# 3 alts - engine idle problem



## tRidiot (Jun 29, 2006)

Ok, so today I hook up my 3 alternators (270A + 270A + 145A). Now my engine is idling very low, like 500RPM, and when I shift into drive, it drops to around 200 for 2-4 seconds before moving back to 500 or so. When I move forward (just into the garage, 5-10 feet), it dies when I stop. Dies when I restart 1-2 times, then repeats the whole thing. Charging voltage is 14.88, up to 14.96 when pressing the gas.

Quite annoying. Some have suggested the computer needs to readjust after several hours without power. Some say my 3 alts are pulling my 5.3L Vortec V-8 for 60HP, causing it to lag... I dunno. Seems a little far-fetched to me. Some increased drag, yes... but 60HP? With essentially no load? The system is unhooked at this point.

Currently only hooked up to the backup battery. Only ground right now is through the alternator bracket and direct battery hookup itself. The alts have no specific ground hookups (). I have a copper ground buss bar off an alternator bolt, but again, only the battery ground is hooked up to this. The alts are paralleled into the stock wiring harness.

I plan tomorrow on adding 1-2 more grounds to the engine block and/or chassis, plus throwing in the main battery. I have a custom-built triple-alt MLA module on the way... $279 sounded awful high initially, but if it fixes my problem 100%, it is totally worth it. Should be here tomorrow or the next day at the latest.

I have heard the computer has trouble controlling 3 alternators. If this is the problem, the MLA module should help, I think.

So I'm just venting... looking for opinions.


So... what's going to help the most?

1. More and better grounds.
2. Adjusting idle up.
3. Allowing time for computer to readjust itself.
4. MLA module.


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## ryomanx (Feb 18, 2011)

i would try adjusting the idle speed. i think adding the resistance of two extra turning pulleys maybe bringing the idling down. (no scientific evidence but a thought) Hmmm, is the computer suppose to self adjust for low idles? is the ECU throwing any codes? What is the YMM?


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## Hillbilly SQ (Jan 26, 2007)

If you have a weak battery it will also die immediately after starting. My 01 Silverado with the 4.8 in it was the same way. Bone stock it idled at 500 and starting it with the engine warm it would drop down to around 200, almost peter out, then go back up to 500. Never was erratic. I also think the drag from the extra pullies is causing issues along with your computer sensing something not being right. You could always take it to a GM mechanic. You'd likely get raped on price but beats possibly frying your computer.


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## tRidiot (Jun 29, 2006)

Battery is brand new and very strong. Gonna try a few things today and see where things go...


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## Streetbeat Customz (Mar 19, 2011)

This is happening without playing the stereo?


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## tRidiot (Jun 29, 2006)

Streetbeat Customz said:


> This is happening without playing the stereo?


Stereo is disconnected... well, except the headunit. No amps on, no music playing.


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## Streetbeat Customz (Mar 19, 2011)

Interesting.

I could see them taking 20-30hp from it when they all have a load on them. But without the load, the alts shouldn't drag it down that bad.

Can the rpm's be set higher?

Bypassing the internal regulators with the MLA maynot help as it will only see a higher V - not really affecting the rpm's.

Maybe hit up the company you got the alts from and see if they have had this problem before?


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## tRidiot (Jun 29, 2006)

Well, this morning the truck ran a ton better. I'm thinking it had something to do with the computer being off power for 6-8 hours and it just being hooked back up before testing the charging system. It ran much better this morning, minimal change in the idle, back up to where it was before.

My MLA alternator control module also came in and it is now wired and functioning. Charging voltage at idle is now 15.4V! W00T!

Overall very relieved and happy with the electrical system... now I have to fit in 3 huge amps, HLCDs under the dash and finish the electrical distribution center under the hood.

Oh, and make RCA to XLR cables for my Behringer unit and get that installed and programmed. Can't wait!


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## thehatedguy (May 4, 2007)

If you've disconnected power like that, the ECM would reset itself. And then it wuold have to relearn all of the fuel curves. What happened sounds normal for a reset ECM. It will get better as it relearns your fuel and ingition trims.

My car immediately after resetting the ECM runs really rough. Goes away after driving it a few minutes.


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## Streetbeat Customz (Mar 19, 2011)

Good to hear


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## GLN305 (Nov 2, 2007)

The ECU being disconnected had everything to do with it. When I would power cycle the ECU on my Dodge Dakota after mods, it would run weird or not even wanna start the first time. Man, must be nice having that much charging!!



tRidiot said:


> Well, this morning the truck ran a ton better. I'm thinking it had something to do with the computer being off power for 6-8 hours and it just being hooked back up before testing the charging system. It ran much better this morning, minimal change in the idle, back up to where it was before.
> 
> My MLA alternator control module also came in and it is now wired and functioning. Charging voltage at idle is now 15.4V! W00T!
> 
> ...


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## cubdenno (Nov 10, 2007)

ECU. Our Suburban would do the same thing when doing stereo work and leaving the battery disconnected. You can imagine the horror of leaving the state for work and receiving the call from the wife and have her yelling at me for screwing up the SUV.


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## tRidiot (Jun 29, 2006)

Turns out we forgot to hook up the MAF sensor. DOH! Now it runs like it always did.

Thanks for the tips, guys!

Got the new system in and it is gonna ROCK when I get it all tuned up.

6600 watts total, almost all stealth. Look for the build log sometime next week...


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## Hillbilly SQ (Jan 26, 2007)

Nice. Did it blow black smoke by any chance when it was being cranky to start? To this day I refuse to unhook the battery unless I need to change it when it dies. Actually jumped a lady with a Yukon several years ago and told her that was going to happen. Sure enough the 6.0 under the hood was an ass and I had to assure here it was the computer relearning the codes.


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## Eastman474 (Jan 8, 2010)

tRidiot said:


> Turns out we forgot to hook up the MAF sensor. DOH! Now it runs like it always did.
> 
> Thanks for the tips, guys!
> 
> ...


I did the exact same thing when i did mine then Hmm that'll do it lol  glad to see you got it figured out


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## truckramrod (Jul 11, 2011)

Buy some Throttle body cleaner and go at it with an old toothbrush. Just clean the bore of the TB, remove all carbon from the backside and edges of the throttle blade and if possible, disconnect the MAF and start the engine with the intake tubing of and slowly spray the cleaner in the TB and IAC bypass, then engine will stumble but it will help clean the IAC (if equipped).

It will have a more stable idle after the Ecm compensates for the higher flow. Just make sure the key is not in the ignition (electronic TB can make you lose a finger)

This is part of a Fuel Induction Service at a GM dealer, which is typically over $140.

I've had to do this after replacing batteries on high mileage vehicles.

Good luck and I'm jealous of your 3 alt setup!


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