96 850 Turbo: Codes P0302 P1310 - problem ONLY during idle

Post by **misha** » 16 May 2022, 11:15

Remove negative battery cable for 10-15min in order to reset fuel trims and clear the codes.

Codes will not clear themselves after replacing parts....they should...but only after a few driving cycles....depending on what fault codes were stored.

If the codes come back....we will proceed further.

insession · Post by **insession** » 16 May 2022, 12:02

10/4 misha. Usually I clear the codes with my OBDC reader, but have just tried your method as well.

Post by **misha** » 16 May 2022, 13:37

Did you read this post:
http://volvospeed.com/vs_forum/topic/96 ... /#comments

insession · Post by **insession** » 16 May 2022, 14:15

I have now, thanks misha. So many possibilities!

insession · Post by **insession** » 16 May 2022, 16:34

One more observation: the engine, under the hood, looks a little shaky when in idle, but becomes static/stops moving once the rpm are 1500 or so and above..

Post by **abscate** » 17 May 2022, 01:16

That’s a textbook description of a missing cylinder. At higher revs the missing cylinder vibration matches another cylinder firing so you don’t feel it, speaking loosely

insession · Post by **insession** » 17 May 2022, 10:55

Thanks abscate - I take it the easiest to find out about that would be to disconnect one spark cable at a time and see which one may be the culprit?

Post by **misha** » 17 May 2022, 16:05

After reading volvospeed post...i would perform a compression test first.

If that ends up ok...then i would chase ignition and injection system problems.

insession · Post by **insession** » 28 May 2022, 20:04

Sorry guys, have been busy or lazy

Not gotten around to properly diagnosing this. Still same codes when idling in gear or crawling in gear

insession · Post by **insession** » 03 Jun 2022, 16:02

An embarrassing update

Pulled each plug wire to see if it would dramatically change idling. Found standing oil in #2 and #3, and both plugs loose. My bad entirely - last I regapped them, didn't have access to my wrenches, and borrowed a MOEN plastic plumbing deep socket that fit, and tightened it as much as possible. Clearly, not tight enough

Now that I did it on all plugs with the right tools, it idles less rough, though I'm still getting those two damn codes.
Wires sparked fine, and none of the pulled cylinders changed the idle in a way that would make one stand out over the others.