Turbo 5VZ... Random dead spot bucking/jerking while cruising - Toyota Tacoma Forum
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post #1 of 26 (permalink) Old 01-13-2019, 02:42 PM Thread Starter
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Turbo 5VZ... Random dead spot bucking/jerking while cruising

Hey guys, on to my next issue to sort out lol


98 4Runner

5VZ Turbo with FIC6

I have noticed while cruising usually freeway speeds around 60MPH, 2200RPM and between -10 and 0.

The 4Runner will buck/jerk pretty bad and I noticed that when it happens, the AFR's will shoot rich/lean/rich/lean. I took a short video of the wideband when it happened, sometimes it happens for longer periods of time.

I also took a few logs and captured one with the "engine load" signal that just drops off for a quick second (suspected to be my issue)

Looking for ideas of what it may be, my only idea is maybe the cam/crank wires on the FIC6. It was wired up according to this: https://www.toyota-4runner.org/3rd-g...lp-thread.html

Video: In worse cases it will go full rich to full lean. It is hard to catch it on tape since it is random...
Random surge by Sean Miller, on Flickr

graph:
Engine load drop by Sean Miller, on Flickr
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post #2 of 26 (permalink) Old 01-14-2019, 09:10 AM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

If it's a software/tuning issue: Attach your FIC6 map so I can scrub it to see if there are any "conflicting" values with other tables.

The only time I've encountered this, and the culprit was wiring, is when my AEM FIC wasn't getting power steadily because the power tie into the ignition was bad.

Didn't someone say you might have a bad TPS or fuel table issues in another thread?

https://www.customtacos.com/forum/2119327-post27.html
https://www.customtacos.com/forum/13...ml#post2119329
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-gmc

Last edited by garetcurry; 01-14-2019 at 09:19 AM. Reason: https://www.customtacos.com/forum/2119327-post27.html
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post #3 of 26 (permalink) Old 01-14-2019, 09:54 AM Thread Starter
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Quote:
Originally Posted by garetcurry View Post
If it's a software/tuning issue: Attach your FIC6 map so I can scrub it to see if there are any "conflicting" values with other tables.

The only time I've encountered this, and the culprit was wiring, is when my AEM FIC wasn't getting power steadily because the power tie into the ignition was bad.

Didn't someone say you might have a bad TPS or fuel table issues in another thread?

https://www.customtacos.com/forum/2119327-post27.html
https://www.customtacos.com/forum/13...ml#post2119329
First, when you say attach my map you mean like just a picture or something? I can do that after work but I can tell you now that my maps are zero'd out until boost and the issue normally happens while in vacuum.

I feel like wiring would cause this but all my connections seem to be good, I soldered all the "ties".

Someone did say TPS and I can see that causing it, my only issue with it is that it tested fine for voltage and resistance. Shouldn't I see a dead spot? Why would it only happen between 40-60MPH? I would rather it be a TPS issue over wiring though. I suppose I will start shopping for a TPS and just pull the trigger on that and see what happens. I wish it would just throw a code...
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post #4 of 26 (permalink) Old 01-14-2019, 03:12 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

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Originally Posted by Sean-Himself View Post
First, when you say attach my map you mean like just a picture or something? I can do that after work but I can tell you now that my maps are zero'd out until boost and the issue normally happens while in vacuum.
The AEM file. The .fi6 file. Put it in a .zip file, as I don't think CT.com accepts or allows .fi6 files.


Quote:
Originally Posted by Sean-Himself View Post
Someone did say TPS and I can see that causing it, my only issue with it is that it tested fine for voltage and resistance. Shouldn't I see a dead spot? Why would it only happen between 40-60MPH? I would rather it be a TPS issue over wiring though. I suppose I will start shopping for a TPS and just pull the trigger on that and see what happens. I wish it would just throw a code...
Maybe that's the sweet spot.

-gmc
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post #5 of 26 (permalink) Old 01-14-2019, 06:23 PM Thread Starter
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Quote:
Originally Posted by garetcurry View Post
The AEM file. The .fi6 file. Put it in a .zip file, as I don't think CT.com accepts or allows .fi6 files.




Maybe that's the sweet spot.


Hope this works.
Attached Files
File Type: zip Tune 2. Zipped.zip (24.8 KB, 2 views)
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post #6 of 26 (permalink) Old 01-15-2019, 09:12 AM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

I'm not seeing any conflicting cell values that are jumping out in front of me, but I did notice something.

Perhaps running your O2 in voltage mode and creating a voltage/O2 table might work. From the installation instructions:

“Voltage” mode - The F/IC outputs a voltage, which is determined by the
corresponding cells in the “O2 Map”. In the “Voltage” mode, for an “O2 Map” cell
value of 2.5, the F/IC will output 2.5 volts. In “Voltage” mode, a cell value of 0
makes no change, NOT an output voltage of 0 volts.

“Fixed” mode - The F/IC outputs a square wave that alternates between the Bank
Hi voltage and the Bank Lo voltage. The Bank Hi voltage, Bank Lo voltage, and
square wave period are set in the O2 section of the setup window. The pulse
width is determined by the cell value in the “O2 Map”. For a Bank Hi of 2, and
Bank Lo of 1, a period of 200 ms, and a cell value of 50, the F/IC will output 2
volts for 50 ms, 1 volt for 150ms, 2 volts for 50 ms, etc.

“Percent” mode - The F/IC will measure the O2 voltage, then modify it by the
percentage value in the “O2 Map”. For a measured value of 1 volt, a period of
200ms, and a cell value of 20, the F/IC will measure 1 volt for 5ms, then output
1.2 volts for 195ms, then measure again for 5ms, etc.

“Offset” mode - The F/IC will measure the O2 voltage, and then modify it by the
offset value in the O2 map. For a measured value of .7 volts, a period of 200ms,
and a cell value of -.25, the F/IC will measure 0.7volts for 5ms, then output 0.45
volts for 195ms, then measure again for 5ms, etc


My 02' 2rz liked percent mode. My 01' 5vz likes voltage mode. You could possibly be using a mode that (somehow) freaks out the ECM. I'm just guessing, but if you can skew your O2 a different way, it may work -- wild guess. Other than that... TPS or wiring gremlins?

-gmc
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post #7 of 26 (permalink) Old 01-15-2019, 01:55 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

I took a peek at your tune as well and found the problem.

Not everyone has encountered this issue, but I have as well. The bucking/surging where the AFR's jump all over is when you have two fuel maps active at the same time. This includes the O2 sensor map. It only does this when the second map become active, so when second fueling map goes from "0" to a value. For you, this is happening at 14.7 PSIA when your O2 and fuel tables become active at the same time. It also only bucks on the transition from 1 map being active, to 2. If you push into boost past that "transition" then it runs fine. If you were to remove the values in the O2 map at 14.7 and instead have it start skewing the O2 signal at 16.2, you'd notice the bucking start partial throttle acceleration when you hit 16.2 PSIA instead of 14.7. I never did get rid of it 100% but I've moved that "crossover" from around 15 PSIA to more like 21 PSIA and I'm normally in open loop at that point. Your saving grace here is that once the stock ECU sees it under heavy throttle or WOT, it ignores the O2 sensor skewing (and your O2 tune) and then the AEM is only running on one map again so the bucking goes away. It has something to do with how our stock Toyota ECU interprets the modified signal from the FIC 6.

If you want to minimize the bucking to as little as possible, zero out your fuel table in closed loop. It's going to take some time to figure out when the engine switches from closed loop to open loop (closed loop it takes in the O2 sensor readings, open loop ignores them) and obviously you don't want any spots with no tune. I'd start by zero'ing out all fuel table cells at 14.7 and maybe even 16.2 PSIA. This will at least push the "bucking" into the higher RPM's and better chance of the engine being in open loop. You have a turbo and not a S/C though, so you'll need to draw from your experience to know when it's building boost at what RPM's and what throttle level. The logs can be helpful if you overlay the TPS/throttle % and run a few partial throttle runs. Just know that once it enters open loop, your O2 map is completely ignored.

If you want, I can post up my maps on how I eliminated the bucking.

One other note, for sake of gas mileage you probably don't want everything skewing at 14.7 which is atmospheric pressure at sea level. Unless you live at elevation, you'll be burning through fuel when you don't need it. The AEM FIC software automatically smooths between the two values. What this means is, at 12.8 PSIA you have a value of 0, and 14.7 a value of -0.174, so skewing the O2 sensor to run rich. However, at 12.9 PSIA through 14.6 PSIA it's also skewing rich, on a sliding scale until it reaches -0.174 at 14.7. Make sense? Same goes with your fuel table, it's adding extra fuel from 0 at 12.8 PSIA to roughly +2.3 at 13.8, then +4.7 at 14.7 PSIA.

S/C'd with 2.1" pulley, 310cc injectors, AEM F/IC 6, methanol injection, Airaid intake, Doug Thorley headers and deckplate mod.

Last edited by Gamefreakgc; 01-15-2019 at 02:01 PM.
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post #8 of 26 (permalink) Old 01-15-2019, 03:12 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

My O2 begins skewing in voltage mode at 14.7 MAP and 1800 rpms (from 14.7 to 14 AFR). A voltage value somewhere around 2.6 volts according to my table. I'm not bucking.

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)?

I'm not sold on the two maps active diagnoses. Yeah, this can happen, but he has to be doing more of a severe tuning difference deal to make it buck in my experience. But... in offset mode with a -0.174 volt offset.. I mean, I have no idea how much of an AFR change that is on a Toyota narrowband O2 sensor, but maybe doing it that way is incompatible with the Toyota ECM clock speed?

Heck, he could have water in his charge pipe and when boost hits, it's just enough to suck the water to splash the MAF sensor (yes, this has happened to me) and make the truck freak out.

-gmc
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post #9 of 26 (permalink) Old 01-15-2019, 04:32 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

Quote:
Originally Posted by garetcurry View Post
My O2 begins skewing in voltage mode at 14.7 MAP and 1800 rpms (from 14.7 to 14 AFR). A voltage value somewhere around 2.6 volts according to my table. I'm not bucking.

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)?

I'm not sold on the two maps active diagnoses. Yeah, this can happen, but he has to be doing more of a severe tuning difference deal to make it buck in my experience. But... in offset mode with a -0.174 volt offset.. I mean, I have no idea how much of an AFR change that is on a Toyota narrowband O2 sensor, but maybe doing it that way is incompatible with the Toyota ECM clock speed?

Heck, he could have water in his charge pipe and when boost hits, it's just enough to suck the water to splash the MAF sensor (yes, this has happened to me) and make the truck freak out.
Like I said, not all experience this issue with the AEM unit. I was one of the unlucky ones and it took me weeks to figure it out. I'd adjust the tune again, and again, and again and nothing helped. I even tried negative fuel amount, so pulling fuel. Ended up zeroing out the entire fuel table and the problem went away completely, then I figured out what was going wrong.

Since I know you read the manual, this is what clued me in as to why it was bucking: "Keep it simple. Many times it is not necessary to use every function of the F/IC to obtain the desired engine performance. If the desired engine performance can be achieved by adjusting only two maps, use only the two maps. There is no benefit to adding fuel in one map and removing it in another." Or in this case, there is no benefit to adding fuel via the O2 skew, then adding even more via the fuel table. It just makes the ECU freak out with the mixed signals. The stuttering/bucking isn't like it slogging, it's literally cutting out fuel completely and then dumping it on, then cutting it out again, all several times a second. It feels like hitting the speed governor, if you've ever done that.

Once he zero's out a few rows of fuel table data, the problem will go away, I promise.

S/C'd with 2.1" pulley, 310cc injectors, AEM F/IC 6, methanol injection, Airaid intake, Doug Thorley headers and deckplate mod.
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post #10 of 26 (permalink) Old 01-15-2019, 05:34 PM
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Re: Turbo 5VZ... Random dead spot bucking/jerking while cruising

I figured it out.

Just uninstall the AEM FIC and your problem will go away.
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