Low fast idle on cold start causing charging problem

[Normand]

Hi to all,

When cold starting my wife's Wave 2005, 1.6L, automatic, Ecotech II, 46000km (29000mi), the battery light stays on in dash panel. After a little kick on gas pedal (more than 1600 RPM), light goes off. Restarting the engine and battery light doesn't stay on... Was like this every days.

I began changing my serpentine belt because so many cracks were on it and I suspected alternator was not running at normal speed. Was OK for 10 days and then problem came back.

Then, I noticed on the first start when cold, motor never revs higher than 1400-1500 RPM before falling to idle speed half-a-second later at 1100 RPM. I put a voltmeter on the battery and noted 12.4V. After very light kick on gas pedal... 14.6V. So, alternator malfunction...???

I disconnected the alternator cable from the battery post and tested it thoroughly. I put the meter on the alternator connexion and I can reproduce the problem. After starting, when the alternator is not connected: 1.9V. Then I connect the alternator on the battery: 12.4V. After going higher than 1600 RPM : 14.6V. Always like that, cold or hot start... I think it's the normal functionning with the electronic regulator inside the alternator. It needs a revolution higher than 1600 (a certain amount in alternator revs) to switch the regulator.

I conclude the problem is with the level of the fast idle at cold start...1450 RPM... After the first start, fast idle always reach about 1700 to 1900 RPM and the charging circuit is OK.*

What's the normal fast idle speed at cold start?
How could I put it back to normal?
Have you seen a problem like this before?

Thanks,
Normand
French Canadian

[wuwei37405]

That's a lot of information. Can you summarize your problem in one short sentence?

[Normand]

That's a lot of information. Can you summarize your problem in one short sentence?

Peak of fast idle at cold start is too low (~1450 RPM), giving problem with alternator's regulator circuit not switching ON and battery light panel stays ON after start. Brief depress of gas pedal to bring RPM's higher than 1600 switches regulator ON and battery light shuts OFF...

Normand

[wuwei37405]

Thanks. I understand the problem. It may take you a while to find a solution, but the first place that I would look is at the battery. Make sure that the battery cables connections are clean and tight.

[Normand]

Thanks. I understand the problem. It may take you a while to find a solution, but the first place that I would look is at the battery. Make sure that the battery cables connections are clean and tight.

All cables connections are clean and the charging system is working perfectly after I increase RPMs to engage electronic regulator in alternator...
The problem is: low RPMs at cold start (peak at 1450 then 1100) ...causing regulator to stay OFF untill I increase RPMs over 1600 for fraction of second.
Kind of air/gas mixture adjustment or injectors opening time problem at cold start... but don't know where to begin with that.

Normand

[wuwei37405]

I coud be wrong but it sounds like you have a problem with your charging system and not your idle speed. Check the alternator belt to make sure that it is tight enough. After that, you will need a meter and/or a technician to check the various components of your charging system.

[wuwei37405]

If I understand you correctly, you say that your car starts at 1450 rpm and then settles at 1100 rpm. That sounds normal to me. Anyone have a second opinion?

[Normand]

I coud be wrong but it sounds like you have a problem with your charging system and not your idle speed. Check the alternator belt to make sure that it is tight enough. After that, you will need a meter and/or a technician to check the various components of your charging system.

wuwei,
For the third post, I tell you I don't have a problem with the charging system, I already changed the belt and I did put a VOLTMETER on the system to do lot of tests...The system charges, but need a higher level of RPM to start charging.

[Normand]

If I understand you correctly, you say that your car starts at 1450 rpm and then settles at 1100 rpm. That sounds normal to me. Anyone have a second opinion?

Start at 1450 and settles at 1100 only at cold start. Next and following starts ~1800 and settles at 1100 without the no charging problem. I understand that I wrote "charging problem",but again, I think the problem is a lack of RPMs at cold start. It looks like the regulator (the electronic circuit inside the alternator who rectifies and regulates the voltage from alternator) needs a certain level of RPM to trigger and switch to ON.
Maybe the problem is with the regulator by itself.... but I replicate this problem by disconnecting the alternator cable from the battery and connecting after the start (then at 1100 RPM) and every time I have the problem of the charging system need a little kick on gas pedal (RPM going over 1600) to engage (electronically) the regulator...
Could anyone take a look at their RPM at cold start and post the exact peak in the first second. That will tell me if my regulator is normal or if the problem is with the fast idle peak at cold start.
Aveo 2005 Ecotech II 1.6L

[wuwei37405]

I appreciate your frustration with having to repeat your message three times. I apologize for not listening. Still, based on my 2005 Aveo LS, your RPM's are not low. Is there anyone out there with a different opinion?