Fix for mt stumble condition dicussion

The auto has the new update to improve the low end stumble, so this thread is to discuss the need/want of a fix for us mt people. This thread is not about discussing ov tune.

 

I've never experienced said stumble condition. Can you describe this issue?

 

https://www.tacomaworld.com/threads...ota-for-stumble-condition-tsb-0062-18.559435/

 

mine happens a dozen times a day. Between 1500-2000rpm (usually around 1800rpm) the engine stumbles considerably, it feels like a miss or a hole in the throttle map. It can happen in any gear but seems to be more pronounced under hard acceleration. If I go half throttle until 2000rpm I can sometimes avoid the stumble.

 

You're saying it feels like a misfiring within that rpm range? I agree the truck feels underpowered in that rpm window.

 

I have the stumble in the MT as well, basically have to play the perfect throttle/RPM game. Too much too early, stumble! Too much to fast, stumble! Even with higher RPMs I get this tug, tug, tug feeling when giving it some gas.

I don't fall in VIN for the CPS replacement, not sure if thats the culprit, but a fix for the stumble would be nice!

 

yes, it feels like a misfire. It's not just a lack of power, in my case the truck noticeably bucks when the engine stumbles.

 

This happens to me. Is more pronounced when cold and I live at sea level.

 

One thing to try (I can't remember where it was said) is to try the long TCS Off button press while stopped. I had a set of stumbles happening on a very hot day and I thought that I saw the TCS light flicker even though I was gently pulling away from a stop. The long press seemed to solve the problem. Some folks (include me) also feel that the engine seems slightly better driving around with TRAC and TCS off. I do this mainly on dry / hot days.

 

Have you guys tried switching gas? Mine would buck and run not great when I used the cheap gas that was by my house. I have since switched to top tier and don’t have the problem any more.
Also, shifting at higher RPMs seems to help a lot as well. This engine likes the higher rev band. We also have a heavy flywheel to move instead of a torque converter so it needs the higher revs.

 

I feel it too. Lower RPMs for sure.

 

I live at altitude (~5300') and I notice it most (every day) in cold weather conditions, but have had it happen infrequently during the summer as well. The truck will intermittently hesitate/stumble while accelerating, it feels like I let off the gas for a second and then step back on it, it lasts for a split second and then drives normal again. It does not have to be from a stop.

I have a manual transmission and I usually shift from 1st to 2nd and from 2nd to 3rd around 3k rpms, which will drop the rpms down to ~1500 after shifting; right around and only around ~1500 rpms does the hesitation happen (I have not noticed it happening any other time), but not every time, only randomly.

I've noticed it most during colder weather, I don't get any codes/CELs, I've tried different octanes (86, 91) from different gas stations (costco, conoco), I've made sure there are no air leaks in the intake system, I do not have any engine mods, it doesn't matter if the truck is cold or fully warmed up, it doesn't matter if I'm on a hill or flat ground, the truck has never stalled from this, and this is happening on a normal paved road that is not slick or iced.

Took it to the dealer and he told me that this was normal operation of the Otto/Atkinson motor and that I was shifting too low (I normally shift around 3k rpm)... Basically, if I didn’t want to feel the hesitation, I need to rev it out more so the needle doesn’t drop below 1500 rpm between shifts. He said that that must be where the motor is switching over from Otto to Atkinson and for whatever reason (outside temp, throttle position, etc) the motor stumbles right there.

 

Not sure if it's related. But in the past I have felt the truck clunk when I floor it in 2nd gear. I like to be gentle with my acceleration and let the truck warm up smoothly so this probably why I don't have an experience with stumbling.

 

That's not a miss or a stumble. That's expecting the motor to do something it's not going to do, provide low end torque.
My truck runs exactly as designed. I very seldom am ever below 2K RPM unless I am putting around a parking lot.

 

i know what you're talking about, when the motor is overwhelmed and stumbles almost like lugging. but this is not that. this stumble thing shows under normal or even light load. i had it with an empty truck, only me in it, before i got her tuned. can't say for sure any cause, but i can say that my OV tune's map fixed the issue.

 

@MOC221_ @Trident904 maybe a TSB is needed?

 

Maybe? lol

Edit: I don't think you're genuinely interested in any of this bud, and TBH people are discussing a known problem that is actually a serious issue with the stock calibration (on some trucks).

 

Good for you and your truck, honestly.

There were no less than two TSBs released last month to address driveability issues. I think Toyota is receiving far more "feedback" than people think.

In before latest monthly Taco sales figures.

 

BTW, props to everyone who is providing feedback to Toyota on this issue with M/T trucks. That's how change happens.

Or, we could sit back and just take it. Yep, no problem that the truck will completely fall on it's face (after a split second of acceleration). That's perfect in an intersection.

Now - one thing has become obvious already, in that people are discussing two and possibly 3 different symptoms:

1. You give the truck a moderate to heavy throttle stab at low speed (it can happen in 1st gear) - the truck starts to move out, then suddenly noses over and loses power for a second or so, then takes off like a bat out of hell. Sometimes this "buck" will repeat several times. That to me is "the stumble". My truck would do this from day one, and yes OVtune killed that (sorry OP);

2. You're driving along in a higher gear at say 1500-1800 rpm and with some application of throttle the truck will feel like its very quickly losing a slight amount of power and just as quickly getting it back. That to me is the "stutter" or misfire feeling. I'm VERY familiar with it, as it was present from new. OVtune killed that for me (sorry OP) temporarily, but unfortunately over the course of about 2000km I've gotten a slight stutter back when not up to temperature.

Another thing you all need to know, these trucks can behave very differently with nearly identical operating conditions. A good example of that is when a new tune version is being trialed. My truck might stutter, but another guys truck will not and he thinks I'm on crack. That can happen running the same tune file, same M/Y truck and the exact same model, same fuel Octane rating. The tuner changes a couple of things based on my techstream logs and feedback - truck no longer stutters (and the other guy is good too).
There is variability in these trucks. That's one reason why some experience problems and some don't.

 

While I applaud the idea of this thread, trying to knock down OVtune discussion right out of the gate is perhaps not the way to go. I understand you want Toyota to fix it and I agree.
The thing is there is a lot of knowledge and experience regarding the stock calibration and how OVtune has improved upon it out there. Lots of stuff was tried and plenty of data was gathered. There are a couple of guys who frequent those threads that are very knowledgeable when it comes to tuning and this engine.

Again, I agree that it shouldn't turn into "just buy OVtune". That won't help at all.