2G GSX stalls when the fans kick on

[#95GS-EX]

Hi guys,
So i recently had the heads built on my car and installed aem cam gears, my car has a aem series 2 ecu and im having an issue with the car dyeing as soon as fans kick in the car seems to be losing voltage. i have a new alternator and battery so i dont think thats the issue. before i had the heads built the car was running fine.

 

[DSMPT]

Could be a bad fan motor, or have a short or bad wiring in somewhere. Please take a log to see how much the voltage would drop while it happens. The engine runs fine until the fans get turned on, correct?

 

[#95GS-EX]

yeah engine runs fine until i start turning on electronics on the car or when the fans kick in

 

[waltah]

Sounds like a bad ground or other shared pathway. I would check the battery voltage right at the fans and also right at the battery at the time when the fans kick on. You're looking for some lost volts at the fans and also other things like maybe the ECU or ignition system.

 

[#95GS-EX]

car has good ground. I've heard some people run a cable from alternator straight to the battery but that does not seem to make a difference

 

[DSMPT]

until i start turning on electronics on the car or when the fans kick in

You have to be more specific. How and when exactly does it stall? It seems it's not only happening when the fans get turned ON. What happens if you turn ON the A/C, headlights etc? Does it stall quickly or slowly? Does engine still stall if you are opening the throttle a little bit when the fan turns ON?
Please upload a log while it is occurring.

before i had the heads built the car was running fine.

Have you changed the cams?

 

[#95GS-EX]

You have to be more specific. How and when exactly does it stall? It seems it's not only happening when the fans get turned ON. What happens if you turn ON the A/C, headlights etc? Does it stall quickly or slowly? Does engine still stall if you are opening the throttle a little bit when the fan turns ON?
Please upload a log while it is occurring.

Have you changed the cams?

yes the cams were changed and the car only dies out when its at idle not if I'm giving it throttle. I have also been told it could be the alternator but i just replaced it a few months ago

 

[#95GS-EX]

yes the cams were changed and the car only dies out when its at idle not if I'm giving it throttle. I have also been told it could be the alternator but i just replaced it a few months ago

You must be logged in to view this image or video.

 

[Mello]

What the manufacturer of the alternator? Where did you get it?

 

[DSMPT]

yes the cams were changed and the car only dies out when its at idle not if I'm giving it throttle. I have also been told it could be the alternator but i just replaced it a few months ago

Could be the alternator, could be the cams (not cam gears), could be the tuning... Please upload a log.
As I understood, this wasn't happening before rebuilding the head with the previous cams, correct? If so, what cams did you have before and what cams do you have now?

 

[#95GS-EX]

ac delco 75 amp

 

[#95GS-EX]

Could be the alternator, could be the cams (not cam gears), could be the tuning... Please upload a log.
As I understood, this wasn't happening before rebuilding the head with the previous cams, correct? If so, what cams did you have before and what cams do you have now?

it was all stock

 

[DSMPT]

it was all stock

What cams do you have now? And you know the car has a AEM EMS, I don't know why you don't take a log.. I have already mentioned it 3 times. At least you can easily see if it's a voltage drop issue or not.

 

[#95GS-EX]

I will log and update results

 

[We're on Boost]

How many fans are on the car? Do you know how many amps they are rated to take from the system?
Also, be sure that the ground wire from the firewall to the intake manifold is in good shape. I think I see the firewall end of it in your picture in post #8 so it's apparently there. But it's one of the things that would be removed when doing the head and sometimes people forget.

 

[steve]

Make sure to get whatever the AEM version of ISC steps in the log and the idle switch.

 

[Mello]

Try re-installing your calibration file.

 

[#95GS-EX]

Issue fixed I needed a new alternator with more amps. Thank you guys for all your help

 

[waltah]

Issue fixed I needed a new alternator with more amps. Thank you guys for all your help

That might not be a complete fix. On few cars will the alternator alone carry the full maximum load when idling. The battery has to pick up the difference. If your battery isn't able to do that when roughly fully charged then either the battery is weak (either old so it won't take a full charge or healthy but discharged) or something else is wrong -- most likely a wiring problem.

If you know you have a weak battery or that it was run down when fans killed the engine then you may have a complete story. If you can put the battery on charge when not driving that might help.

Otherwise I'd keep on studying the thing. Battery or wiring problems like this almost always bite you eventually.

Standard alternators tend to be a little undersized because of fuel economy and cost. Unfortunately it's tricky to upgrade the power because the pulley setup in our cars makes it hard to get enough tension to control squealing on starting with a high output unit.

 

[#95GS-EX]

That might not be a complete fix. On few cars will the alternator alone carry the full maximum load when idling. The battery has to pick up the difference. If your battery isn't able to do that when roughly fully charged then either the battery is weak (either old so it won't take a full charge or healthy but discharged) or something else is wrong -- most likely a wiring problem.

If you know you have a weak battery or that it was run down when fans killed the engine then you may have a complete story. If you can put the battery on charge when not driving that might help.

Otherwise I'd keep on studying the thing. Battery or wiring problems like this almost always bite you eventually.

Standard alternators tend to be a little undersized because of fuel economy and cost. Unfortunately it's tricky to upgrade the power because the pulley setup in our cars makes it hard to get enough tension to control squealing on starting with a high output unit.

Thanks and yeah the battery needed to get swapped out also. Car is running like a champ now.