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alternator rebuilt now idle problems
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chevycountry70
Novice
Dec 6, 2007, 5:52 PM
Post #1 of 5
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alternator rebuilt now idle problems
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I just had my alternator rebuilt, drove car about 20 miles and let it idle for about 10mins waiting on my wife to get off work. We then drove to gas station and put in 3/4 tank of gas in. When I went to drive off car died and started right back up went 25 yards and car stalled again. Drove another 3 miles got to red light car stalled again and the hand on the tack was idling up and down, idle up to about a grand and half then drop below 1 grand and stalls out. The hand on voltage meter was moving up and down. when your driving no problems at all just went your at an idle got home shut car off and started it right back up and the tack went to 2 grand then dropped below 1 grand then idled out to 1 grand but then started idling up and down voltage meter jumping up and down please help. Thank you
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scruff_08
New User
Dec 6, 2007, 6:22 PM
Post #2 of 5
(1427 views)
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Re: alternator rebuilt now idle problems
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I had the same problem with my blazer, a mechanic told me to change the O2 sensor and that should help. But of course haven't got to it yet. That would be my guess at least depending on the car its a cheap and easy fix.
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DrElectrics
Enthusiast
Dec 6, 2007, 6:45 PM
Post #3 of 5
(1423 views)
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Re: alternator rebuilt now idle problems
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O2 sensor or crank angle sensor I am thinking without seeing it. The volts are jumping because yoru car is idling irratically. The fast the drive belt moves the more charge your ALT will give. Its just a coincidence I am thinking. ALT is fine. Check the other 2 out.
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DanD
Veteran
/ Moderator
Dec 7, 2007, 4:01 AM
Post #4 of 5
(1413 views)
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Re: alternator rebuilt now idle problems
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Sorry guys but how can we start condemning sensors when (and now I’m making an assumption) that this vehicle was running ok before the alternator was replaced/rebuilt?
I agree with the Doc that the gauges could be going up and down because the engine may actually be surging?
As for the O2 I don’t think so, if it has shorted or gone off line the PCM would have set a code and light. If the crank sensor has a problem the vehicle would likely not restart or again at the least set a code.
I would start back at the original problem and make sure that this alternator is functioning properly and that battery voltage was stable. Check that the battery will accept and hold a proper charge.
If the battery had gone dead because of the original alternator or disconnected during the replacement of; the PCM may have lost all of its adaptive learning?
Now if this vehicle has some minor issues that the PCM were compensating for, it has lost that memory because the battery was disconnected. Something as simple as dirty throttle plates could be at fault. The PCM’s base adaptive setting (for lack of a better word) relies on a certain amount of air entering the engine, around the throttle plates. As the plates slowly become dirty the PCM learns how to compensate for this dirt and stores this info in memory. With the memory being partially wiped out it has too relearn this; drive the vehicle at varied speeds above and below 40 miles an hour for at least 5 or more mile, after the engine has reached normal operating temp. You could help this process by cleaning the throttle plate and idle control motor.
Like I said above I’m also making quite a few assumptions here but this is where I would start looking for this problem.
We have nowhere enough information, so guessing is all we can do?
Come to think of it we don’t even know YEAR, MAKE, MODEL, ENGINE! LOL
Dan.
Canadian "EH"
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chevycountry70
Novice
Dec 7, 2007, 5:29 PM
Post #5 of 5
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Re: alternator rebuilt now idle problems
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The car is a '93 Chevy Lumina Euro has 81,000 miles on it. I believe DanD was on the right track. I drove the car got it up to normal operating temp. then disconnected the ground cable, shut ignition off, let it sit for a few mins. Car is running normal for now. lol I'm guessing it had to reprogram its self. I can't thank you all enough, nice to know there are good folks out there that will help others. Wish you all the best. chevycountry70
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