2008 XB12XT Poor Idle & Backfire

[My91Ranger]

Hey Guys, fairly new to the site, love all the great info, but haven't been able to find a solution to my issue.

I have a 2008 Xb12Xt with 20,000 miles on it. I bought it back in February and it ran and idled well. I put in a new set of Iridium plugs and started having problems with the bike not idling and stalling at lights. Re-installed the old plugs with the same results. I have since put in another set of plugs and some new wires (one had a nick in the insulation).

The main issue I have is the bike doesn't like to idle when cold. I will have to start the bike 2 to 5 time to get it to stay running, and will stall out at the first light or two I stop at. The bike also backfires/misses through the intake occasionally when cold and trying to idle. Once the bike has been rode for a few miles it will idle fine and always pulls through the RPM's well.

The check engine light has not come on, and I have pulled the codes, but nothing comes up. I have tried cleaning the IAC and throttle body, and have done the breather re-route. Not sure what else to try and what's causing it. Have also reset the computer and done the 'learn' ride a few times, but it has never helped.

Appreciate any help!

 

[buellbradski]

What plugs ?
Did you do a tps reset?

 

[oisterska]

Sounds exactly like my issues with my 2009 XT. Cold starts were a bitch (sometimes even warm starts). Wandering idle on startup, intially took two or three tries to get it going, then it would sometimes die and still take another few starts. Took it to harley and they threw parts at it but nothing seemed to help (fuel pump, oil pump, pistons, cylinders, iat, etc. thank god for manufacturers warranty).

Finally I noticed that there was a crack on the ecm where the connectors hit the ecm body. The seat was rubbing on the connectors and it was causing a crack in the ecm exposing the sensitive bits inside to moisture etc. They replaced this (again, thank goodness for warranties - this time extended service warranty) and she is right as rain. I got a hawk exhaust and EBR ecm and did the ECM relocation as suggested by many threads on badweb. Just shove the ecm in front of the battery. I padded it with some velcro tape to reduce vibrations.

Below are videos of my starting issues. Note the wandering idle and the multiple start attempts especially in the first video. This would be followed by me nearly dumping it pulling out from a light into a left turn when the bike almost stalled out, all on more than one occasion.

 

[djohnk]

Ha, what a coincedence! See what I just posted on another thread here: bad ecm post

 

[My91Ranger]

Thanks for the replies!

The plugs are DCPR9EIX NGK Iridiums and yes i've done the TPS reset 3 times.

I checked my ECM and sure enough its cracked all the way across the connector! You guys nailed it, and i've very excited to finally know whats wrong. Is there a link to the ECM relocation? Did a search and didn't come up with anything.

Also any good sources for a new computer? I saw the EBR ecm for sale fore 305, but I have a stock exhaust and don't plan on changing it any time soon, so a stock ECM would be fine.

 

[oisterska]

See below for a lot of information regarding the ecm relocation. Disclaimer: it goes to the other buell site. If there was a writeup on here I'd have linked to it instead... and I forgot to take pics of my relocation so no write-up from me.

Link

Really, it's just a matter of taking it out of the stock location and shoving it in front of the battery. Once you get in there it's pretty self explanatory. Others built tabs/brackets so it could still be solid mounted. Good luck!

Oh, and even if your ECM is stock, look at the EBR ecm for stock exhaust. I have heard it does wonders for stock exhausts.

ebr

 

[djohnk]

I wedged my ecm between my battery and the fuse box ... there is just enough space there for it (make sure you push it all the way down). For a long time I just unbolted it and laid it loose in there, didn't cause any problems. If you relocate it, just taking the stress off might be enough to get you by until you find a replacement.

 

[stevengeorgia]

I'll have to check mine(ecm), It would be a good candidate for the motion pro nitro tape if it is, I love that stuff...Mine has been missing badly too...The stock-type plugs that were in it were shot, So I'm going with the ngk dcpr9eix plugs, Mine's also got a twin tec control module on it, Haven't messed with that yet, A friend is a harley/buell mechanic and was supposed to get back with me on that...I know one thing, This bike hauls ass in the upper revs, It must be on the WOT setting(Wide open throttle)! lol cool bike, I ordered some rox isolator "2 risers for it(7/8)...For like $85, A lot better than the $163 on their website...Oh, And while the k&n filter is a good upgrade, It's notable that they sometimes allow too much air, Allowing the stock type plugs to wear faster, Hence the main reason I'm going with the iridium plugs...(The plug installation is a little bit of a pain, Not Sooo bad, But...)

 

[My91Ranger]

Thanks for all the help guys. My new EBR ECM came in the other day and I got it installed and relocated out of the way. Bike starts up first time every time now, and no more popping or missing. Very impressed with how much smoother the EBR computer is. No more lugging under 2k RPM's and a lot smoother while cruising. Still waiting to see if the mileage improves any, but so far it is a nice improvement.

 

[steve92106]

Looked at my ECM (again) yesterday and couldn't see anything wrong with it but having some of the same issues (see the other post). What struck me was it looks like my brain box is already positioned forward of the battery and there's a hard rubber guard attached to a bracket on the seat pan, just a rectangular block really, to prevent the seat from rubbing the ECM itself. From the other posters is sounds as though you don't have this. You can see an imprint on the underside of the seat shell (I have the tall saddle) where this block is making contact. I seriously doubt the ECM itself is getting any pressure from the seat. My bike's also an '09 but maybe they had a fix in later in the year?

How does one read the codes? I hate to rely on the dealership. I had them do an oil change a few months ago and checked the level after a couple of rides and it was almost off the bottom of the dipstick! No measurable consumption since then so I suspect the tech was sabotaging my bike to generate business. Either that or he just forgot to fill it and either way I don't trust him.

 

[steve92106]

I went out for another look and to do the TPS reset just now. When I looked really hard at the ECM I noticed very fine cracks in the rubber case at juncture with the forwardmost of the two multiplex connectors. It looks as though maybe the seat has been putting pressure on the connector itself and the hard rubber casing material has fatigued. When I pushed down on the connector I saw the cracks widen a bit. Could this be causing my problems? The bike runs fine until I get it home from a long (150-200 mile) ride then the idle goes to crap and the CEL illuminates. Would applying some silicone sealant over the cracked rubber be a good idea?

 

[BuellyBagger]

@steve: I suggest getting the bike warmed up and do a little "wiggle" testing while its idling. Give the connector on the ECM a good shake and tug (don't try to rip them out or break them just try to move em). If your CEL comes on when u begin the wiggle test (or ur idle goes to crap) you may have just found your issue. I had an ECM go bad in my ULY a year ago with no warning and no apparent damage. It thru TPS trouble code which I promptly shot from the hip and replaced (to no avail) and then I got a service manual and actually went thru the steps of diagnosing it. Came down to the ECM. So I got an EBR one (set up for my exhaust) and so far for 1.2 riding seasons, she's all good (knock on wood)

 

[steve92106]

Buelly, Many thanks for the suggestion. I'll take a stab at that. Even if it doesn't confirm a problem, I think I'm going to cut away some of the seat shell and make sure it can't put any more pressure on the part. I think I'll also use the sealant. Even if it's not the source of the problem, it can't be good to have those cracks.

 

[steve92106]

Post Mortem: After not getting any reaction to BuellyBagger's wiggle test, I did seal up the ECM and ride the bike again. Again, after a short (100 mile) ride the idle started doing it's possessed by demons thing. So, regretfully, I took it into the HD dealer for a diagnostic and was told yesterday the immediate culprit is the "idle air motor". I have no idea what that is but it's an estimated $315 fix which seems like a bargain considering what I was afraid of hearing. The tech also recommended replacing the ECM since the the harness can be moved when the plugs are wiggled. I figured since the problem only occurs at idle and since there were no error codes indicating a bad ECM, I would just wait. The factory ECM is over $500 before the cost of a new download! It may come to that but I don't see any sense in dropping that kind of money until it's confirmed. The EBR ECM isn't legal in CA and they've been getting pretty sticky about that. Only good thing about waiting for the part is I get to rent a Fat Bob for cheap and I've been wanting to test ride one for months.

 

[steve92106]

Next Chapter in My Little Saga: After paying for the idle air motor plus another $95 for the diagnosis (I always thought a diagnostic charge came off the repair bill, what happened there?) I rode it to work on Thursday. On the way home I "diverted" to a little twisty back road and was just exiting to the freeway interchange twenty minutes later when the CEL light came back on. Now the dealer has it again. I guess they've had a number of conversations with HD with no brilliant ideas to date. It's probably a good thing I don't have the money to buy another bike.

 

[steve92106]

Well, almost $1100 later the shop claims it's solved the problem with a new ECU.