why does engine stumble at idle under electrical load?

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Old Jul 25, 2009 | 10:40 AM
  #1  
Dan3952's Avatar
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From: Fort Saskatchewan, Alberta
why does engine stumble at idle under electrical load?

Got a problem... at stoplights when the two fans kick in the engine goes below idle speed and stumbles momentarily. To a lesser degree the power windows do the same thing. Cars I've rented recently don't do this. My first thought was the old alternator can't put out enough juice, $280 later put a new one in, now it's still doing it but to a slightly lesser degree. What could be causing this? Canadian Tire wouldn't test the 2 1/2 year old battery although it's under warranty, they said it's the engine because I probably have a bearing that's wearing out. If the fan motor bearings are almost gone they can stay that way.. the fans are a dealer part and $230 each. If I get a new battery I have a feeling it won't solve anything, it's never failed to start the car
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Old Aug 9, 2009 | 06:16 PM
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whiteyy97CL's Avatar
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From: Poulsbo, Washington
ya my cl does this too. i work at a car dealership/service department and a lot of the older cars that come in will have this problem. i'm not a tech just a detailer so i'm not sure what it is. lol just sayin you're not the only one.
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Old Aug 20, 2009 | 11:10 PM
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by electrical load..do you mean just the fans themselves..or do you have more things set up..if so..a regular battery will drain much faster over time even if the alternator is good..it can't handle so much drain time and time again..you're basically straining out 2 major electrical parts at the same time..so if u have a system..or sumthing of the sort..get a capacitor ..or an optima..
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Old Aug 21, 2009 | 10:13 AM
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or both
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Old Jan 26, 2010 | 01:55 AM
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you say Optima battery my question is if they fit under the hood without any mod. i only reason i ask is that i read this .."OE battery has flush vents, remove or modify heat shield. Require bottom height adapter, check hood clearance." this was while i was looking for one from autozone.
1997 cl 2.2

thanks for your help
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Old Jan 26, 2010 | 07:34 AM
  #6  
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Originally Posted by 97BlackAckCL
or both
Or neither... Get an XS Power batt, it's well worth the money, and a D5100R can be had for about the same price as an Optima G34/78. I ran the car and 1500w on the stock alt with the 1 D5100R with very minimal voltage drop, something that a capacitor nor an Optima can do. A cap is designed to discharge it's stored current very quickly, and will then draw from your alternator to recharge itself. This causes more strain on your alt than without the cap. And while the factory accessories are not drawing current for very long, they will still need it for longer than anything smaller than say 5 farads will be able to output. An Optima is not designed for quick discharges, like car audio batts (XS Power, Stinger/Ody, etc). Therefore, they won't for sure fix the problem you're having. With my 5100R, my voltage would drop .2 or so when rolling up/down the windows or when the fans kicked on. That is better than any Optima or cap, and using a batt of smaller size. Now that I have installed my D2400, I have 0 voltage drop when I turn on the heat. I haven't tested the AC or windows yet since it's been too cold, but again, that's about a .1-.2v improvement over the D5100R.

As to the question at hand, the reason it's stressing is that factory electronics require more voltage (rather than current) to work correctly. I had similar problems with my car, even when not pushing the system. Then I switched to the XS Power batts, and haven't had any problems since. So if you're going to replace the batt with something, definitely look into XS Power. I got my D5100R for $160 shipped, IIRC, which is about the price (if not less) than a G34/78 Optima Yellow Top.

This is just my personal experience, but I figured I'd share it with you guys so you don't go and waste lots of money on a cap that ends up hurting more than helping. A well designed batt does the same thing, but better. They will have similar discharge rates, but the reserve capacity is much much higher, which is what is needed.
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Old Jan 26, 2010 | 10:02 AM
  #7  
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Another thing I just thought of that will help is called the Big 3. You replace the stock wires from your alt output (+) to your + battery, and your 2 battery grounds with larger wire. I used 1/0 awg and Chris used 4awg to do this. The larger (but still good quality) wire you use, the better your results will be.
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Old Jan 26, 2010 | 11:33 AM
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Mine does that too and I don't have a sound system or anything other than stock electrical devices.
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Old Apr 12, 2010 | 10:42 PM
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From: Pittsburgh, PA
I have the same problem with my 97 2.2L. It jitters whenever the lights come on, or the fans, or the wipers. I was afraid of a weak alternator in it, but I hooked up my 1000w Memphis and my 12's, and it keeps up just fine. I wouldn't worry about it.
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Old Apr 12, 2010 | 10:48 PM
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i think its quite normal for our old cars. don't forget they are 10+ years old now...

As long as the rpm doesn't drop dramatically, it should be fine. If it really bother you, clean out the Idle air control valve passage. It'll do a better job at controlling the idle and regain the dropped rpm when the alternator is stressed whenever the fan kick in (especially when the A/C fan is working too, in conjunction with the A/C compressor)
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Old Apr 17, 2010 | 02:05 AM
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I had a similar problem with my 2.2CL. I had my a/t replaced and things didn't seem to work the same. Mostly electrical. while driving I noticed my temp gauge spike up and I immediatly pulled over. Knowing a little bit about cars, I noticed the engine compartment wasn't that hot to be overheating so I started feeling around to see if anything came loose. I found both battery cables and all engine grounds and my transmission ground to be loose. Sorry bastards couldn't even tighten those up. I thankfully had a couple tools in my trunk that allowed me to tighten up everything. Still went back to the shop to have them double check everything. "for free"
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Old Apr 17, 2010 | 02:08 AM
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TexasTony6777's Avatar
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All in all though this could be a result in older wiring. Have someone check for shorts, amp ratings and draws throughout the car. sometimes it's just a simple short or too much restriction in a harness that might be corroded.
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