Stumble during warm up?
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Road Captain
Joined: Mar 2007
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Stumble during warm up?
2015 Sporty 1200, Ness big sucker, wild pig slip ons and micro efi tuner. I noticed that while its warming up sometimes it'll stumble for a second then recover. Almost like when a carbed bike has a float level too low and starves for a second. Wondering if its just because the bike is switching fuel injector values or something else electronic related? Anyone else have this happen?
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Road Captain
Joined: Mar 2007
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Ok Thanks, I remember my carbed bikes did it sometimes too. If i dont let it fully warm up I don't notice it happening. On a side note:totally different animal but I have had various GM cars over the years including my current 19 Acadia, and when the injectors switch from dual to single during warm up after like 38 seconds on a cold start sure enough it'll stumble. On my 16 GM 3.6 i did plugs and an intake manifold gasket and it did the same Gdam thing because thats how its designed.
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Road Captain
Joined: Mar 2007
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What would I be tuning out? What is happening ?I am actually thinking of switching tuners, funny you mentioned that.
Road Warrior
Joined: Jul 2013
Posts: 1,649
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From: Indianapolis
Two things in the EFI could be contributing to the stumble.
1. at about a engine temp of 86 F (2014+ Sportsters, 2007-2013 149 F) the ECU enters closed loop and starts to adjust the injector pulse width using O2 sensor feed back.
IF the tune is set to enable closed loop mode.
2. there is a warmup enrichment table that adds fuel like a choke would. It adds more fuel when the engine is colder when starting
The added fuel decreases over time until you are at the AFR/Lambda in the Air Fuel table, usually a minute to 90 seconds (maybe a little longer when colder)
One other thing is the idle speed, it is also temperature controlled, you will have a higher idle speed when starting cold, it will decrease as the engine warms up.
The far left column in the AFR/Lambda table 20 Kpa would only be used during deceleration normally when the throttle is closed.
The idle MAP values would be in the 30-40 MAP range in the AFR/Lambda table
(The VE Tables are Throttle position and RPM based)
1. at about a engine temp of 86 F (2014+ Sportsters, 2007-2013 149 F) the ECU enters closed loop and starts to adjust the injector pulse width using O2 sensor feed back.
IF the tune is set to enable closed loop mode.
2. there is a warmup enrichment table that adds fuel like a choke would. It adds more fuel when the engine is colder when starting
The added fuel decreases over time until you are at the AFR/Lambda in the Air Fuel table, usually a minute to 90 seconds (maybe a little longer when colder)
One other thing is the idle speed, it is also temperature controlled, you will have a higher idle speed when starting cold, it will decrease as the engine warms up.
The far left column in the AFR/Lambda table 20 Kpa would only be used during deceleration normally when the throttle is closed.
The idle MAP values would be in the 30-40 MAP range in the AFR/Lambda table
(The VE Tables are Throttle position and RPM based)
Last edited by shanneba; Jan 14, 2020 at 07:49 PM.
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Road Warrior
Joined: Sep 2017
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From: over the mountain
There is a long thread on this over on the XL forum. But this is what Roy Hartman at power vision said do and it did work .This is in the left fuel column of the fuel table. The thread at XL forum tells how much to add.
Thank you for contacting Dynojet Research, we appreciate your interest and support of our products. The warmup enrichment is only in play for the first minute of run time. About one minute after starting, warmup enrichment is over, and you are in the regular tune. If the engine runs poorly after one minute, but before the engine is fully up to temp, I would suspect the engine is a bit lean, at least at idle. Try adding a bit a fuel around idle, and see how the engine responds.
Roy HartmanI’m jumping in to answer as Roy has already left for the day.
You are correct. I would suggest adding fuel by increasing both VE tables at idle. 0 percent throttle around a 1000 RPM. And see if that helps your issue. Please let us know if you have any other questions.
Patrick Daniels
Thank you for contacting Dynojet Research, we appreciate your interest and support of our products. The warmup enrichment is only in play for the first minute of run time. About one minute after starting, warmup enrichment is over, and you are in the regular tune. If the engine runs poorly after one minute, but before the engine is fully up to temp, I would suspect the engine is a bit lean, at least at idle. Try adding a bit a fuel around idle, and see how the engine responds.
Roy HartmanI’m jumping in to answer as Roy has already left for the day.
You are correct. I would suggest adding fuel by increasing both VE tables at idle. 0 percent throttle around a 1000 RPM. And see if that helps your issue. Please let us know if you have any other questions.
Patrick Daniels
Last edited by apache snow; Jan 14, 2020 at 08:36 PM.
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Road Captain
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Thanks for the responses. I suspect since I have the micro efi tuner installed, which disables the O2 sensors completely IIRC, whats going on is the transition to closed loop and no input from any O2 sensors I guess causing the ECM to "look" for something that isn't there??. Funny thing is even after trying like 6 or 7 tunes from fuelmoto, mostly for decel pop and weakish midrange, my best results were with one of their tunes AND adding about 4 percent enrichment on top of that tune in the the 2 to 4K RPM range by turning the center pot up while connected to my laptop to make sure what value I was adding. Fuel moto tunes of throwing more fuel at closed throttle at those rpm's helped but caused a mad mid range roll on hesitation. So I went with a moderate tune and just added as I stated above. Sure enough very very little decel pop, and strong strong midrange. My opinion is that the Ness big sucker and all full open air cleaners flow ALOT more air than just dropping a K and N in the ham can stock air box. I've done both on carbed bikes in the past and it ALWAYS opened up a lot of carb farts if I left the jetting or needle the same as I did with the ham can air box and a drop in K and N. So tuner manufacturers saying "any" open element air cleaner and most generic slip ons are all the same tune is totally wrong, and just gets you going. For me the jury is still out on the micro efi to be honest. Their customer service is top notch, I contacted them and was told send it back if I want to. I'm still deciding actually. Trouble is I'm in PA and riding weather is far and few here in January although last weekend was in the low 60's here!! But thats a fluke so I have to wait and see if this is a good combo or not.
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