Stalling out

It could have a dirty throttle body causing those symptoms. Take it off and clean the front and back of the blades real good.

Something else to think about might be a fuel filter. Back in the day that was a common symptom of a fuel filter that was starting to get really plugged... With more modern gas nowadays it seems that is not as much of a problem.

Just to add to this discussion my mileage has never been in the 30's like you my slingshot always seems to report average mpg of more like 27 mpg, and having just recently installed my DDM CAI I can say my throttle body looked very clean. Also I should add that the only time my idle drops down and feels close to stalling is when I first back out of the driveway for a ride that first time I take my foot off the gas in reverse before putting it into first it will drop very low and seems to be right on the verge of stalling before recovering - - I never really thought much of it, always figured it was just because the motor was still cold

Also I suspect our California 91 octane 10% ethanol fuel might be the cause of us not getting as good of mileage as those who get non ethanol 93 octane - its a known fact that fuel with ethanol will never get as good mileage as non ethanol fuel and higher octane should also give them an advantage.

according to my service book the fuel filter is in the fuel pump and in section 7.11 of the book it says this:

Fuel Filter Replacement

The fuel pump contains two filters. Both are non serviceable. If filters are clogged with debris, replace the fuel pump assembly as a whole unit.

Edit, as a side note I would think if the fuel filters were clogged fuel starvation at higher RPM would also be a problem

Quote from Edward Neal

Just to add to this discussion my mileage has never been in the 30's like you my slingshot always seems to report average mpg of more like 27 mpg....................

Roger that!

Also I should add that the only time my idle drops down and feels close to stalling is when I first back out of the driveway for a ride that first time I take my foot off the gas in reverse before putting it into first it will drop very low and seems to be right on the verge of stalling before recovering - - I never really thought much of it, always figured it was just because the motor was still cold

And Roger That!

Bill

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Clean throttle body and air filter should insure good air flow, but perhaps you might run some Sea Foam in your next tank to make sure the injectors and the fuel system components are also nice and clean

My 15 would sputter when stopping. Just had the dealer check and reflash the ecu. I think there was a recall for this. Could be wrong. As far as seafoam, I read it's voodoo marketing. Never have used gas additives in my life so far and never had any issues. Oh, except stabil for storing over the winter.

My 2018 sputtered and stumbled when I'd come to a stop when I first got it. After a thousand miles or so, it straightened out. No idea why. Sorry I can't be of any help.

Had to make a Walmart run for some other things so I figured it would be a good time to follow my own advice - its been some time since I last did this

Quote from SoCal

I just cleaned my throttlebody and it was probably one of the easiest things I’ve ever done. Should you do it just make sure that you don’t over tighten any of the four bolts when reinstalling.

Also do not move the butterfly as it is controlled by gears and you don’t wanna screw that up. A toothbrush a light cloth and some carb cleaner will get the job done.

I have my K & N filter soaking and being washed right now and will reinstall later on this afternoon when it is dry. Hopefully this will be the fix.

Clean!

Dirty!!

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Thanks for the tip. I just added that to my list of things to do next weekend.

Quote from VV11B40

My 15 would sputter when stopping. Just had the dealer check and reflash the ecu. I think there was a recall for this. Could be wrong. As far as seafoam, I read it's voodoo marketing. Never have used gas additives in my life so far and never had any issues. Oh, except stabil for storing over the winter.

Almost all gasoline has additives and from what I have read over the years its these additives and the quality and type of these additives that distinguish higher quality gasoline from not so great gasolines I when you think about it almost all of the gasoline in the country comes out of a rather small number of refineries it is the additives added after the fact that makes a top tier fuel like Chevron fuel superior to the fuel sold by some no name station. - - I am no expert on these things, but I have seen Sea foam come highly recommended by fellow members here who I know are thousands of times more knowledgable than I am about such things, as such I figure WTF if people I trust have been using it for years and highly recommend it then why not?

Oh and as a side note Sea Foam can also be used as a stabilizer they say it will stabilize diesel or gas for up to 2 years

Quote from SoCal

ultrascott Really appreciate the heads up on this and now that you mention it it makes perfect sense whether it’s the culprit or not. I’ve always had gas mileage envy of others who were saying they’re getting mileage in the 30s while mine always stays at 27 no matter what. Perhaps cleaning the throttlebody would help in this department as well. I found this article and although I may try it I think it’s best to remove the throttlebody and clean it separately. Once again thank you!

https://rxmechanic.com/how-to-…body-without-removing-it/

no problem. We see dirty throttle body’s cause all sorts of issues at the GM dealership i work at. My slingshot is around 29.5mpg so far. I’d like to see those 30’s also. Let me know if this helped or not please,I’m curious.

A couple years ago, my engine would sometimes stumble under acceleration if I shifted gears around 4K. My first fear was the fuel pump going bad. Not wanting to pull the rear apart when I didn't know exactly what the problem was (along with how much Polaris charges for a fuel pump assembly).

I initially found a simple, much less expensive replacement for the fuel pump that fits in place of the fuel pump in the fuel pump assembly. See this post - https://www.fuelpumpfactory.co…2015-2020-replaces-252124.

I then tried running a can of Heet fuel line additive. and refilled the fuel tank before trying a can of Sea Foam in the tank. I used a full can and again went thru 2 tanks. After these 2 doses, the stumbling cleared up. I now try to remember to add a can of Sea Foam (or Walmart's cheaper clone) every other month or so.

Obviously, in a TB system, any additive in the gasoline is not going to have any effect as far as keeping the TB clean, so the approac in the linked article above may help in cases of dirty TB valves/sensors.

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A stumble or stall as the engine winds down to an idle coming to a stop can be caused by a vacuum or exhaust manifold/header leak.

If your cleaning doesn't fix it I would check the usual culprits. The vacuum cap on the intake manifold under the throttle body, the vacuum cap (or hoses if you are CA compliant) on the fuel vapor recovery line at the rear of the valve cover, and your manifold/header bolts.

If none of this or what you have done resolves the problem I would replace the O2 sensor.

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