Revving Woes

Lads,

I have searched through keywords like surging, revving, one cylinder, etc and found some good info, but posting this issue cause I like the interaction.

Yesterday, leaving work I cranked the SD and it backfired through the TB’s, then started right up and ran normally. Made it about 10mi through lights and stops. Was decelerating for a stop, clutched it, and it died. No biggie…happens. Torched it off and it was revving up to 3k down to 1k, up to 3k down 1k, over and over ad nauseum. Had to get home so I dumped the clutch and kept it between 2-3k. It would run there, but was lacking. Over 3k it felt\sounded like it was picking up a cylinder. Had to kill\restart it several times at lights. Always doing the revving on restart.

I’m leaning toward coil pack. It has been running a little rich lately, though. Maybe a shanked plug?

Battery is good. BGC was cleaned\greased months ago. Have been riding in 30-80F weather, daily.

If it were an IL4, one dead cyl would be slight, but shouldn’t the twin be wicked noticeable? Never had a twin before. Well, the Pasternack sisters, but that’s a different story.

Thanks much,

Rob

2008 990SD, 11k, Rottweiler intake, LV exhaust, SAS kit, PClll, G2 tamer

Had similar symptoms = failing/failed coil pack, usually rear for some reason = running on one cylinder - 'grab' front and rear headers to see if they're hot..........

Thanks!

Got'em ordered. Get to it this weekend.

Hey,

Got sidetracked by life for a few.

I picked up two coil packs from a wrecked SD with less than 5k on it. $22, figured I couldn't go wrong. I'd rather look lame than have the wrong info in here. Wasn't the coil. I noticed right away once I finally looked at it.
The backfire had blown the rear TB out of the intake boot. Whenever I was cranking the throttle it would lift it just enough to suck a butt-ton of air. Easy fix. Glad of it.

All sorted.

Thanks,

Rob

Comrade Rob: It's nice to see some feedback on the ultimate cause. I'm sure that someday, somebody will have exactly the same problem and your feedback will save a lot of stuffing about.