850 randomly loses power and dies

[Derry]

1996 850 Estate 2.0SE Auto

The car starts ok, idles normally, drives ok but sometimes it suddenly looses power all dash lights come on, lambda flashes and just turns off. I loose breaks and power steering. Turn key to 0 and turn back and starts ok, sometimes hesitates but starts and drives again, and can do 5400rpm and drives very smoothly in any gear selection.

It’s a shame as this is a major issue as we live in a hilly town and the issue happens without warning. Once it happened going down a hill (no steering + break)

I have replaced the fuel pump relay, the vacuum hoses replaced, battery fully charged. No codes on the DIY flash code reader just 1-1-1.
Been using the car for past 13 years, and with this forum's help have kept it going.

Any help or suggestions as to what could be or where I should look will be much appreciated.

[Martin Cox]

I'm no expert but could this be related to the electrical part of the ignition key assembly? The switch is known to wear and all sorts of odd things then happen. I believe the switch part can be fairly easily replaced.

Martin

[Derry]

Just to update the issue was with coupling piece / vacuum elbow going in the bottom of the throttle body which had very tiny cracks. I had noticed it before but wouldn't have thought it would be responsible for getting the car to loose power.

[Clan]

Originally Posted by Martin Cox

I'm no expert but could this be related to the electrical part of the ignition key assembly? The switch is known to wear and all sorts of odd things then happen. I believe the switch part can be fairly easily replaced.

Martin

It could well be ! next time it happens , twist the ignition key a bit back and forth and see if it comes back .....

[Derek UK]

It might have lost power but why should it have caused the loss of electrics?
That might have been a red herring and is indeed related to the ignition as mentioned.

[rickyghib]

Had the same thing happen in my 850 glt in 2019. Pretty scary when you've no brakes and no power steering in those big lumps! Happened about 5 times, each time was when I hit the brakes hard(ish). Always started up fine afterwards, and didn't have the money at the time to get it checked.

Eventually, had it resolved by local mechanic- i'm no expert, but from what he told me it was a vacuum issue.

[Derry]

So after a long absent the stalling issue is back. I was suspecting vacuum leak issue, but it idles perfectly hot/cold, I did a carb cleaner vacuum test around the manifold and hoses like this guy (https://www.youtube.com/watch?v=9CPqbaSgcok).

You do get a 5 to 10sec warning when it about to go, giving you enough time to start planning to pull aside but main worry is that I lose power steering and breaks going down/uphill Within this few seconds I try flooring it but no difference.

All the warning dash lights come on and do have electric.

Would it be the MAF sensor? Probably could do with a clean.

Is there something I can test or do when it happens to narrow down the cause? I try the LED code reader and still just 1-1-1 and it starts up fine after a minute or so and drives OK for miles.

[Laird Scooby]

Originally Posted by Derry

So after a long absent the stalling issue is back. I was suspecting vacuum leak issue, but it idles perfectly hot/cold, I did a carb cleaner vacuum test around the manifold and hoses like this guy (https://www.youtube.com/watch?v=9CPqbaSgcok).

You do get a 5 to 10sec warning when it about to go, giving you enough time to start planning to pull aside but main worry is that I lose power steering and breaks going down/uphill Within this few seconds I try flooring it but no difference.

All the warning dash lights come on and do have electric.

Would it be the MAF sensor? Probably could do with a clean.

Is there something I can test or do when it happens to narrow down the cause? I try the LED code reader and still just 1-1-1 and it starts up fine after a minute or so and drives OK for miles.

CARB CLEANER IS NO GOOD FOR THIS TEST IN THE UK!!!!!!!!!!!!!!!!!!!!!!!

Eric the Car Guy is USA based in case you hadn't guessed by his accent. Stateside they still have aerosols that use VOCs - we don't!

As such, anything that is recommended to try and alter the incoming mixture by spraying it into suspected leakage holes won't change things one bit!

The only thing that will is WD40 because it is a petroleum distillate so will in fact burn.

I would look at your cat and/or exhaust for a loose baffle inside a silencer, loose honeycomb in the cat that can move and cause a blockage etc. Restarting will cause some vibration and movement and likely clear whatever it is and besides, it should rev higher than 5400rpm unless it's a diseasel which from your posts i don't think it is.

I'd also check your air intake very thoroughly from throttle butterfly to the furthest point from it where the air first enters the intake trumpet to the air cleaner including the filter. It's not unknown for the air filter to collapse and cause blockages that would result in instant loss of power.

[PNuT]

check the wiring that goes into the relay on top of the radiator...

Can you hear the fuel pump running when it is a problem?