Random Stalls at speed 98V70

Etheraldreamer · Post by **Etheraldreamer** » 07 Oct 2011, 14:05

I recently replaced the fuel pump in my 1998 AWD V70. I also left off the rear drive shaft after this repair to convert the car to FWD only in hopes of seeing a couple more MPG...

Since that repair, during the first week I didn't notice anything too out of the ordinary, a slightly rough idle, and that was it. I figured it was crap that got into the fuel lines and planned to run a cleaner.

Before I got the chance however, it started to clear up and idle smoother... After a day of nearly perfect running, the following day it decided to just die while travelling on the interstate. I was going about 60mph and slowly my RPMs started to drop to zero, with the fuel pedal having ZERO effect on either RPM or speed. After rolling to a stop I put it in P and it started right back up. I drove to the autoparts store and got a can of seafoam to dump in a fresh tank. It's been about 100 miles since then without incident. That is until this morning, when it did it again. No warning, no signs of struggle, just a random plummet of the rpms to zero, where I coasted to the side, started it up on the first crank and continued 40 more miles without a hint of a problem...

It concerns me because I live about 60 miles from work and this is my daily commuter. As of now it's started immediatly both times it died, but I want to figure this out before I am really stranded. Any ideas?

Thanks.

Etheraldreamer · Post by **Etheraldreamer** » 07 Oct 2011, 14:09

Also, not sure if its relevant or not but there have been a couple times when coming to a stop that the car just wants to stall. Paying attention I can just place a little weight on the fuel pedal to keep it running no problem. It hasn't stalled once when I was paying attention to it possibly dropping, and seems to just be random... maybe 1/20 stops it doesnt want to idle. I have noticed that it doesnt matter if there are accessories (heater etc) on or not when it decides to do this. It's done it both when I had the radio, heater, seat heaters, headlights, and foglights on as well as when I don't have anything on at all (including no running lights as I have it set to not run the autos).

Etheraldreamer · Post by **Etheraldreamer** » 07 Oct 2011, 14:10

Last reply to myself, but just to reiterate, I had NONE of these symptoms before swapping the fuel pump... not that it HAS to be related, but it seems likely.

Etheraldreamer · Post by **Etheraldreamer** » 08 Oct 2011, 17:31

Post by **boosted5cyl** » 08 Oct 2011, 18:17

Might be an intermittant MAF signal. I know you said you just replace the fuel pump, but its quick and easy to isolate the MAF. Disconnect it while the motor is turned off, fire it up and drive it some.
Might be a good idea to check fuel pressure at the rail too.

Etheraldreamer · Post by **Etheraldreamer** » 12 Oct 2011, 13:26

What should I be looking for as I drive with the MAF disconnected? Lower milage? No stalls? What should I be paying attention to? Thanks for the help!

Post by **Ozark Lee** » 12 Oct 2011, 14:34

Is the check engine light on and have you read the codes? My daughter's S70 had similar symptoms and it was a flaky cam position sensor. It never did post a code for me but after I punted and took it into the local indy they got it to post the code. It hasn't quit since.

A bad MAF will usually cause the car to idle very poorly and just unplugging it will smooth the idle out since it goes into an open loop mode and makes decisions based on throttle position, RPM, and speed. It will kill your mileage and performance to run without the MAF but it is a good diagnostic tool. Unplugging the MAF will set a Check Engine Light but that is easily cleared.

...Lee

Etheraldreamer · Post by **Etheraldreamer** » 13 Oct 2011, 11:47

I should have noted that I have checked codes. All I have are the PCV system one which has been on the dash for 3 months or so... Plan to do it, but havent got around to it. You don't suppose the PCV system could cause such dramatic symptoms do you? I will remove the MAF and see what happens over the next couple days. I'll keep the code reader with me and try to take random readings and one right after it stalls (if it stalls again). Thanks for the guidance Lee.

Etheraldreamer · Post by **Etheraldreamer** » 14 Oct 2011, 11:56

On the plus side, replacing my faulty fuel pump and removing the rear drive shaft jumped my avg mpg on the commute to work from ~25 to ~27! Not too shabby