rpm dips and voltage drops

[akirony]

Re: rpm dips and voltage drops

Well I dnt know why but it does it more in colder weather. It only does it under 1k rpms and the lowest drop was to 450 rpms. Its running off the MAP sensor only and it feels like Ive gotten more power at the ALT expense

[LETZRIDE]

Re: rpm dips and voltage drops

I did the mod Robert sent me with the wires, made a bit of a difference, but it still has the issue, just not as bad.

I think there is a table that can address it in Tiny tuners, I just need time to get that program up and running again to investigate a little further. That and my car is in winter storage at the moment, so I can't try much else.

[akirony]

Re: rpm dips and voltage drops

Well I checked my charging system and the printout shows high voltage at 14.72V no-load and 14.61V with load. Alldata says if its not the alternator to check the pcm but I wouldnt even know where to start doing that esp since my dvom just took a crap with a new battery and both internal fuses. Anybody think that there is a pcm reflash? Ill go to the gm dealer tomorrow on my lunch break to ask them.

[LETZRIDE]

Re: rpm dips and voltage drops

There is a reflash, but I doubt that will do anything for you. I've reflashed my pcm everytime I tune, and I still have the issue.

[akirony]

Re: rpm dips and voltage drops

This is what it says for a 3.8L firebird pcm controlled generator. (The generator provides voltage to operate the vehicles electrical system and to charge the vehicles battery. A magnetic field is created when current flows through the rotor.

This field rotates as the rotor is driven by the engine, creating an AC voltage in the stator windings. The AC voltage is converted to DC voltage by the rectifier bridge and is supplied to the electrical system at the battery terminal.

The operation of the charging system is monitored by the PCM. The PCM monitors the charging system loads and adjusts the idle speed accordingly. The PCM also sends information to the Instrument Panel Cluster (IPC) when the charging system is inoperative and tells the IPC to illuminate the volts telltale lamp.

The PCM supplies 5 V through the L circuit to the generator. If the generator becomes inoperative, the PCM can detect the fault through the L circuit and tell the IPC to illuminate the volts telltale lamp.

The PCM also monitors the duty cycle of the generator through the L circuit. As the generator load increases, the PCM will adjust the idle speed accordingly. If the IPC does not see any activity from the PCM the IPC will illuminate the volts telltale lamp.

If the Voltage telltale is on and the (L) terminal voltage is low while the PCM is commanding the generator on for more than 30 seconds OR

If the Voltage telltale is on and the PWM is less than 5% while engine RPM is less than 2500 for more than 30 seconds DTC P0620 will set.

If the Voltage telltale is on but no DTCs are set, use the PCM Controlled Generator Diagnosis to diagnose the problem.

Generator Assembly
The generator assembly is mounted to the front of the engine on the passenger side of the vehicle. The CS-type generator uses an internal regulator which features built-in fault detection. The generator used on this vehicle, is not to be disassembled for service.)

Im thinking that the pcm is missing something from seeing the 5V to the alt and thus causes the rpms to dip in a way to try and keep up with the alt or vice-versa. I checked my 5V circuit but was only getting 4.8V. A friend at work seems to think that the difference is minor but I dont know. If I check for 5V I expect to see 5V yaknow. And if not then Id think something is wrong. You dont think that having leds would cause any problems like this do you? Since they use less energy the pcm might have a hard time seeing their usage on the circuit and overcharges the alt. My mazda knowledge is failing me here.