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Old 10-25-2012, 12:08 PM   #1
BigTony OP
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990 stumbling after major maintenance - troubleshooting w/ TuneECU

2007 990 Adventure here...So I'm just reassembling the bike after a major maintenance (valves, plugs, fuel filters, wp shaft/bearings, heat insulation on tanks and airbox, dual fan kit, ceramic coated head pipes,etc). This is the first time I've done the maintenance myself (13k miles now - had it done by a reputable shop at 9K miles but didn't think they did a good enough job).

I just put the left tank on last weekend and fired it up briefly to bleed the coolant and do some checks. The TPS was reading about 0.61V warm, so I dialed that down to 0.58V warm and sync'd the TBs using TuneECU so that the hPa readings match at idle

I reset the ECU but didn't let it idle for a full 15 min yet. On the center stand with engine running and small throttle openings the bike RPM is surging a bit. Checking with tuneecu running and with small throttle openings I see the map pressure reading dip on the back cylinder as the bike starts to stumble. The rear cylinder seems to have a lower pressure reading in general except at idle where I set it to match the front via the screw on the throttle linkage.

Now a couple of other random notes, when I did the valve shims I noticed some heavy varnish/dirt/gunk buildup in the intake manifold. It took a lot of elbow grease but I cleaned it out of the intake. However, unavoidably some of that varnish washed down into the engine with the tb cleaner, etc.

I also had the header pipes ceramic coated.

I have been getting a faint smoke/vapor from the exhaust if I rev it a bit. Also the exhaust smells a little weird. So I don't know if this is due to the ceramic coating, the varnish burning off, or something else entirely, but is something I'm keeping an eye on.

So I haven't done much other than to fire the bike up and see how it's going. I'm wondering if there are other checks folks would recommend that I could do with TuneECU/other to check things before taking the bike out and running it? I'm a little nervous with all the work I did to it, but it starts right up. It's never run smoothly per se but shouldn't be surging and stumbling so I'm wondering if there are any ways to diagnose that. Or is it possible it'll

(I've got open leo vince w/ akra map on there right now ie O2s are off, but may switch back to stock map and spark arrestors shortly)

Any suggestions?
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Old 10-26-2012, 09:14 AM   #2
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Maybe you should make sure no leaks from the throttle bodies?

Air leaks mess with A/F mixture and create all sorts of problems...
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Old 10-26-2012, 10:35 AM   #3
BigTony OP
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Is there a good way to check for air leaks? Like I heard in the old days on cars you could spray wd-40 around a vacuum hose and see if idle changed...
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Old 10-30-2012, 12:33 AM   #4
two trackin fool
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I dont own one YET but are you sure you have all you plugs plugged in completely ?

MAF , IAT , ECT one of these sensors missing will give your ECM fits !
Stay Patient and Trust your Journey
'10 990 in White
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Old 10-30-2012, 09:35 AM   #5
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Did you have to do much adjustment to synch the throttle bodies? I would swap over the sensors, see if a difference occurs, indicating an inaccurate sensor.
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Old 10-30-2012, 11:46 AM   #6
BigTony OP
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I got the bike fully assembled, put in my spark arrestors and went with the stock fuel map, so I can compare to before the work. Its actually running pretty well overall (better than before the work), but I still think the rear cylinder is weak. At idle I'll occasionally hear the rpm blip up and there's kind of a 'chuffing' sound in the left exhaust pipe. Just sounds like it's not hitting right compared to the other side (I'll have to check for exhaust leaks too). I also get a higher RPM vibe through the whole bike.

Good idea about switching the sensors around. I was going to fiddle with the TB balance some more so I'll see if it's possible to switch the sensors w/o removing the tanks
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Old 10-30-2012, 06:05 PM   #7
BigTony OP
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Hey so I fiddled with the TB balance a bit - doesn't seem to fix this issue with the back cylinder seeming to sputter, based on the exhaust sound.

Anyway, just wanted to see if anyone sees anything amiss in the TuneECU screenshot. Like I notice the 'Injector Pulse' is pretty different left to right but don't know if that is abnormal.


BigTony screwed with this post 10-30-2012 at 07:18 PM
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