive anyway id pull up at an intersection of traffic lights the revs would fall and it would stall.

was wondering due to disconnecting the battery the first time would have disrupted the ECU or sumthing or could it be sumthing else!

look forward to your reply's

the vehicle has to "re-learn" the idle position. it will take a couple driving cycles. this is normal, mine does it. anytime you disconnect the battery, it clears everything out. you're fine, just give it some time

i don't thinks it were disrupted your ECU. for 1988 1.5 lancer.