Random death

[Kristuphir]

So just occasionally, when driving along, at any RPM, it'll be like someone hit the "off" switch. Engine electrical just cuts out, engine dies, and (I think this is important) tach drops to zero and MPG gauge pegs at the high end immediately.

Pull over, switch the ignition off, turn it back on, and the car will start immediately without fail. Occasionally it will even turn back on by itself before I have a chance to get all the way pulled over - this has happened twice, once at high speed and once at low speed.

What's my most likely culprit? Crank position sensor? That's what killed my E34 in exactly the same manner, only it never started again until I replaced the sensor. ECU? It's a 173 and appears to have been added with the brand new engine the car received 8 years ago.

This is a 263K mile car and I've read here that the ignition lock itself can get worn and cause something like this. Now that I think about it, I can remove the key with the engine running. Is it more likely to be this?

Hmm. One of these days it's not gonna re-start and I'd like to fix it before that day comes... In total, it's happened maybe 4-5 times in the month I've had the car.

Plugs, cap, rotor, 02 sensor (not a likely culprit) are all brand new.

[nefarious7907]

Could be the CPS or a loose coil wire or a bad relay.

[Court M3]

I'd say cps

[moatilliatta]

i have had that happen before in my E car. but it takes like 3 minutes of it setting for it to start back up.

[Kristuphir]

All right, a little update here.

Seeing as how it's randomly dying, I figured the best thing to do would be to take a 700-mile road trip in it this weekend. It died 5 times in the first 120 miles, and 1 time in the remainder. Now when this happens, the car won't always start right back up like it did before - sometimes, but not always. Also, sometimes it doesn't want to start after it's been sitting - 1 hour, a whole night, whatever. And I did check all the grounds, which are clean and solid, and I can't replicate the problem by tugging on the ECU wiring or the CPS wiring.

So now that I've had the opportunity to poke around in there while it's not starting, I've come to notice that the ICV isn't buzzing with the key on. I was staring at it on the side of the road, when all of a sudden the ICV started buzzing like it's supposed to, and sure enough, the car started right up.

Then one other time, the ICV wasn't on, and I was messing with wires, etc. to see if anything triggered it. I tapped relays, tugged (lightly) wires, etc. and nothing. But then I gave the whole fusebox a good shove and bzzzzzzz, there went the ICV, car started, off I went.

Does one of the relays in the fuse box control power to the ICV among other systems? Can they go out sporadically like this?

It now occurs to me that armed with this new information, I could go look at my Bentley instead of bugging you guys. But any further explanation from you would work for me too.

The cruise control will just spontaneously stop working, too, like I stepped on the brake - and sometimes won't turn back on. Related, possibly?

[Kristuphir]

hmmmm, bentley: Fuse #10, idle speed, fuel delivery, AND cruise control. heh. hmmmmm.

[dlmpsy]

I had a bad ground that caused the car to randomly die.

[Kristuphir]

Where was it? Because I've checked all the ones I know of and they're clean and tight, as mentioned above.

[thereisnoyun]

its possessed

its possessed yo, take it to an exorcist.

[moatilliatta]

by new relays, see if it fixes it.

[dlmpsy]

I cleaned my grounds and used dielectric grease. I cleaned the one at the firewall, engine/block ground and the one for the instrument cluster on the steering column. You may want to check the connector on the driver's side of the block. While you're at it you may as well clean/grease all the connectors you can find. It's good maintenance even if it doesn't help. As others have said, it could be a relay.

[Kristuphir]

For any interested parties, it was a bad relay.

[delphini]

the middle one right ???

[vivalegreg]

hmmm i would say main relay? one on the far right if looking from driver side (in the black box with the 3 relays)

oh and, if it was a bad crank position sensor....(ie one that doesnt work at all) the car would never start until you replace that sensor. this is because prior to startup, the cps tells the computer the ...position of the crank. this is needed to make sure it has the right timing i believe...

[Sean]

For any interested parties, it was a bad relay.

I know I'm bringing this back from the dead...oh well. I've been having this exact same issue. Mine sounds like it isn't getting ANY fuel. Car sat for four months, and it took my 5 minutes to get it started. But, up until that point, there wasn't a single fire - when it started it roared to life instantly.

Happened again to me last night. Messed with it for about 5 minutes again, pulled out my backseat to see if I could feel the fuel pump operating - then it started up.

Looks like I'll check my grounds and my relays - what exactly was the relay that you replaced?