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Discussion Starter #1
My car is at the tuner getting some #80 injectors swapped in. I talked to the tuner last night and he said everything is gravy except that if he sets the idle to 850rpm that it'll be rock solid until the fan comes on(Dual Ramchargers fan controlled by the AEM itself) that the idle wants to drop to 300rpm and will not respond to any changes.

Anyone have any idea why this is happening? I really want to get this controlled, even if I have to buy a DCC fan controller to get it straightened out. I don't like the big "surge" that happens with the AEM controlling the fan anyways but I guess that fan on high some serious draw and causes it.

Thanks guys.
 

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If you are running under drive pullies the alternator is probably
not putting out enough amps at idle and you are getting a voltage
drop that is freaking everything out.

or you could have a bad/loose ground or need more grounds.

or battery could be getting weak.



anyway ........ voltage drop or ground issue is where I would start.
 

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Discussion Starter #3
Thanks.

The car does have a PA Performance 3G alt on it with a stock crank pulley so it SHOULD be ok. I will check the car when I go over tomorrow and see what the voltage is.

Probably grounding issue then, these cars didn't have enough as it is.

It SHOULD be able to work with the AEM controlling the fan if everything checks out correct? Is there anyway to wire the fan up so it doesn't have that "spike" when it comes on or is that the nature of the beast when you have a fan that pulls a big current and basically an "on/off" trigger to turn the fan on? It's wired up with the AEM grounding a relay to turn it on btw.

Thanks r.barn, you help me out a lot..haha.
 

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sounds wired up right.
AEM will control fan fine. something is going on for sure.


check out a comparison data log I did in the AEM before and after
adding a bunch of fine strand ground cables from the
battery, frame, engine block, firewall and wire harness.


both are at same scale.
Lines are for things like voltage, MAP sensor volts, TPS, ect.

Before



After
 

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When the fans come on, does the car go lean or rich? How much current are the fans pulling?

Can you post a log of what happends when the fan come on. Logging. Batt Voltage, engine speed, engine load, idle learned %, #1 o2.

Lawrence
 

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I don't know if you're still fighting this or not. It wouldn't be a real cure for the problem, but you could lessen the startup load by using 2 different ECU outputs for the 2 different fans, and staggering their startup.

I have a DCController but even its soft start puts a good load and rpm drop on the engine. I'm hoping I eventually get the tune so it can handle the extra load, but if not, I'm going to try to use the "Idle Extra <12 volt" table. I can't run AEMPro here at work to confirm what I'm saying, so I'm pasting in the help file for it. I think the voltage is adjustable... its not actually fixed at 12.0 Volts. Anyway, I was thinking of setting it at like 13 Volts and seeing what happens. Here's the help file text:

Idle Extra <12 Volt

Units: Idle %

Description: The amount of additional idle duty to add when the battery voltage is less than 12 volts. The number can be positive or negative depending on how the idle motor responds. Helps in charging the battery and keeping the vehicle from stalling.


EDIT: I am wrong. The idle extra is fixed at 12 volts.... it's the percentage of rpm increase that is settable, not the voltage. Sorry about that.
 

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Discussion Starter #8
Guys it's time to get the car back out so I have to fix this. I emailed DCC about their controller but would rather make what I have work instead of buying something else. I was thinking about making the fans turn on low instead of high. Is there a way to lessen th initial load with dual relays or something? I want to add more grounds also, anyone have a good how-to or article? I want to do it without cluttering engine bay. Thanks
 

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I had a similar symptom recently on a car I was tuning. Once a high load devise was turned on, the car would go lean and want to die. I got it to not fluctuate, but I had to make a very large adjustment in the battery offset table. By the way the car was acting, I knew there was a voltage problem. While the AEM ems showed battery voltage fluctuation was less than half a volt, there had to be something going on. I did a voltage drop across the injectors when the load was turned on. Bingo, 2 volt drop. Problem ended up being a ground problem as the car did not have proper grounds in the correct locations.

Check for a voltage drop on the power and ground and you may find your issue.
 

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Yep, battery offset table. Try changing the wizard first. Also speed the IAC motor up a little Change it from 300 to 100-200.
 

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Yep, battery offset table. Try changing the wizard first. Also speed the IAC motor up a little Change it from 300 to 100-200.
X2

The DCC conroller is one of the best parts you can buy for your car, trust me!!!!
 

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I know this is an old thread, but it's relevant. To prevent the huge current draw, should the AEM send its signal to a controller (DCC, Derale etc.) instead of just a relay?
 
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