Strange electrical problem

Crazy_pilot · #1 09-13-2007, 02:27 PM

My car decided to start acting up today.

I'll describe the symptoms as best I can, they're odd.

First, waiting at a red light the radio (stock) started to make random thumps from the speakers, still playing tunes. Light goes green, I pull ahead to the next light. The thumping gets worse, so I turn the radio down. The speakers start putting out a short electic noise and the occasional thump, then the radio shuts itself off.

Next the real trouble starts. The light goes green, but when I push the pedal the engine nearly dies. It repeatedly gave short bursts to ~1200 RPM, then stopped firing, but restarted before the engine had stopped turning. It did this over and over, taking maybe 1-2 seconds each time. I managed to get it pulled over and parked.

The car kept running, and after about a minute of this the engine began running normally again. Revving normally, idling normally...I turned it off and started again, all normal.

I get the rest of the way home, but as I'm pulling into the driveway the speakers start thumping again. In the driveway I roll the windows up and close the sunroof, and they're barely moving. Revving the engine to 2-3K RPM has no effect on the window/roof speed. Also, the air bag and ABS light started to light dimly.

I just checked the battery, it reads 12V bang on.

So I'm at a loss as to what this could be. Any ideas?

cruisen_15 · #2 09-13-2007, 04:02 PM

hmm, i had a problem kinda like that, my ecu was messed up, got a new one. maby not your ecu but hey, thats what i can think of...

dannmarr · #3 09-13-2007, 05:44 PM

Check the battery with the engine on. It should read 13-14Volts. If not, the alternator should be checked.

crazyhorse · #4 09-13-2007, 06:03 PM

Being intermittent in nature, if you can use some alligator clips to hold your meter leads, you can monitor the voltages. My bet is that when you get the thumps, bad running, the voltage drops.
It COULD be the crank pulley separating.

Crazy_pilot · #5 09-13-2007, 10:25 PM

Quote:

Originally Posted by dannmarr

Check the battery with the engine on. It should read 13-14Volts. If not, the alternator should be checked.

I'll check that first thing tomorrow.

Quote:

Originally Posted by crazyhorse

Being intermittent in nature, if you can use some alligator clips to hold your meter leads, you can monitor the voltages. My bet is that when you get the thumps, bad running, the voltage drops.
It COULD be the crank pulley separating.

My understanding is that the pulley is two peices, so by separating do you mean the outer circle slipping? I think it's fine, the steering never got heavy.

Quote:

Originally Posted by Trevor

You specifically describe a thump, rather than crackles or other noise. By any chance do you have a high power amplifier and possibly with a back up capacitor installed? If so try disconnecting it.

Several thumps, as well as a whine. I do not have any aftermarket audio components.

Thanks for the replies so far guys, any continuing thoughts would be appreciated!

Trevor · #6 09-14-2007, 02:30 AM

This advice is significant ---- “Also, the air bag and ABS light started to light dimly.”

As the first up option, everything now indicates an intermittent connection and or shorted turns within the alternator. A bench test with the machine cold, may not show this up. It must be accepted that the fault is not permanent when making tests.

Trevor · #7 09-13-2007, 06:07 PM

You specifically describe a thump, rather than crackles or other noise. By any chance do you have a high power amplifier and possibly with a back up capacitor installed? If so try disconnecting it.