sudden intermittent and random stalling 1999 s70 manual

[amblerman]

Hi folks

1999 s70 5 speed.
in early May, when we had weather in the 70s, I was driving around with windows down thinking "Man.. this car still really rides and drives nice!"

Famous last words.

I found myself approaching a light, I pulled car out of gear, came to a stop and before the light changed, I saw lights on my dash.
Car had stalled out. Started right back up.

Car continued to drive fine.. and then as I was approaching another light, I put in clutch , pulled it out gear and coasted. When I pulled the car out of gear, the RPMs dropped to 0.

It doesn't happen all the time. But it does happen. And when it does stall out it seems like the RPMs drop like a rock. Like 3000 RPMs, take car out of gear, RPMs drop suddenly. I have not tested how fast the RPMs drop when it stalls vs when it runs fine so I might be wrong about this.

Other symptoms seem to be occasional :
1) RPMs jump up and down 1000-1500 range in rapid change. But depressing pedal increase RPMs and makes it become stable

2) I have seen the idle drop to about 500 and then eventually move back up to 800ish but rarely. Note my car already has a XeMODeX ETM in it. I am second owner of car and it came to me with a XeMODeX serviced/updated ETM. Do the XeMODeX updated units go bad with regularity?


3) I have noticed that the pedal feels dead at times. This surprises me because when I notice this, I am not actively trying to depress pedal. There have been times where I am driving at a constant speed (around 25) when I feel like the pedal feels dead. It's odd because I never even noticed the pedal had a feeling at all. Just all of a sudden it feels like it's vanished. When this has happened it seems to "come back" withing a couple of seconds. When this happens, the engine RPMs do not change. It's just as if the pedal seems to vanish. I don't know how to properly describe it. Imagine if the pedal was designed to provide mild haptic feedback and then all of a sudden it doesn't.

What I have checked
I just started diagnosing this.
I was hoping there was some leak in the intake system or something similar. I started up the engine (it always starts fine) and then sprayed various components with starter fluid. No change in engine RPMs.

That's it.


The car worked all winter long just fine. No hiccups. It was only after I commented on how nice it was driving.

Can anyone suggest a debugging plan here? What to test and eliminate?
I also do not seem to have any active codes
-A

[scot850]

Xemodex units can go bad, but unfortunately the lifetime warranty does not transfer to you. So unless you know the original owner and can contact him to help facilitate returning the unit you are on you own.

Having said that, you may want to check your fuel pressure is good and you have a system that holds pressure when you switch off for 20 minutes or so. You should be getting over 50psi when running and even if it drops a little below that should be good. However, if you lose pressure immediately after switching off it could be the check valve is failing.

My brother has been fighting a running issue on his 850 which still eludes him, but that is a different beast.

I would suggest the ETM is the most likely culprit.

Neil.

[abscate]

Definitely check fuel pressure and see if fuel delivery is up to snuff.

It does sound like the ETM though, if you have a higher end reader it will pick up pending codes the cheap ones won’t.

The good news is that if your s70 is non-turbo the ETM swap is simple 15 minute swap. Leave the old ETM in car until you test the new one since the wiring harness is captive behind the starter.

MVS has a special loaner test ETM program between stony Brook and Penn , reach out for details. That karma you bought donating that 1998 v70 to Beryls Volvos has blossomed and bears fruit. Catch me this week before I head off the China, whom we call Red China, to look at nuclear bombs, which we call, a device.

Definitive test fir ETM is sweep test in Vida of course.

[abscate]

Dispatched test ETM from Shagg to Amblerman, stay tuned. It was very satisfying to walk to the shed, and pull down the box labeled UBG ETM Shagg 1999 v70 NA off the shelf