Replaced battery and now the engine runs rough

brice24 · Post by **brice24** » 11 Nov 2008, 17:23

I just replaced the battery in my 1999 S70 and now when I start the car it idles very rough and will not rev. What gives?

Mike-Halewai · Post by **Mike-Halewai** » 11 Nov 2008, 17:41

Call me crazy, but I would simply try a different battery first of all. If that has no effect, then you may need to test and try a few other things.

Are you sure that you are using a large enough, or small enough battery, etc?

Post by **BEJinFbk** » 11 Nov 2008, 18:06

What is the voltage measured at the battery?
Check when off, and also when running.
( Is this a new battery? Just Checkin'...)

895meztz94 · Post by **895meztz94** » 11 Nov 2008, 18:14

When I replaced my battery I started having what I think are ETM problems.

waynej · Post by **waynej** » 11 Nov 2008, 22:39

Did you have the key all the way off when disconnecting the battery? If not you can fry some expensive electronics. Did you clean the cable ends before connecting the new battery?

bobsnow100 · Post by **bobsnow100** » 12 Nov 2008, 14:08

What are the condition of the battery cables and any other wires that connect at the battery. Make sure they are good . Sometimes the copper wires get white oxidation on them and you get bad contact. Check the ground wires also.

brice24 · Post by **brice24** » 15 Nov 2008, 05:32

OK. Battery good. I borrowed a OBDII scanner and found no codes except that the O2 sensor was not reading any voltage. I unpluged the O2 and now the engine will idle but not rev. What next?

Post by **MadeInJapan** » 15 Nov 2008, 05:42

Are you saying the wires to the 02 don't show voltage?
If so, you're going to have to fault trace those wires to where they connect in the engine bay and if that connection is corroded clean it, etc. I'm not sure what the voltage is suppose to be on those wires, but seems that Lee posted about this some time ago. If you're saying there is no voltage out of the 02 itself, I believe this is normal- it should show some resistence though, but minimal.

Post by **mom** » 19 Nov 2008, 19:25

Everytime you disconnect the battery, the computer resets itself and it has to relearn your engine behavior particularly on idle because it is the reason of being of the throttle body. It will run smoother after a few hours.