Car is tuned, runs great, at idle it dies when all the electronics are on

Makoto

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So yesterday she was tuned and I got her home today. I had an issue with the fan wiring which i fixed but now when that sucker kicks on at idle the engine stalls out.

Everything is new. Battery, alt, maf, iat, coils, no vacuum leaks, and the voltage is good. I noticed it when it was idling and i was shutting down. I went to roll up both windows at the same time while the low spd fan was on and it just kinda puttered out.

For those that don't know when you draw current from something like an alternator it causes resistance which puts load on an engine. we've got 60 amp fuses in these coolant fan circuits, the draw a lot, so i don't think I'm being out of line when I wonder if the IAC needs to be adjusted with the fan plugged in at idle.

I've never had a car tuned like this. Is it customary to just call the guy, I bring it to him, and he adjusts whatever he needs to?
 
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ttocs

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The tuner doesn't really do anything about the voltage/power. It sounds like your alt is struggling to produce the voltage/current needed. I would start simple by checking all the connections on power/ground and by check I mean remove, clean, retighten.
 

Makoto

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The tuner doesn't really do anything about the voltage/power. It sounds like your alt is struggling to produce the voltage/current needed. I would start simple by checking all the connections on power/ground and by check I mean remove, clean, retighten.

everything is new and it was fine before the tune. its not that. IAC needs a bump, it idles lower than what it used to.
 

ttocs

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everything is new and it was fine before the tune. its not that.
just because it was new and fine before does not mean that it is not now. It could also be the battery going bad and dragging the system down. So far I am just naming some basic stuff that the tuner does not cover that he could fix for you but you will probably pay an hourly rate to do it.
 

Makoto

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just because it was new and fine before does not mean that it is not now. It could also be the battery going bad and dragging the system down. So far I am just naming some basic stuff that the tuner does not cover that he could fix for you but you will probably pay an hourly rate to do it.

look, i know you're trying to help and stuff but here are the facts:

1. the car could idle forever with the high speed fan on before the tune
2. the car can't even idle for more than few seconds now with the low speed fan on after the tune

this isn't rocket surgery.

i appreciate the attempt but if you're going to second guess what i said in my post you might wanna move along to the next thread.
 

ttocs

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your absolutely right it is not rocket surgery. Electronics goes bad all the time and if you do not start by checking the simple stuff you end up chasing your tail and cursing really loudly when you finally do check them. I am serious when I say it could just be a bad connection to ground or a battery going out but if you don't want to consider them then I wish you the best luck.
 

96blak54

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Can the fan output skew with maf sensor readings? If the air intake is shared with engine bay, the fans output can skew with maf readings.
 

muzzy25

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Can the fan output skew with maf sensor readings? If the air intake is shared with engine bay, the fans output can skew with maf readings.
I think iac Tps maf are ecu 5v
Fan ecu fuel pump relays are in a housing
I would raise idle speed to were it was before?
 

lwarrior1016

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IAC is a 12v circuit. If it idled the day you took it to the tuner, and it won’t idle now, give the tuner a call and see if he can do a touch up. I’m sure he would take care of it.
 

ttocs

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I thought the IAC was a PWM system myself after trying like hell to find the right freq and then going to a GM style for my holley, but I think we have now covered any system it could be now. Its possible the fan is creating some EMF that is causing some problems but then the with the windows tied in I am not so sure.

Does it stay at 12v when the fan/windows are going or is it getting down to a critical voltage that is shutting it off? You would be better off testing this with a meter hooked up to see the voltage number rather than relying on the stock gauge.
 

Makoto

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I thought the IAC was a PWM system myself after trying like hell to find the right freq and then going to a GM style for my holley, but I think we have now covered any system it could be now. Its possible the fan is creating some EMF that is causing some problems but then the with the windows tied in I am not so sure.

Does it stay at 12v when the fan/windows are going or is it getting down to a critical voltage that is shutting it off? You would be better off testing this with a meter hooked up to see the voltage number rather than relying on the stock gauge.

I'm going to do some more testing today because I was thinking maybe my battery relocation situation could be the issue. The setup shows zero voltage loss so I think we're good but the battery might not be up to snuff.

Here's what i got so far from testing:

battery on tender: 13+ volts
battery off tender: 12.89 volts then drops rapidly (clue)
voltage from power terminal in engine bay to ground on core support: same as battery
voltage at alternator: same as battery

if the voltage keeps dropping before i even run anything i think i might have my answer/have to eat crow/have to call braille

I'll still run the car later on to see if the issue persists with the fan on. I also remembered the tuner changed the low and high speed fan on temps.

low comes on at 175*
high comes on at 185*

I needed some sleep to process things. Feels like I might need a conventional AGM battery instead of this fancy braille race unit.
 

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ttocs

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just because its dropping voltage does not mean it is the battery, it could also be a voltage draw that is causing it. To test the battery you will need to disconnect it from the car and then test it 12 hours later to see if its dropping.
 

Makoto

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After my morning meetings i went back to check and the voltage settled on 12.57 at the battery, engine bay, and alternator so I think we're good so far as the battery seems fine.
Next step is to test for a voltage drop when the fan hits at the alt and the fan itself.

After watching some videos of some 99 cobras i'm convinced of what ttocs said. The fans shouldn't lug the electrical system so hard. Those cars idle at 700-900 rpm all day without issue.
 

Makoto

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lunchtime update:

alternator voltage is good (14.66 volts, dropping a few tenths as it heats up) when everything is running, even the fan, but when that sucker kicks on the engine idles for a few seconds then putters out.

does the same thing with all the accessories off as well. Definitely something in the fan circuit.

cranks right back up every time.

my next step is to unplug the fan and hotwire it and run the car with everything + fan on.

if it can handle that then that might indicate the issue is in the fan circuit itself.
 

Makoto

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findings:

1. voltage reading at the fan power is 9.9 volts
2. voltage reading at ground .10 volts
3. reading at alt 14+v

so i disconnected the fan entirely and hotwired it eliminating the CCRM circuit completely

4. readings with fan hotwired directly to battery: SAME. losing 4 volts. not sure what this means.

seems like its the fan itself but on the other hand why am i reading less than 14 volts before the fan consumes it? seems like i'm losing 4 volts elsewhere in the circuit.
 
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ttocs

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I thought the harness going to some fans was known to get hot and melt causing some connection issues. Its either that harness or the fan.
 

Makoto

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I used totally different wires. hotwiring it got the same result.

more findings:

1. pulled every fuse to any system unrelated to the car actually running
2. with nothing on, the fan on, when i stand on the brakes (which feel kinda squishy tbh) the car will die at idle
 

96blak54

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I think iac Tps maf are ecu 5v
Fan ecu fuel pump relays are in a housing
I would raise idle speed to were it was before?
Misunderstood
Perhaps my explanation wasnt elaborate enough.

If the air intake draws air from the engine bay...under the hood and the fan kicks up, the fan will cause a deviation in pressure skewing maf readings especially at idle. Not seeing the engine bay, this is solely an idea. Also im sure the tuner had the hood raised while tuning and this wouldnt have cause pressure differences.
 

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