1997 S40 Random Loss of Power

TheBBG · Post by **TheBBG** » 25 Oct 2015, 17:59

Recently the vehicle (2.0 automatic) started exhibiting random loss of power and missing that would be symptomatic of bad fuel or water in the fuel. The servicing shop checked the fuel system and found nothing amiss, and there are no error codes. We have tried E10 in case it was moisture in the fuel as well as injector cleaner, no joy. It will run well for a few days and then act up for a few 10's of kilometers, run well for a few, and stumble for a few randomly. There has been a tank+ of fuel used since the first episode. It does not seem to reflect speed or temperature.

The original observation was that it happened going uphill with a partial tank of fuel, suggesting fuel quality, but over time it is doing it regardless of angle and fuel level.

Any suggestions how to proceed? An obvious approach is to drain and clean the fuel system regardless that there is nothing apparent, and then to move on to sensors one by one, but the cost would quickly approach the value of the vehicle since we are unable to do this ourselves.

Thanks for any insights or suggestions,

TheBBG · Post by **TheBBG** » 30 Oct 2015, 00:33

It is increasingly looking like something in the fuel tank could be interfering with the fuel pickup. Is the fuel pump inside the tank and if so does it mount through the top so it can be removed from the boot/trunk?

Post by **alschnertz** » 30 Oct 2015, 14:47

I've got no experience with a 2.0L, (mine's a '01 1.9L turbo) but did you monitor the fuel pressure under these circumstances? It should be pretty steady around 44 psi or so.

In my opinion E10 is awful fuel and I wouldn't use it in hopes that it would eliminate moisture. It actually absorbs moisture. We have no choice but to use it here in CT. I was a small engine mechanic for a few years and it's incredible the damage that that fuel does to small engines. It's so bad that I now use fuel stabilizer in anything I own that uses gasoline - cars included.

As for the fuel pick-up. In my '01 S40 sedan, it is accessed under the rear seat. Very easy to get to.

TheBBG · Post by **TheBBG** » 30 Oct 2015, 15:23

Thanks for that

In Australia the fuel drying additives common in the US do not seem to exist so E10 seemed a reasonable approach to address possible moisture. We normally would not be using it. My understanding is E10 essentially atomises moisture so it does not affect running as it goes through in relatively minute quantities/concentrations. I don't have any way to monitor fuel pressure but the pump was replaced last January and the fuel filter again, very recently. Still a bit of evidence collecting to do and if it continues to suggest something affecting the pickup, I expect the pump access will be under the rear seat since the chassis should be identical. I would have expected a computer error code for fuel pressure, but apparently not. Cheers,

Post by **alschnertz** » 30 Oct 2015, 19:22

New pump in January? Hmmm. What brand?
I replaced my fuel pump last November with a new aftermarket pump because it was so much less expensive than a factory pump ($100 vs. $350). It died the following July. I bit the bullet after that experience and purchased a Genuine Volvo pump.

It's not difficult to monitor the fuel pressure. You should be able to hook up a gauge to the schrader valve that is on the end of the fuel rail. There is no pressure sensor for fuel pressure, hence no codes.

TheBBG · Post by **TheBBG** » 30 Oct 2015, 20:20

The replacement pump was not OEM. It was replaced because of vapour lock in very hot weather (above 38C). The current symptoms are much different. What started out to appear random might be starting to converge. Thanks for the pressure info. Will be worth a look if the 2.0 non-turbo is configured the same re the schrader valve.

Cheers,

TheBBG · Post by **TheBBG** » 08 Nov 2015, 22:31

For the helpful and curious, best guess is it is not the fuel system as no fuel anomalies can be found. Maybe an errant sensor that is putting the engine into a limp home mode, but would expect an error code from that.

TheBBG · Post by **TheBBG** » 13 Nov 2015, 15:01

The problem was resolved by replacing the spark plug wires and a coil. The technician said it was not an obvious one considering how the symptoms manifested. It was a stroke of good luck it decided to stumble and keep playing up while he was looking at it. Case closed.

Post by **alschnertz** » 14 Nov 2015, 07:02

Congratulations.
I had a coil go too. No codes for years, but a miss at WOT only that I couldn't pinpoint so I let it go.
Finally got a code and changed the coil. Wow, what a difference. Never realized how much "scoot" the car had.