Intermittent stumbling 2005 xc70 resolved, a Fuel pressure regulator) Topic is solved

Post by **abscate** » 03 Apr 2016, 06:04

I missed this before. You do have symptoms of an electrical failure like a bad battery cell or cable. When voltage fluctuates on these cars ( really any car today) Hades breaks loose.

I bet your battery improves the situation. Don't be annoyed, you are still about 2000 ahead in diagnostic costs!

Post by **vtl** » 03 Apr 2016, 06:22

abscate wrote:I missed this before. You do have symptoms of an electrical failure like a bad battery cell or cable. When voltage fluctuates on these cars ( really any car today) Hades breaks loose.

Usually car says "low battery voltage" long before battery becomes a real problem. Or even "electric system failure" if alternator failed completely.

Which voltage exactly fluctuates? With DiCE/VIDA every module can show voltage supplied.

Post by **abscate** » 03 Apr 2016, 08:22

I think this an intermittent loss of 12 VDC which is killing this car.

Post by **chrism** » 03 Apr 2016, 14:11

The stumbling under acceleration, going up hill, and when turning hard right, are the exact symptoms my wife had with her 2005 2.5T S80. Turned out to be the fuel pressure sensor. Certain VIN numbers have a recall on that sensor where Volvo will foot the bill for one free replacement. In our case it took forever for the CEL to come on. Connecting a fuel pressure gauge to the injector rail and monitoring it under actual driving conditions confirmed it was a fuel issue - pressure fluctuated in sync with the stumbling.

amy in md · Post by **amy in md** » 06 Apr 2016, 09:37

I already opened up the alarm siren and replaced the battery. Figured one from AZ wouldn't have the water damage that mine has. Instument cluster only went when the car nearly stalled and hasn't had an issue since. Supposed to be cold again this weekend. I would really like to get the ECM out and see what the connectors look like. Thanks.

Post by **vtl** » 06 Apr 2016, 11:20

It's electrolyte, not water in alarm siren.

amy in md · Post by **amy in md** » 07 Jun 2016, 13:59

Ended up being the fuel pressure sensor. No code ever came up. It was in stock at a location near me and took five minutes to replace the next morning. Thanks all for the help.

Post by **mrbrian200** » 05 Jul 2016, 14:13

I'm going to key in here. Your (drivability) symptoms are remarkably similar to the troubles on my S60 that threw me for a loop. Though I had more than one issue, the main culprit was a failing electronic throttle assembly. Cleaning it would be of no use, internal gears are made of nylon and as they wear they like to bind/stick (occasionally, not all the time) at throttle plate positions roughly 15 and 25% that corresponds to the first few teeth on those gears in the part throttle range that get the most wear. To check you have to have the engine running connected to your OBD tool or VIDA that shows actual throttle plate position. Perform slow ramps up to 3000RPM then back off the throttle slowly. At idle the throttle plate position should rest somewhere in the neighborhood of 6-10% If you see it "stick" those higher positions bingo: The ETA is your problem. With the engine off the gears tend not to ever bind/stick. Must perform test engine running. If you hard/fast kick the throttle while experiencing symptoms and they go away that's another indicator.

amy in md · Post by **amy in md** » 05 Jul 2016, 20:13

So far it seems the fuel pressure sensor was the culprit, but I'll check this out when I get home. Thanks.

Post by **abscate** » 06 Jul 2016, 03:27

Thanks for the final report, Amy. Those help. I was way off on this one.

Can you post the part number you replaced if you have the receipt handy please?