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No One Seems To Be Able To Figure Out What Is Wrong With My Volvo 850 - it shuts down while driving

I have a 95 Volvo 850 with 105,000 miles on it and I live at high altitude in Colorado. About two years ago it started giving me a problem. It would randomly shut off while driving. I will all of a sudden not be able to give it any gas and all the lights on the dash come on and the engine shuts off and then I’ll need to pull over. For a while it would start right back up again and it didn’t happen very often so I didn’t really address the problem. But in the last year it has happened much more frequently and now it has become an issue because it won’t start right back up again. Now I’ll have to leave it wherever it is for about an hour and then it will start back up again.

The fuel filter, fuel relay, spark plugs have all been replaced. I took it back to the mechanic and then he changed the crank sensor. This didn’t fix the problem. At this point I don’t want to keep taking it back to him to just pay him to keep guessing. What should I do? Any ideas of what the problem might be?

Does this model still use the infamous ignition module, usually located on the fender wall behind the battery? That booger causes the exact same symptoms you describe when they go bad. And, they are not cheap.


Have you checked fuel pressure?

Any stored fault codes?

When it doesn’t start, I would make sure it’s getting spark. Use a spark tester, not an old plug

If you have a fuel pressure gauge, you could easily hook it up to the rail

Is your car OBD2 compliant?

Do you have the standardized 16pin data link connector in the left footwell area?

Does the underhood emissions sticker state that your car is OBD2 compliant?

If it is OBD2 compliant, it will be a lot easier to diagnose

It was good that you did the tune-up stuff. You got that out of the way, at least.

When the car stalls, does it sputter out, or just die cold turkey?


This could be as simple as an ignition switch or bad ground. Also, as @tester said the ignition module. Fuel pump would also be suspect, and that can be tested easily with a pressure gauge.

Hi all, sorry I didn’t realize people had commented on this. When the car stalls it does not sputter. All the lights come on and I am just not able to give it gas, lose power steering and have to pull over. So I took it to a Volvo dealership a couple weeks ago (the closest one is 250 miles - got AAA for the occasion and I got to spend 5 hours in the car with the tow truck guy ha). Anyways, the Volvo dealership pulled codes and said that the cam position sensor was oil soaked and failing. They pulled the codes and found codes for cam position sensor that have been triggered 44 times. They checked the fuel pressure and it was fine. They test drove vehicle with the fuel pressure guage connected and it never dropped or shifted abruptly without cause. The car ran normal during the entire test drive. (Back home it was doing it to me frequently, like every couple of miles when it started to get really bad.) After test driving they inspected the camshaft poisiton sensor and found it to be soaked with oil. They removed the old sensor and seal and installed a new seal and sensor. I paid $700 for this. I drove the 250 miles from Denver and the car didn’t do it once. Then I get back here and am driving around town and it starts doing it AGAIN!!!

I would like to note because a couple people have brought up in conversation the altitude. I live at 9000 feet. Could this have anything to do with this and can I do anything about this in terms of my car??? Why would it drive fine all the way from Denver and then start doing it again? The car has low miles and I feel like it would last a while if I could just figure out what is wrong! HELP!

You can go to an auto parts store and get the codes pulled if it’s OBD2. Report back with the codes. Otherwise still suspect ignition module or ignition switch.

You’re describing a crankshaft position sensor being effected by heat.

The crank sensor is one of the primary inputs into the computer. These sensors can start to be effected by heat as they age. If the computer loses the signal from this sensor the computer thinks the crankshaft is no longer rotating. The computer then see’s no reason to operate the fuel and ignition systems and the engine shuts off without warning. Then if you let the vehicle sit and cool down, the sensor works again and the engine starts and runs.

Since the crank sensor is a primary input into the computer, it won’t always set a code if it suddenly fails.


You might ask your shop to check out the cam sensor again.

Since your crank sensor has been changed already, then what you might try - or ask your mechanic to try - is to get the car running and heat up the crank sensor with a heat gun or something. If that can get the car to stall, and then cooling it down gets it to crank back up then you’d need to wonder about the new sensor being bad off the shelf (wouldn’t be the first time) or something else amiss that is delivering too much heat to it.

When it stalls is it always - by chance - with your foot off the throttle? E.g. you completely come off the gas to coast?

What I would do - and this depends on how comfortable you are about it - is carry a spark tester and can of starting fluid in the car (and whatever little hand tools you might figure out that you need). These are inexpensive things you can get at any auto parts store. When it stalls and won’t restart you check it for spark. If you have none then you know the search is on the ignition system (see @BustedKnuckles comment above).

The starting fluid gets sprayed into the intake someplace (your mechanic could show you where) and if it gets a bit of choke out of the car (or gets it to start), then you know the search is on the fuel system. This at least narrows it down.

It could still be the crank sensor. I’ve gotten a couple defective ones in my day.


Stalling is a common problem on the 850 with several possible causes. Here’s 20 pages of discussion on the subject:

But I would suspect Tester is right and the new crank sensor (or maybe cam sensor?) is bad.