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Discussion Starter · #1 ·
Hello,
Its been a while since Ive visited...this is crazy.

anyway, my fiance's tacoma (a 1999 V6 5spd 4x4) doesnt stay in closed loop. everything operates seemingly normal, however whenever the throttle is pushed down to accelerate quickly (like an on ramp) my scan tool shows that the computer will jump into open loop for a second to 3 seconds and then back to closed loop. it will also do this under deceleration.

at an idle or very very light throttle driving it stays closed. is this normal? engine performance and economy is otherwise totally normal, no check engine lights ect.
I was just curious because my 97 tacoma with the 2.7 does not do this...

thanks in advance
-Dan
 

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Depending on the amount of throttle used befor it goes into open loop it may or may not be normal operation.

Normally it takes near full throttle to trip open loop or be at 80% throttle or higher for a given amount of time. It should not be going into open loop from slight to moderate acceleration at less then full throttle.

If that is what it is doing, then it is not normal and it may indicated a problem. Normally when I see this, it turns out to be that the mix for what ever reason is going way to lean or rich and the O2 sensor is locking out. Without a good O2 sensor signal the ECU will drop into open loop mode to protect the engine. Other things that can cause this is a bad throttle possition sensor that reports the wrong throttle possition to the ECU, a bad MAF sensor that is not properly metering and reporting the amount of air entering the engine and so on.

From what you describe, I would say that what you are seeing is not normal operation.
 

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Discussion Starter · #4 ·
Thanks,
The same day I had discovered this problem I also cleaned the MAF, it was pretty dirty...according to the scan tool graph the o2 sensors are working how they should, but I havnt tested them beyond that. TPS is set correctly and voltage increases smoothly through the entire sweep. Id say it only takes about 50-60% throttle before it happens.

Is it normal for it to go to open loop under deceleration too? or only acceleration?

thanks
-Dan
 

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It is normal to go into open loop when decelerating with the the trottle all the way closed above 1500 RPM. This is one of the fuel cut modes and the injectors should come back online at about 1500 RPM and once the O2 sensor sees the mixture change it should drop back into closed loop.
 

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Discussion Starter · #6 ·
ok..cool well then Im not gonna really worry about it then. thanks again for the info, thats good to know.

-Dan
 

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Hi Gadget
I had my truck tuned at the only tuning shop in Ontario, Canada that i could find that was apparently familiar with Split Second products on Saturday.
I installed the 2.2" Supergrip pulley before the tuning was done.
Although the truck appears to have more power now and the high rpm pinging is gone it is doing some disturbing things now.
It is bucking or hesitating while under full throttle at times. It feels like someone slammed on the brakes for a second or two while the truck is excelerating. It does this in various gears but mostly 5th gear under full throttle.
The engine light also came on during the tuning and is still on.
Any ideas as to what is going on here? Is there a tuner near Toronto, Ontario, Canada that actually knows what they are doing? This has been very frustrating to say the least.
 

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Its really strange because before the tuning was done it was running fairly well aside from the pinging under full throttle in 5th. It has more power now but hesitates from time to time.
 

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scott bardwell said:
Its really strange because before the tuning was done it was running fairly well aside from the pinging under full throttle in 5th. It has more power now but hesitates from time to time.
Scott, my best advice is to learn to tune yourself. If you get a scan tool and a wideband setup, you can do it. All you need to do is follow Gadget's U-Tune guide he has on his web site. I was intimidated by the tuning process too because I am "old school" and not skilled with computer controlled cars or computers for that matter. My friend needed to tune his truck so we got all the tools and learned together. After you get into it, it's actually pretty easy.

Dave
 

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I had considered that but i thought i had found someone who could probably do a better job than me and i wanted it to be done right the first time. Now that i spent $200 (Can) on the tuning Saturday i don't really want buy the scan tool etc AND learn how to tune it myself. I have spent way too much money on this truck already and wish i just would of just left it stock ( with the lift, tires and rims of course)
 

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scott bardwell said:
I had considered that but i thought i had found someone who could probably do a better job than me and i wanted it to be done right the first time. Now that i spent $200 (Can) on the tuning Saturday i don't really want buy the scan tool etc AND learn how to tune it myself. I have spent way too much money on this truck already and wish i just would of just left it stock ( with the lift, tires and rims of course)
From my own experiences I can tell you that when your truck is not tuned and you rely on others to tune your truck (I have spent over 600 on "tuners" and dyno time) and it still runs like shit, you get frustrated and wish you had left it stock. That's only natural. Now that my truck is tuned properly, all is good and I don't think about the money I spent. I'm all smiles now and my truck has never run better. All I can say is don't get discouraged. I don't know how far away you are from Matt (Wisctaco). Sounds like he knows what he's doing with tuning. Maybe you guys could get together and he could help you out.

Dave
 

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Thats a nice set-up you have there! I hear what you are saying and you are right. Where does Wisctaco live? I live in Ontario, Canada about 45 minutes from Toronto. Do you know his email address? I would love to get my truck running the way i know it should be. Thanks for your help!
 

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scott bardwell said:
Thats a nice set-up you have there! I hear what you are saying and you are right. Where does Wisctaco live? I live in Ontario, Canada about 45 minutes from Toronto. Do you know his email address? I would love to get my truck running the way i know it should be. Thanks for your help!
As Matt's "handle" (Wisctaco) suggests, he lives in Wisconsin. Look him up on the members list and send him a PM or an E-mail. I have talked to him before. He seems like a nice guy. Take a trip to Northern California and we will tighten you up.

Dave

Edit: Actually Matt goes by Wisctaco04.
 

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Thanks for the offer and i wish i lived a little closer where i could take you up on it but i live on the other side of Canada!!
 

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scott bardwell said:
Thanks for the offer and i wish i lived a little closer where i could take you up on it but i live on the other side of Canada!!
Aw come on, we have beer, cheese, and brats here! For how close you are to the east coast Gadget himself may tune it if you can get to him. I would gladly help you do it if you ever do make it this way. Otherwise I will be in the Fort Frances area this fall again but that's about the same distance to my house in Wisconsin for you. I sometimes wish I had left it stock but then I mash the skinny and get a huge grin. Yhe tuning process is actually pretty easy once you know what to do. The OBDII scan tool is great for other things besides tuning. I use that damn thing on other cars more than my truck. There is one that uses your laptop that is pretty cheap and will work just fine for tuning. Someone may chime in with a link for that. The AFR meter is your only big cost. Don't fret the tuning or $ spent. It's all worth it in the end. Matt
 
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