Turbo 5VZ... Random dead spot bucking/jerking while cruising - Page 3 - Toyota Tacoma Forum
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post #21 of 28 (permalink) Old 02-25-2019, 02:15 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

I feel confused, but at the same time that you're confirming these initial thoughts:

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Originally Posted by garetcurry View Post
I think the O2 sensor takes it's reading of the voltage from the middle of the sensor voltage range on my truck. I'm not the only user that has experienced that at 0.05 volts, I get the richest AFR's possible (12). Yet, at 0 volts, it equates to the truck running at 14.7 AFR. From 0.05 to 3.36 volts controls the O2 sensor from 12.01 - 14.6 AFR. Now I understand he has a narrow band sensor since he has his Bank1 high voltage set to 1.1 volts, but does the sensor follow the same weird wide band behavior described previously (this is a rhetorical question)?
So, in a way, you were telling the truck "everything is f..." BAM!
Whatever the case, I'm glad you can experience the boost without jerking around. Please attach your AEM FIC file so I can graph your fuel map. I want to see your fueling curve.

-gmc

Last edited by garetcurry; 02-25-2019 at 02:18 PM.
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post #22 of 28 (permalink) Old 06-11-2019, 02:03 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Closing the loop (get it?) on the bucking/jerking, I finally 100% cured mine. Does anyone still read this thread? Probably not, but posting it for historical reference. I already identified that the 98 ECU doesn't like when the AEM FIC 6 "turns on" and starts modifying either the O2 sensor or the fuel injectors. I filled in all cells with data and that helped tremendously since there were no more 0 values but at around 3-4 lbs of boost the bucking would always return.

I found out that when the fuel values switched from a negative amount (I was pulling fuel at vacuum) to a positive amount, it would still at times calculate a "0" fuel value. Once it did it would buck until I gave it more throttle. I changed ALL of the cells to be a minimum of +0.8 and it's completely gone. It does mean my LTFT's are running at about -6% in vacuum, but that's not bad enough to cause any issues with my tune. Once it enters boost it's pretty close to a perfect 0 LTFT. Hoping this helps someone in the future.

S/C'd at 11 PSI, AEM F/IC 6, methanol injection and a whole bunch more.
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post #23 of 28 (permalink) Old 06-11-2019, 07:11 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Thanks for posting the solution to the bucking mystery. If you hadn't dived down into the data (numbers; values) you probably wouldn't have ever figured out what was going on.

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post #24 of 28 (permalink) Old 06-12-2019, 04:34 PM Thread Starter
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Quote:
Originally Posted by Gamefreakgc View Post
Closing the loop (get it?) on the bucking/jerking, I finally 100% cured mine. Does anyone still read this thread? Probably not, but posting it for historical reference. I already identified that the 98 ECU doesn't like when the AEM FIC 6 "turns on" and starts modifying either the O2 sensor or the fuel injectors. I filled in all cells with data and that helped tremendously since there were no more 0 values but at around 3-4 lbs of boost the bucking would always return.

I found out that when the fuel values switched from a negative amount (I was pulling fuel at vacuum) to a positive amount, it would still at times calculate a "0" fuel value. Once it did it would buck until I gave it more throttle. I changed ALL of the cells to be a minimum of +0.8 and it's completely gone. It does mean my LTFT's are running at about -6% in vacuum, but that's not bad enough to cause any issues with my tune. Once it enters boost it's pretty close to a perfect 0 LTFT. Hoping this helps someone in the future.
I still lurk this forum, I am glad you posted this because I still have my bucking/jerking issue as well. When I filled in the whole o2 table it did help but never actually went away. Mine seems to only be right as vacuum turns into boost (0psi) at a freeway cruising speed, never has done it under acceleration. If I recall correctly my fuel table does start around 0-1psi so it may be because there is no AEM control while in vacuum. May have to try what you did as well and add values in vacuum.
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post #25 of 28 (permalink) Old 06-13-2019, 12:01 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Quote:
Originally Posted by Sean-Himself View Post
I still lurk this forum, I am glad you posted this because I still have my bucking/jerking issue as well. When I filled in the whole o2 table it did help but never actually went away. Mine seems to only be right as vacuum turns into boost (0psi) at a freeway cruising speed, never has done it under acceleration. If I recall correctly my fuel table does start around 0-1psi so it may be because there is no AEM control while in vacuum. May have to try what you did as well and add values in vacuum.
Yes, that's exactly how mine started since I initially had my fuel map the same way. Try just adding just the +0.8 to all cells and I'm confident it will go away.

S/C'd at 11 PSI, AEM F/IC 6, methanol injection and a whole bunch more.
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post #26 of 28 (permalink) Old 06-13-2019, 04:01 PM Thread Starter
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

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Originally Posted by Gamefreakgc View Post
Yes, that's exactly how mine started since I initially had my fuel map the same way. Try just adding just the +0.8 to all cells and I'm confident it will go away.
I adjusted the fuel map last night and reset the memory so Ill give it a few weeks and see how she does!
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post #27 of 28 (permalink) Old 06-26-2019, 12:07 PM Thread Starter
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Well, I was able to take the 4Runner on a decent drive. Nothing abnormal noticed since adjusting the fuel map! Such a great relief
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post #28 of 28 (permalink) Old 06-26-2019, 12:39 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Wow. Praise to Gamefreakgc's efforts and results.

From an electrical stand point, I would hypothesis that maybe the AEM FIC "turning on" is creating a noise spike towards the Toyota ECU. Maybe.

-gmc
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