"popping" on downhill / relaxed throttle

Edwub · Post by **Edwub** » Fri Apr 20, 2012 12:03 am

Anytime I let go of the gas and start to coast down a hill, or coast to a stop towards a traffic light, my Blur pops. It sounds like I've been feeding it minature beans, cause there's a little toot from the backside. It really only happens when I'm coasting. I can force it, if I give a slight little twist during mid-coast.

Popping indicates that it's running "rich" right? It's a little too much gas, that basically ignites later?

Is there something I should do, or be concerned about?

It's a Blur, so it's fuel injector. I've been running 89 gas for a while (see Blur forum discussions), but I experienced the same pops when I was in 87. I'm about 5 miles from the beach, and the weather is between 50 to 80 degrees about 90% of the year.

I wonder whether this effects my performance and mpg. It doesn't *always* happen, but it does. I wish I had documented when I get more/less of it. I'm due for oil & service next month - had my first service done on time.

Raiderfn311 · Post by **Raiderfn311** » Fri Apr 20, 2012 1:04 am

Yeah, first indications would be its running rich. Seems like the FI would take care of that, right?

easy · Post by **easy** » Fri Apr 20, 2012 1:16 am

sounds like exhaust leak

NathanielSalzman · Post by **NathanielSalzman** » Fri Apr 20, 2012 5:52 pm

There are a couple of different kinds of exhaust pops. There's what's often called back-burble, which is when there's a bit of extra unburned fuel igniting in the exhaust. Then there's sharper popping that actually comes from the engine actually being too lean. If you rev the engine, then let off the throttle real quick, and it takes a noticeably long time for the RPMs to drop, then you've likely got a lean mixture. Either scenario is unlikely with EFI, but only if the system is working properly. The best way to tell is to pull the spark plug and see if it is either white (lean) or sooty (rich).

Your O2 sensor could be malfunctioning or your EFI computer module might be faulty or need to be reset. You might also have partially clogged injector. An easy way to reset the module would be to disconnect your battery for 30 minutes, then start the scooter back up. The computer will have to take fresh O2 readings and that just might do the trick.

It might also be the case that a richer off-throttle mixture is programmed into the EFI map simply because some people like the sound of the back burble. They do that on the MINI Cooper S, for example.

Either way, on an EFI engine, it's important to keep track of your gas mileage, as big swings either better or worse can be early symptoms of fuel system problems.

Good luck!

Dooglas · Post by **Dooglas** » Fri Apr 20, 2012 6:04 pm

easy wrote:sounds like exhaust leak

This would be my first suspicion as well.

Edwub · Post by **Edwub** » Sun Apr 22, 2012 2:15 am

Hrm.

My gas mileage is super consistent (check the fuelly link in my sig).

I was at my bro-in-laws today, and I took my Blur over to use his battery tender. No need, just wanted to try it out. It was fully charged in probably 5 minutes. But I left it on for a bit, so the battery was disconnected for over 30 minutes. (I turned it back on when I reattached everything just to check, maybe I shouldn't have done that in a garage!)

I was youtubing videos to listen to 'rich' and 'lean' conditions. I think overall my scooter is good. In the garage, on center stand, the rev dropped pretty quickly after releasing throttle.

Now that I think more on it, these pops tend to often when I'm between 10 to 20mph... Couple that with me noticing it more during coasting conditions, and I'm guessing it has something to do with gear switching and the EFI struggling a little when it's borderline? 'Crawl and go' scenarios, gas occasionally a little rich?

I'll go for a ride tomorrow and see if it sounds better, and try again to force the pops. Again, it's not that frequent, but it happens. It doesn't bother me aesthetically, but I'd hate it if I'm letting a potentially bad symptom go without a response.

Edwub · Post by **Edwub** » Tue Apr 24, 2012 4:46 pm

NathanielSalzman wrote:Your O2 sensor could be malfunctioning or your EFI computer module might be faulty or need to be reset. You might also have partially clogged injector. An easy way to reset the module would be to disconnect your battery for 30 minutes, then start the scooter back up. The computer will have to take fresh O2 readings and that just might do the trick.

On Sunday, I left the Blur hooked up to his battery tender for a few hours while I ran some errands. Came back, wheeled it out of the garage, and turned it on outside. Let it sit for a few minutes.

Granted, I've only ridden it to work and back on Monday and now to work this morning, but I think your advice may have worked. I really, really looked for it this morning. It "popped" a lot less than I'm used to. In fact, I actually noticed something was weird because I didn't hear it.

It may be wishful thinking, but I think your advice really did help!! Thanks!

Lotrat · Post by **Lotrat** » Wed Apr 25, 2012 2:08 am

Dooglas wrote:
easy wrote:sounds like exhaust leak
This would be my first suspicion as well.

x3.

Engine temp and ambient temp can play a part in leaks. Did you check the exhaust?

Edwub · Post by **Edwub** » Wed Apr 25, 2012 2:52 am

I'll check this as well, if I can figure out the best way to do it. If there is an actual exhaust leak, would the 'reset' I did actually accomplish anything or be able to compensate for it? Assuming a leak formed that didn't use to be there....(asking because, as I posted above, I want to say it got better but it may have been wishful thinking...)

Re checking:

1) Rub soapy water over the exhaust pipe, turn on, and wait to see if any bubbles form? Rev throttle a little and look for bubbles?

2) I read something about a smoke machine helping - I have plenty of access to dry ice and water. Figured I could whip up a quick fog and waft it around when I'm at work tomorrow.

The thought is I'm basically looking for an air leak, so should see bubbles or see fog being blown away from anyplace other than the business end? Which would be bad. Do I need to figure out a way to remove the cover to check the whole thing, or can I leave it on and just check the exposed surfaces first?

PeteH · Post by **PeteH** » Wed Apr 25, 2012 2:57 am

I don't know about thr Blur, but the Buddy has the blower fan that vents out the bottom. This would probably dissipate any smoke/mist, making it difficult to use smoke to find the leak. I think you should use your fingertips near the exhaust header, any curves in the pipe, and all along its length feeling for puffs that shoudn't be there.

Lotrat · Post by **Lotrat** » Wed Apr 25, 2012 4:40 am

Nah, just check to see if anything is loose.

#13 should be torqued to 1.0 - 1.2 kg-m
#10 should be tight
If #9 or #10 are damaged, they may cause a leak.

Post by **ericalm** » Thu Apr 26, 2012 5:40 am

Bad rollers can also cause this kind of sound.

KevinD · Post by **KevinD** » Sat May 12, 2012 4:12 pm

I had the same issue with my new Prima pipe. Took it back to the dealer they put in a new gasket, some type of sealer and then used loctite on the bolts to keep them from coming loose again. She was really loud and the popping was almost everytime I got off the throttle. All better now.

Edwub · Post by **Edwub** » Wed Aug 29, 2012 6:40 pm

/bump

I forgot about this, but today it was pretty noticeable. You know when you're making popcorn in the microwave...and towards the end you get that "pop pop .... pop pop pop pop...............pop"

It was doing that this morning, and yesterday morning as well. Sounded like the remants of popcorn in the microwave: it was clearly audible, but not overtly loud (not a BANG). Wasn't overly sharp either. But it wasn't just one or two, today there was like 15 to 20 pops the first half mile.

Was fine yesterday evening leaving work - so it's morning related? Chillier air? I think it was fine the last few weeks. It pops occasionally in the back, but all of a sudden it got weirder again. Exhaust seems fine, checked several times for leaks.

I usually have the scooter running for about two minutes each morning before I ride it - enough time to fold the cover and put it in a bag, then put on my jacket, helmet, and gloves. (I don't just twist and go without any warm up).