S70 base model. 1998. 107K miles. Automatic.

A bit of background: my daily commute involves a quick jaunt onto the freeway and a hill climb. Problems started back in May. At one moment with alarming regularity near the same highway marker each day, the car would suddenly shudder once or twice at first, for as long as 30 seconds afterwords. Not just a small shudder. But, a torque-converter is locked lets misfire the engine a few times see if they spill their coffee kind of shudder. Check eng light would flash while this was happening, sometimes the up arrow light. But, no saved codes. Then, the car runs fine until I stop, cools down, then drive again.


Shotgunned the fuel pump controller relay thing. Not much of a difference. Tried flushing the trans. Good idea but no difference.

Dealer couldn't reproduce the problem.

By now, if I am on a resi road, about the same amount of time, engine would just die. But, car would restart right away.


Bought one of the ODBII readers that took real-time recordings of up to 20 blocks of data.

Ok, O2 sensor 2 after the cat is flatlined 0v. That can't be it. O2 sensor 1, about 0.5v or something like that. Recorded a session on my daily commute. Manual trigger record as I approach the same mile marker. Got it.

When I plugged it into my PC to see the graphs, during an event, O2 sensor 1 would flatline but recover.

Today, replace O2 sensor 1. Problem solved. I'll replace O2 sensor 2 when I can recover from paying $300 for #1 plus $200 for the reader, $50 for the labor, you know the drill.

Or, I could get new brake pads next time.

I asked the volvo mechanic why they didn't tell me O2 sensor 2 was dead. "Oh, those are about $400 installed and they don't really do much..."

Sigh. He may be onto something.