1995 Volvo 850 misses and stalls - rarely
 

I have a 1995 Volvo 850 that dies on the side of the road every few months.

I've worked hard at determining WHEN it does it.

Here's how I get it to happen:

1. Start from cold and let idle for 9 minutes
2. Accelerate under load
3. Engine misses badly and dies
4. Engine sometimes restarts but will die again
5. Engine eventually refuses to restart
6. Wait 6 hours to get engine to restart

If I let it warm up 15+ minutes, this doesn't happen.

I'm suspecting 5 & 6 are caused by the misses & stall/s flooding the engine. So the important question is what's causing the missing & stall?

The only other clue I have is that there's often a slightly weird/hard start and the idle sounds slightly rough when it's going to "do it".

It's the intermittency and weird temperature window that have me and my mechanic puzzled.

Healthy spark. Good signal from crank angle sensor. Good signal from accelerator.

Any ideas?

I am stumped, but I could believe a mildly affected coolant temperature sensor. Can you reliably give yourself 6 hours for diagnosis? if so that wouldn't be too bad. If it's a turbo, it would be OBDII, and that would also help a little.


One possible difference between 9 minutes and 15 minutes might be open loop vs. closed loop. Maybe.

That's what the mechanics originally thought - with the coolant thermostat opening, allowing coolant into a crack in the engine block.

They dropped that idea when they heard the problem in person, but they're still guessing, so I don't know what it was that made them drop that idea. I'll bring it up.

Do you mean, will it be dead for 6 hours? Yes, but the mechanic thinks that's flooding from the misses/stalls.

Alas, non-turbo. The diag codes complained about the throttle sensor once (possibly an error from long ago). Since resetting it, it's only complained "Idle air control valve signal absent or faulty", but the mechanic was disconnecting vacuum hoses in an attempt to find a clue, so that could have caused it.

I gotta tell you, I have not flooded a fuel injected car EVER. I didn't know anybody thought that could happen.

I wondered about that...

Hmm, so if it's unlikely to flood, what would cause an eventual inability to restart, and then a 6 hour "timeout period" before it could be started again?

Sounds like a temperature-related fault at that point.

They're suspecting the distributor cap which sounds too basic for how weird the symptoms are. Their other next move is to remove the top valve/spark plug cover and have a look there.

I don't see how it could be the distributor cap either.


The temperature gauge works through the ECM, so you should be able to tell vaguely how warm it thinks it is.

The symptoms (assuming the failure mode is not setting codes) sure sound like you're losing fuel pressure, either because of a failing fuel pump relay or fuel pump itself. Tons of threads about how to diagnose this.

Get a new mechanic if he hasn't thought of this already. Find a recommended local indy who specializes in volvo if you can.

Since it's a '95 MY another possibility (though remote based on symptoms) is EGR valve sticking open.