I have a 99 S80. It is a 2.9l non turbo. I have had a used trany dropped in. It ran fine for a while. Shifts fine not noticing any sliping. Recently my MPG has been dropping. Every other time i turn on the car the computer MPG drops a couple tenths of MPG. For instance 26.6 then 26.4 then 26.2 and so on. I took it to the dealer and they said my fuelpump was bad. I also needed a timing belt. Ok so i put i new pump in myself and did the timing belt. first mistake i did them at the same time. Probably dumd but its spilt milk now. I put everything back together and it fired up. I let it run a little and then took it for a test drive. Seemed fine. Filled up with gas and took it home. Went to work the next morning, evrything seemed fine. I ran an errand later in the day and the car started running ruff at low idle. Got back to work and the engine died. tried to restart and it would run very ruff at 700 rpm and then stall. I tried to let it run thinking I had air in my gass line or dirt from the fuelpump change. The rpm would fluctuate between 800 and 500. I shut it down thinking I would have to have it towed. After work I started it and it started right up and ran smooth. I drove home no problem like normal. When it was running very ruff the drive slow service urgent message came on as well as the emissions service requiered. a friend suggested unhooking battery to reboot the computer. I did that and now the car will not start. It cranks, starts goes to 1000rpm then drops to 500rpm and stalls. What the hell is going on?????? I thought maybe my timing had jumped a tooth but then when it drove me home after work I didn't think that was likely. I drove it a total of 50 miles including test drive and run to work and home. When I took it to the dealer i was suspicious of the throtle body or MAF. I feel like the car is not getting air or something along those lines. I thought maybe that was why my MPG was dropping. I hope someone can help me. I have always been amazed at the wealth of knowledge here, and am very thankfull for all the times this forum has saved my butt. Thank you in advance for your time and any help you can give. Desperate, Ron Z

 

Is the fuel pump and sending units lined up correctly like they are supposed to be?
There is arrows on the units that are supposed to line up with marks on the tank.

Also on the drivers side sending unit did you clip the line back to the sending unit when you installed the unit?

It might also be a throttle body issue have you had the recall software downloaded yet?

 

Yes the throtle body software is up to date. i put the fuel pump back together exactleyh as i took it apart. And it ran like a champ for a short time. I assume it would not have if the lines where switched. If you can think of any info I did not include please let me know.

 

Do you remember cliping the lines on the drivers side setup? The line and valve looking thing clips onto the bottom of the sending unit.

Is the tank full or close to empty?

I am thinking maybe the drivers side part isn't connected and is sucking to the tank causing problems. I could be wrong just a guess.
Also it would be a good idea to get the codes pulled.

 

thank you Tech. It was a problem with how I had put it back together. It is running now but havn,t taken it for a test drive yet.

 

OK I hope that fixes it.