View Full Version : Sr20det loses voltage at idle causing lean

09-25-2019, 10:25 AM
After my sr warms up basically everything happens at once the idle drops to about 300 to 400 my voltage drops to low 12 volts and car leans out. Timings good, new alternator, wired small wire on alt plug to light to 12v, fuel pressure stay 40 psi, new fuel pump, checked tps voltage, cleaned iacv. I'm stuck at this point when driving it drives fine the ecu code is knock sensor which I have on the way cause it's all cracked. I have to put my foot on the gas when I come to a stop so it doesn't lean out and or just die out.

09-25-2019, 06:18 PM
Voltage will drop cause the idle drops. Alternator is spinning as fast to create proper voltage.

Check if your tps/timing is set properly.
Check for vacuum leaks
Check idle air control valve operation
Atmosphere bov wont help either

09-25-2019, 11:01 PM
Try a new alternator. As they start to fail they can loose power after heating up.

Have a great day,

09-26-2019, 10:41 AM
Try a new alternator. As they start to fail they can loose power after heating up.

Have a great day,
Did u read the post?

09-28-2019, 09:55 PM
1. new alt can be bad
2. voltage is control by alt so if voltage drop then alt isn't working

3. if alt is good the only way you can have voltage problems is if
one or more of the key wire groups (ground strap from engine, ground wiring lug by kick panel, ground strap on intake, ground strap on exhaust, ground strap for coils, ground strap for chassis, and main power feed/fuses)
is missing or bad, or one of the key wiring elements (ECU plug/sensors) is loose or bad,

or if the alt is undersized for the application.

09-29-2019, 07:18 AM
Again, hes checking voltage as the engine stumbles.

Have someone hold the rps at 2000. Then check voltage. Post what you got.

09-29-2019, 08:07 AM
When you say new alt, is it used, new oem, or new reman?

If voltage is dropping, that's almost 100% indicative of an alt. Easy button is to just take it off and take it to your local auto parts and have it tested. It's not uncommon for even new reman alt do not work. Also, did your properly tension the belt? Belt may very well be slipping

Also, check your wiring to make sure.

10-01-2019, 10:33 AM
and don't underdrive the alternator lol, but also to thin of wiring creates to much resistance, I have been through 4 alternators this year due to same issue...low voltage or voltage regulators going out...my fault for sticking with same brand but free replacements are hard to say no to lol, check relays and fuses...a main fuse blown can cause similar issues...a new alternator doesn't mean a good alternator...check volts and make sure amperage is correct too

10-04-2019, 03:29 PM
I've never had an OEM alternator failure on any sr20det nor have I even heard of it before this.

Alt should be the easiest part of the entire car, its like 2 wires and it spins. Try an OEM alternator with 222,000 miles and get on with life?