Rough beginnings

james321 · Post by **james321** » 29 Jan 2017, 15:15

Hello. 2000 V70 2.4 L 5-cylinder non-turbo.
It started with the cold weather, but now even when warmer it's still doing it.

When I start up in the morning it would run rough for about 10-20 seconds. Now, over time that's stretched out to about 4-5 minutes. After that, it smooths out and idles at normal idle 850 rpms. If I park it for a few hours I'm back to square one. If I try to pull away before it warms up there is no power. It feels a little like it's missing, or clogged.
After it smooths out now, I can hear an occasional miss while sitting at a red light. I had the throttle body replaced from Xemodex in July.
Clogged fuel injector? Bad plug? Sounds like maybe, but it eventually smooths out and runs fine.
Not sure what fuel injector cleaner I should try if that's one route I should go.

ps. I can't be sure, it could be my imagination it's so faint, but I thought I smelled gas at a stop light when the heater was blowing.

Thanks in advance.
Jim

Post by **FlyingVolvo** » 29 Jan 2017, 15:32

Any check engine lights? If so, get a code reader and post what you find (some auto stores will check for free).

My bet is on a bad engine coolant temperature sensor. When those go bad, they give the computer bad info on the coolant temp leading to incorrect fuel/air mix. It sounds like once your car is warmed up, it settles down. Do you know if it was ever replaced? Make sure to only use the genuine Volvo part for this sensor, no aftermarkets.

When you say it runs rough, are the RPMs higher or lower than normal? Bouncing up and down like crazy? I don't think I'd suspect a bad plug unless there's a real misfire going on. When was the last time the plugs were changed/gapped?

james321 · Post by **james321** » 30 Jan 2017, 09:33

RPMS run higher just a bit. 950 to 1000. Not bouncing up and down.
Bought it in June so I don't know when the plugs were done.
Replacing the coolant temperature sensor seems like the best place to start.
Thanks.

ps. Could a bad o2 sensor produce these symptoms?

Post by **FlyingVolvo** » 30 Jan 2017, 11:18

A bad front O2 sensor could definitely cause issues as well, but will usually produce very poor MPG and a code.

No check engine light on? (Make sure the light isn't burned out by looking for it when you go to accessory position on ignition).

Post by **rguzz** » 30 Jan 2017, 18:15

Make sure the integrity of the harness to CTS is good as well...take apart the connectors and check to see that they haven't rotted away inside creating a poor contact. If so, replace the connector and internals, these are OEM Volvo still.

Post by **JRL** » 31 Jan 2017, 09:45

james321 wrote:RPMS run higher just a bit. 950 to 1000. Not bouncing up and down.

Non turbos idle a bit lower

james321 · Post by **james321** » 31 Jan 2017, 13:20

No check engine light on? Yes. My o2 sensor I know is showing up on the codes. Check engine light has been on and I know I need to change the o2. The mpg is affected, yes.
Now, since THIS issue has been going on (rough idle for first 4-5 minutes) the check engine light blinks.
Then when it smooths out to 850 RPMs , the check engine light is steady on, (like it has been since the o2 went,) and it runs fine.

Post by **FlyingVolvo** » 31 Jan 2017, 15:24

Ok, now we're getting somewhere! As I understand it, the blinking CEL does indicate a misfire. I would definitely change the O2 sensor first, because you know it's bad (make sure to use the OEM Bosch one that is plug and play). Check to the codes again to see if it indicates which cylinder is misfiring. Instead of guessing what's wrong, we could have something more solid to go after.

We'll get there! Always a fun troubleshooting process with these cars.

james321 · Post by **james321** » 02 Feb 2017, 10:29

Thanks!

Post by **abscate** » 02 Feb 2017, 13:23

Many OXS codes won't be fixed by replacing the OXS sensor. The only ones that will for certain are the heater failure codes.