1998 V70R - brief stumble during acceleration, blinking CEL, P0116 and P0302

[atomicthumbs]

Howdy. I recently drove my V70R again after a while of not driving it anywhere significant. Recently it's developed a fuel tank venting issue which makes it difficult to fill, and other people in my family drove it without filling it due to that.

Today, I took it out to get gas, as it was very low (20 miles til empty according to the gauge). At this point, it was nearly completely warmed up according to the temperature gauge. I drove it out of town onto the main road, floored it, and it pulled to 50 mph, where it hesitated, and the CEL started blinking, then stayed on after ~20s. I drove it very gently back the way I came.

OBD2 reader says it threw P0116 (engine coolant temperature measuring problem) and P0302 (cylinder 2 misfire) codes.

My semi-educated diagnosis is that the ECT sensor failed, and the engine misfired when the ECU figured that out and switched to precomputed temperature values. How likely is this to be true?

[erikv11]

Clear the codes and make sure the p0302 doesn't come back. If that is the case then you are probably right that there is an issue with the ECT or its connector. That is assuming all of this happened after getting gas, that part is unclear to me.

About the fill-up issue, read the second half of this post https://www.matthewsvolvosite.com/forums ... 6&start=14. And don't let anyone drive it who won't keep it filled, that is a sure way to ruin the fuel pump which is a bear of a job to replace on a 98 R.

[atomicthumbs]

The car still has very little gas in it (as the station is 5 miles away and I didn't want to risk driving it with the CEL blinking at me). I'm going out today with a can to get a few gallons for it.

Edit: Is there any test mode that cycles all the valves and so on, like there is with the OBD1 cars?

[erikv11]

If the tank is that low then all bets are off on the stumble and codes. It could have just been running out of gas, that would easily explain the P0302 but not the P0116 but who knows. I would get some fuel in it, reset the codes, then start watching to see if anything happens again.

[atomicthumbs]

Added $10 worth of gas. No issues during a short drive, but it remains to be seen if they're gone forever. Now the question is: which engineer did they have to check out of the insane asylum to design the fuel system on this thing?

Edit:



I feel like I'm looking at some kind of horror from outside space.

Seriously, "expansion tank"? "Pressure sensor"? What in God's name, Volvo?

[scot850]

Hey, this is easy, try a 2000 R! Been there and done that. If you are having problems fill the tank, it could be the roll-over sensor is bad. If I read Vida right, it is attached to the fuel filter bracket at the rear of the car. Pain to get to. These can fail and prevent the tank venting when you are filling the car. The only place for air to escape as fuel goes in is back up the filler tube.

Neil.

[abscate]

These are the guys you can thank for still be able to live in many parts of CA. EVAP emissions were the cause of smog in the 70s which was horrific. Volvo is no more complicated than most other makes..you have to both purge the vapors and be able to test the system.

Keeping this 17 year old car out of the junkyard is the best thing you are doing for the environment, though. It's very unlikely you are putting vapors into the air, it's much more likely the testing circuit has failed