Can't figure out where to post this so if this is wrong my apologies. I have a Monster Miata with a SBF 302 EFI with an A9L ECU. If the car gets up to temp and the fan kicks on teh car starts to missfire and hestitate badly. I can recreate this by turning on the A/C which kicks the fan on too. I'm really not sure where to start troubleshooting this right now. Any ideas? I was thinking of wiring the fan up manually and see if that does it and if it does maybe its a ground wire issue somewhere?
You’ve come to the right place with your question, and just dropping this here: How to solve common electrical issues with only a test light.
What is your coil's primary voltage when the fan or AC is running? At first guess, it sounds like the ignition is breaking down due to low voltage.
That's the first thing I thought of. Where are the fans getting power?
check grounds. make sure they're clean and tight. giggity.
Confirmed voltage drops form 16 to 14 when the A/C kicks on or the fan kicks on. With RPMs teh voltage creeps back to 16 but I'm still getting misfires and hesitation. Gonna look for the grounds tomorrow.
It shouldn't be at 16 anyways. Sounds like the voltage regulator in the alternator is fried. Is it the old school case or a 3g?
How old is the battery?
I have seen bad batteries create similar symptoms where charging cannot keep up with system demands.
Are you testing system voltage (like batttwry positive to ground)? Or coil voltage (like coil + to coil -)?
If the fans are using the same ground as the coil and there is a problem with it, turning the fans on may increase the relative voltage on the ground side of the coil, reducing the voltage across the coil significantly.
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