1G Car randomly loses power, makes rapid relay-like clicking sound

[XC92]

My Talon's had this intermittent problem when suddenly there's either no power at all, or just barely enough to turn on dash lights but not turn over the engine. This is after the car's been driven a while, so assuming the battery, alternator and wiring between them is ok, it's not lack of power or charging.

Note that the car doesn't shut off while being driven. It just won't turn back on after it's been turned off, like when I have to stop somewhere and leave the car for a few minutes. What I've done is use a power bank jump starter to get the car running again, which usually works, but sometimes there will be this clicking sound that seems to come from under the right side of the dash once the car is moving again (although I hear a similar sound when I'm by the battery giving it a boost, like from the idle control servo or EGR valve, or perhaps ABS) and the car will sort of jerk in sync with that, so I have to pull over.

Any ideas? Bad relay or fuse? ECU? Loose wires? Maybe the alternator isn't charging as well as I assume it is. This happened tonight some distance from home so I had to get a tow and it was too late and dark to do any diagnosis but I'll have a look tomorrow. Meantime, do these symptoms resemble any common issues with these cars? It's been an on and off thing for several years now.

Two other things just occurred to me that could relate to this. Well one definitely does. As this was happening tonight, the check engine light came on. I was unable to read the code but will do so tomorrow.

The other thing is that the car's been idling somewhat rough, and often shut off when driving really slowly in 1st or reverse (it's a manual), like when parking or getting out of a tight parking spot and I have to go easy on the throttle and feather the clutch.

One of the tire's also got a very slow leak so maybe the air was low enough to throw off the ABS ECU and cause this?

I'll check what I can tomorrow and do some research, but if anyone has any ideas I'm all ears.

 

[wparks]

Personally, I'd start by eliminating the battery and battery cables right off the bat. I see a lot of funky stuff like this when a battery is sulfated and not holding much charge, or the battery terminals or cables corrode, or the posts glaze over, and you get an intermittent connection- Can prevent proper charging, and can give flaky intermittent problems like this when trying to start or run at low RPM (when the alternator is not putting out a lot) and the battery voltage dips low. I have seen it die, codes thrown, and make perfectly respectable mechanics look foolish while overlooking this problem because it is so unpredictable and intermittent.

Check and clean the connections in the positive side cable- specifically between the post connector and the fuse assembly that bolts to it- corrosion can get in between those parts. Then, use a battery terminal cleaner to clean the battery posts shiny, and the insides of the cable connectors shiny and make sure they clamp to the posts tight. Take a drive- any improvement? If not the battery may need a good cycle on a battery charger or drive long enough to bring it up to full (hour or more).

If the charging system is working properly and has good connections to the battery, you will see the following: Before you start and drive the car in the morning you should be seeing 12.5-12.6 on the posts after sitting and settling all night. Once the engine is running, the alternator will be charging and you should see 14.2-14.6 depending upon temperature and other variables. I like to measure voltage on the lead posts themselves, not on the connectors. If you see the proper charging voltage while running, but in the morning the battery has dropped much below 12.4 you likely have a badly sulfated battery that needs to be replaced. Sulfation happens when a battery sits discharged for a long time, or is not getting enough charge over a long period due to bad connections.

Once you are sure about this, then it's time to dig deeper.

 

[XC92]

So...had a look at things today. First I checked the battery's voltage, before trying anything. At the posts it was around 12.25-12.28V, which was low but understandable and acceptable given that the starting and running issues I had last night which ran down the battery.

The car didn't start though, or even turn over. Just a single relay click, and everything was dead.

Readings taken on the terminals gave similar values, BUT the readings fluctuated, not within this narrow band but from it down to single digits or lower, indicating contact or corrosion issues. Since there didn't seem to be corrosion, I thought it might be poor contact.

And what do you know, the negative terminal was slightly loose, and when I tightened it, everything was fine, the car started as normal, very little hesitation (explained by the slightly low voltage), and kept running, as normal. So I hope this was the issue.

Of course as with all older cars, there could be other issues with the electrical system, and when it's warm enough I'm going to give everything a more thorough look-over and fix or replace anything that seems sketchy or is past its sell-by date.

But for now, I THINK I solved the most proximate issue and can drive again. Closer to home for now, until I'm assured that it's all good. And thanks for the tips!