850 T5- 1997- rough idle, slow off the line

jallert · Post by **jallert** » 05 Mar 2009, 11:51

Don't know if these are related, but when my 850 T5 is in drive it idles roughly. When I move it to park or neutral- it fine. Also seems much more slugglish off the line (turbo lag?). I have replaced all plugs, points, and rotor recently. Wires are not very old. Thanks.

Post by **MadeInJapan** » 05 Mar 2009, 16:29

John, I would suspect the engine mounts- especially the one in the circular arm above the engine on the driver's side- it's called the torque mount. Mine was replaced with a polyurethane mount in that location on my S70 and I get vibrations too. I'm thinking of switching back to a rubber mount- they are cheap from www.fcpgroton.com Let us know what you find w/ your engine mount. If not there, you'll have to look in a couple of other locations for other mounts- FCPG has diagrams of all of these and we'll guide you through their replacements if they're bad.

jallert · Post by **jallert** » 23 Mar 2009, 10:15

Thanks for the idea. I just replaced the upper engine mount as it was in two pieces with polyurethane. Didn't notice any change in idle afterward. Why would a mount affect idle? does that affect slow off the line too? It seems more like a fire/air/fuel problem, but just guessing. Thanks for the reply.
John

Post by **MadeInJapan** » 23 Mar 2009, 22:08

Never mentioned "slow off the line." That's another issue and definitely could be your air/fuel mixture or something else. I have now swapped back to the rubber torque arm mount and my vibrations in my S70 are noticeably better.

Paul240480 · Post by **Paul240480** » 24 Mar 2009, 13:41

Having had very similar with my 480 Turbo auto, I'd suspect the following:
Air leak on turbo intake pipes. In early stages, idle can be okay, but the leak will be more profound when you 'boot it' causing a lack of power. In later stages it can affect idle too as in like you say, neutral it's okay, but hook it into drive an idle goes all to pot.

Idle control valve (guessing you have one?

). Can be cleaned, take it off & soak it in parafin overnight?

Injector seals leaking? May not be relevant on 850s? I'm still learning, but thought it worth a 'mench'.

Blocked PCV.

Good luck & do let us know how you get on, I'm new to diy on 850's so very interested in what ever you find