2001 Honda Prelude Electricaly induced idle problem

  • 4 CYL
  • FWD
  • 99,000 MILES
About 18 months ago I replaced my alternator, it went bad and had a weird symptom of making the brake light come on. About 2 months after that I took the car off the road because it was time to replace the timing belt and water pump. That was December '08 my original plan was to replace the belts when spring hit, but we had a new baby on the way and that kind of changed my priorities. In late October 09 I finally got in and replaced the timing belt and water pump. I changed the plugs and wires too. When I finished everything up I had some issues. The first thing I noticed was that it idled erratically, so I checked the timing. It was all set right.

So, after it warms up the idle drops to normal idle then surges. It surges between 900 and 1300, while it's doing that the dash lights dim and brighten and the battery light comes on. If I turn the key off and back on it stops. It seems to run fine when it's not at idle, but the battery light comes on. After I kill the ignition and turn it back on it idles fine until I rev it up to above 3000. The headlights dont work in low-beam, only high-beam. I also took the alternator to my local shop and had them test it, they said it was fine.

I used the Helms manual to troubleshoot the charging system but got stuck when I went to check the connection to the ECM (or ECU). I cant find the damn connector to check it. Where is it? I'm looking under the dash but cant find it, a picture would be nice.

Any thoughts as to what this could be?
Do you
have the same problem?
Saturday, February 20th, 2010 AT 4:45 PM

1 Reply

Hi cuzimbob,

The ECM is at underside of passenger footrest.


Is the CEL showing?
Was this
Saturday, February 27th, 2010 AT 9:08 PM

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