Engine cuts out

rangema · Post by **rangema** » 20 Sep 2010, 14:38

My '98 S70 non turbo (280,000 km)has been hesitating occasionally over the last few months and recently the engine cut out entirely twice during low speed city driving. After a moment or two rest, the engine starts and runs normally for days or weeks without any symptoms. Then the slight hesitation may be noticed again. Fuel pump going bad, MAF sensor???
Thanks
Marc

Post by **charlyW** » 21 Sep 2010, 03:35

Does your car cut out mainly as you come to a stop ? Try cleaning the MAF with good carb cleaner, seems theres a fuel issue going on over here in the UK after a month of snow and ice 98% of the 850's and V70's had a similar issue at a guess its the change of fuel as the companies add more or less Ethanol in the mixture for winter. It might not hurt to check the fuel relay

I could be completely wrong on my thoughts just cleaning the MAF's over here in the UK solved 99% of the 98% issues

Skottynan · Post by **Skottynan** » 21 Sep 2010, 18:06

Tune up time?

rangema · Post by **rangema** » 29 Oct 2010, 21:15

Cleaning the MAF and Seafoam in the gas seemed to help ... for the next 5 weeks, then the engine cut out again last Tuesday. This time I noticed very erratic fuel consumption numbers (on my Scan Gauge) when I got it running again. If I keep the revs above 2000 rpm, it doesn't cut out. I have never had a check engine light and there are no codes. I thought I had a hard fail but the next day the car was running beautifully again. All indications normal.
For the last few days the car has been running normally.
Intermittent faults are a drag. Any ideas anyone?
Marc

Post by **jreed** » 30 Oct 2010, 05:33

+1 on CharlyW's suggestion that it could be the fuel pump relay. There could be a bad solder joint(s) or a bad electrolytic capacitor that is causing intermittent failure and shutting off the fuel pump. These might not be the cause of the problem, but they can be addressed for low money (<$4 for two high-temp rated capacitors from DigiKey) and not too much time. Good luck!

rangema · Post by **rangema** » 31 Oct 2010, 10:12

The relay will be the first In my search for the culprit component. Who knows, I may get lucky. I have 45 psi at the fuel rail and the pump runs without any noise so if intermittent fuel pressure is the problem it may well be the relay.
Thanks
Marc

rangema · Post by **rangema** » 13 Nov 2010, 19:14

So, new fuel pump relay, MAF and all connections cleaned again and still no joy, however. Last Thursday, drove to town and the car frequently stalled and threatened to stall after getting to town. I got back home by keeping the revs up and putting the car in neutral at lights and when the traffic slowed. The next day I made the identical trip at the same time , same temperature and humidity and pressure, same traffic and not a single hiccup. Hmmmmmm???
I did notice that if I advance the throttle to about 2,000 rpm and hold it steady, the revs will rise to 3,000 t0 35,000 rpm without any throttle movement. I checked it often to make sure it was not a throttle cable issue.
What do you think? Throttle position sensor?
Thanks
Marc

Post by **jblackburn** » 13 Nov 2010, 19:29

35,000 RPM? Your cylinders would be in orbit around the Earth

Could be a bad idle control valve since it doesn't sound like it can idle. It doesn't suggest being either a cam sensor or crankshaft sensor if you can hold the revs up and keep it from stalling.

If it seems like it is smashing between gears a lot, or flashing the upshift arrow at you, that would suggest a throttle position sensor. The engine should be able to maintain idle speed without that, though.

rangema · Post by **rangema** » 14 Nov 2010, 11:30

Oops, one too many zeros. Thanks for the advice. No smashing or upshift arrows. I guess I should be looking for an idle control valve.
The engine maintains 840 rpm at idle most of the time, as viewed on my scan gauge. The car's tach shows around 900 - 1000 rpm at idle.
When acting up, if the engine doesn't actually cut out, the idle will vary (hunt?) between 810 rpm and 900 rpm.
Could the idle control valve be intermittent like that, good one day and bad the next?
Cheers
Marc

Post by **jblackburn** » 14 Nov 2010, 13:15

Yes, but so could a bad mass airflow sensor which is what I'd suspect first. The IAC valves rarely go bad.

Unplug the MAF and drive around for awhile; does it act any better?