beebone

Seems I read relevant post long time ago, but i forgot what casue this problem.
Last post I've mentioned, the AFR can't adjust up to 14.7 by the AFM bypass screw, stand still at 13.2.

I got an answer today why can't be 14.7, when I pump the brake at idle, the AFR goes close to 14.7 from 13.2, then fall to 13.2 when stop pumping the brake. Any ideas? Thx!

400hp944

Bad alternator, battery or a grounding issue. Does it change when you turn the lights on?

beebone

No change when I turn no head light.

Sounds logical, I saw the volt meter from 13V something (cold start), then drop close to 12V when warm. I feel like the battery or may be alternator got some problem.

400hp944

Check and clean the grounds at the rear of the car. Pull the carpet back to expose the the area where the hatch latches are. There are a couple of grounds there next to the built sticker. Pull them off and clean. Next I would replace the ground wire from the battery to the engine - even if it looks OK.

Van

Current draw - either because the engine speed dips due to the extra load on the alternator, or because of bad grounds.

beebone

Yes, my battery is installed at the trunk on the left side. Ok, let me clean the ground terminal first, see hows it goes. thx!

Chris White

One other possibility (not likely – but possible) – leaky brake booster.

Try adding a different electrical load (head lights) to see if it does the same thing. If not you may have a vacuum issue instead of an electrical issue.