Hello!

Posting out of desperation. Long post warning. I want to give as much detail as possible - we have already replaced some parts and the problem hasn't been solved.

V70-97, petrol, automatic. First stall in traffic out of the blue about a month ago. After a longer highway drive in hot weather, going uphill at low speed, turning sharp right, very noticeable RPM drop (as if I had downshifted), then it goes up and down several times, and stalls. from zero to stall in about 10 seconds. No CEL. [I didn't try to restart it right away because I was in shock. It was my first time ever, a car stalling on me while in traffic. Ten minutes later it restarted just fine and drove it home without any problems.]

Car had driven perfectly fine before this, in fact, I moved with the car at highway speeds over ca 4000 km in the preceding few weeks and I didn't notice any problem. I've never had rough idle or any other hiccups before. New ignition everything a year ago; recent oil change; new fuel filter ca 30.000 km ago. Less than a year old, fully charged battery.

No car driving for two weeks after this (frankly... I was in shock). I spend my spare time reading forums. On a whim, I decide to replace the fuel pump relay which turns out to be original from 1997. I'm pretty sure I solved my problem. I'm so proud of myself!
Confident, I resume driving and it drives just fine for 8 days. mainly short distances (up to 10km), in town, no highway speeds. Everything feels fine.

On day 9, driving at highway speeds for the first time, short distance (ca 15km), hot weather outside, engine surges at full highway speed, RPM up and down for some 10-15 seconds. Scary. I can barely get off the highway, stuck between two trucks. Taking the magically appearing exit (just on time!) and stalling out at the first roundabout. Car restarts immediately, drives home generally speaking OK. I let it idle in front of my home and it stalls again within one minute of idling. Restarts immediately but with a "lambda" light and the idle feels very rough!

I'm in Sweden. I contact the first (non-Volvo) workshop for error code reading - the one closest to me because I'm actually afraid to drive the car any longer. We decide to drive the car there with the CEL on the whole time. Car feels sluggish, but gets there without stalling. Feels like I'm driving in honey.

Workshop finds no relevant* error code and returns the car saying everything is fine. They don't do any manual check, just strictly OBD2 reading. They reset the CEL. They take my money regardless. They give me no explanation whatsoever as to why the CEL was triggered if I, I quote, have no problem whatsoever with this car. [*There's only one they find: DTC 231 - Adaptive fuel trim too lean or too rich in part-load range -- they tell me it has nothing to do with the stalling]

I don't even go home. I know I do have an issue and I want it to be found. So I take it to a Volvo workshop right away instead (in town). With a list of suspects I compiled with the help of a friend (see below later) and online forums. I ask them to go through it in detail, especially if they find no error code. I tell them I don't want to get my car back without some kind of explanation again.

Next day, they do zero manual leakfinding either [despite my explicit request), only code reading. There's no code!! They test drive the car which stalls on them once in highway traffic but the engine restarts right away. They fiddle with the keys figuring the ignition cylinder is worn out (I'm guilty of driving with a bunch of keys for years) and decide to replace it. They test drive again and it doesn't stall (ca 20 minutes on the highway). [b]They return the car to me telling me they've solved my problem. [I understand how the worn ignition cylinder can cause the stalling but not the CEL and the rough idle. I get no answer to my questions. They're done with me.]

I don't trust them. I don't trust them because they didn't even do what I asked them to do, with a voltmeter etc. I contact a friend again who has some solid car mech. background but lives quite far from me. He suspects camshaft or crankshaft sensors (which were on my list I gave to Volvo). I'm scared... Anyway I drive there on some smaller roads, carefully avoiding the highway, without any issues (ca 90km) across a wide speed range, anywhere from 40km/h to 120km/h. No surge, no stall. We're perplexed...

He agrees to check my car manually. We test drive and get three smaller surges spread apart over 20-25 minutes. Only one surge every time and it resumes immediately, no stall. He asks me about how and where I'd been tanking lately. We deduce that I must have gotten bad fuel (trainees at the gas station mixing in some diesel or similar issue) and that I now get smaller surges and no stall because I'd just diluted down the "bad fuel" by tanking before visiting him (I tanked ca 30L on top of the existing 10L). We test drive and top up the fuel, so now the original "bad fuel" (if it was that) is diluted down to ~1:6. We also add some fuel system cleaner and he replaces my fuel filter (at that time I wasn't aware that it had been replaced just 30k km ago). As we test drive, car begins to have a constant, little, but noticeable "drag" and tiny surges. He explains it as though the bad fuel is now being flushed out.

I leave late in the night, thinking that now with the fuel cleaner once I get through this tank, all will be fine. I don't get far: car stalls out after only 3km at ca. 80km/h... same thing as my original problem but more intense than ever before. Huge RPM drop, all lights up, engine stalls within seconds. Engine insta-starts again but will drop the idle right away to zero and stalls again with a CEL. I try several times, same thing, idle drops right away, complete stall -- looks like this car not going anywhere anymore.

I give up. I call him. He comes in some 20 minutes and when we try to start it up again. By then, it starts up and we drive back home (only 3km). Car feels sluggish and without power. Nonetheless, he decides to test drive some more because he wants to see himself just how it fails so off we go again. Within the next 10 minutes, we get the surge and the complete stall. CEL is on and the car will drop the idle right away, multiple times. We wait some 10 minutes, restart, and get home with the very, very sluggish car.

He now suspects either camshaft or crankshaft sensors. Removes camshaft sensor and checks it with a voltmeter. Turns out the wire is broken (measures XYZ value first, then zero resistance when in a different position) so he replaces it.
We test drive again in the night. It's flawless! We're pretty positive at this point that the problem was the camshaft sensor and that we're all good. Still, I stay for the night, planning to leave only in daylight, just in case.

I ask him to test drive again the next morning before I really sit in it and go home. He drives ca. 35km up to 160km/h and it's flawless. He returns it back to me also telling me that my car feels much different now, it's much more powerful, like "new".

I sit in the car to drive home, confident that it was indeed the camshaft sensor, or rather, its wire. I drive home all the way over 75km - mainly highway this time - and it's flawless. It's responsive, it's snappy, no residual sluggishness whatsoever. It accelerates just like before. I'm loving it!

Until... 10 meters from my house. Uphill, low speed, huge surge, all lights up, stall!! CEL is back!!
Insta-starts again and I do the last ten meters to park. I stop the engine. I start again several times. I'm nervous. CEL has disappeared!!! No CEL! But it drops the idle 5 times out of 6 I try and stalls out within 4-5 seconds. I smell fuel while still sitting in the car. The sixth time it doesn't stall out but idles very, very rough. I stop it after 2 minutes or so.

I'm done for the day... I come inside, contact my friend, tell him what just happened, and decide to register here for advice...

I need help. I must move next week. With this car. Another 1300km.

Thanks for reading! Any further details, please ask. I really appreciate any input.

PS. Please try not to use too many abbreviations. I've been reading car forums for weeks now but I'm a female and not a car mech. I have engineering background myself but next to zero experience with cars, other than the end user experience.

PPS. Crankshaft sensor: voltmeter was reading constant resistance any way we were moving it around so he concluded it was good. [Is it so? I remember reading somewhere that the crankshaft sensor can be tested reliably only with a scope...?)
Air filter isn't clogged. He said it was okay.

 

Additional info:

I've been driving the car for the past ten years without any engine-related problem.
It's a turbo engine.
Mileage ca. 257k km.