I just finished doing a longblock swap on my car about a week ago. Actually took it to a shop to get it running. Car is a 99 Civic Si, now has a 1st gen JDM B16, converted to OBDII.

Few days ago I started getting rough idle and would turn off if driving in traffic. So I restart it and it's fine. But today, it turns off while I'm at a light, I try to restart and the ****** dosen't! Starter is making a clicking noise.

So I tow it home. Replaced the battery with one from my friends, car starts right up. So we put mine back in, no start, same clicking noise from starter. So we jump it, starts right up. After 5 minutes we detach the jumper cables and the car runs fine for about 2-3 mins. After that, the idle starts to get rough and the car dies by itself!

I'm thinking bad alternator. It's not charging the battery at all. What do you guys think?

I'm thinking to get the battery recharged so I can drive it to a Napa or Kragen to get my alternator/electrical sys checked out.... I will check my connections to the alternator in the morning.

Oh yea when the idle started going rough I got a CEL, code 3 (map sensor). It didn't have a CEL when I got it first running, only when the idle became rough, which was a few days after. I think it's related to the battery/alternator issue but the ECU thinks it's the map sensor for whatever reason... Map sensor harness is plugged in and the O-ring is in there. Hmmm...


[Modified by THE PLAYER, 9:13 AM 2/1/2003]

 

Definitely sounds like the alternator, replace it as soon as possible. If you want to be sure before you replace it, just throw a voltmeter on the positive side and see what the voltage looks like after a fresh battery charge and starting the vehicle. If you see voltage drop over time, and when revving to a minimum of 2000 RPM it doesn't pick up to near 14 volts, it's definitely the alt.

 

i'll go ahead and do that. Hopefully I can get my hands on a voltmeter.

Oh yea, I put a brand new battery in there when I was doing the swap. So if the alternator is bad, that means I used up all the battery juice in a week driving around and ****. I still gotta check my alternator connections, maybe somethin is just loose.

Anyone else with any more ideas, please drop a line

 

well I looked around and I noticed the bottom alternator bolt is not even torqued down on the bracket

I did a search and found a post where this guy powder coated his alternator brackets which caused the alternator to not get a ground, therefore it wouldn't charge. He went ahead and ran a ground from the bracket to an engine mount and that solved his problems. I have to run out tomorrow and find that 10mm nut so I can torque that bolt down. Hmm that might be the problem lol.

Oh yea also did a test today. Swapped in a brand new battery, car started right up. I pulled the negative off the battery and it just died. So I know it's either the alternator or connections to the alternator.... I'll keep you guys updated

 

Take your car down to autozone and get them to load test your alternator. That's the sure fire way to know.

 

Kragen said my battery is holding charge, starter is fine, but the alternator is only giving out 11.85 volts. I searched here and found that if it's not giving out 12V, it's not going to charge the battery. Hmm looks like I have to get that flange nut from Honda so I can torque that alternator bolt down. Will see what happens after that...

Anyone w/ other ideas?

 

*update*

well I looked at my grounds and I noticed the valve cover ground was bolted on a different location. hmm so I put it where I thought it was supposed to be. disconnected the neg from the battery and the car kept running prob solved!

all that thinkin and all it was is a ground wire moved 1 inch to the left

it's all good now. just thought i'd update it if anyone cares