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Discussion Starter #1
hi everyone.i have a v6 2008 6 speed. recently changed two primary o2 sensor and maf sensor with original ones.i have no catalytic converter.no cel or pending code on ecu.a wired acceleration problem i have experiencing is when i floor gas pedal car accelerate really good a while after this acceleration is not good as before and like something pulling car back. like it goes bad then back to good without any reason. everything is good. fuel filter is new air filter is new clutch is new. tps checked completely everything was in range and good . intake temp sensor checked. ignition system include plugs, wires, coils checked. injectors resistance checked.no misfire.cold start is perfect.no hesitation.i have noticed two thing
first:smell of unburnt fuel from exhaust specially when accelerate hard
two:engine like regain it's power for example when i stop behind traffic lights for a while after that acceleration is really good
i will be appreciated for any help or guess
 

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Where are you located? In most countries a 2008 Tiburon with not catalytic converters would cause all sorts of issues. I'm guessing you live in country with no emissions laws like South Africa?
If so your ECU tuning is way different than most everyone else. When you say you changed the sensors with original ones do you mean you replaced them with new OEM Hyundai ones or with ones that originally came on the car when you bought it?

Your issue could also be caused by a fault Throttle Position sensor.
 

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Discussion Starter #3
Where are you located? In most countries a 2008 Tiburon with not catalytic converters would cause all sorts of issues. I'm guessing you live in country with no emissions laws like South Africa?
If so your ECU tuning is way different than most everyone else. When you say you changed the sensors with original ones do you mean you replaced them with new OEM Hyundai ones or with ones that originally came on the car when you bought it?

Your issue could also be caused by a fault Throttle Position sensor.
i have removed my both catalytic converters and use o2 sensor spacer to prevent cel and there is no code for catalytic converter or any thing else in my ecu
i replaced maf and o2 sensors with oem ones
i have tested tps. every thing include resistance was good there wasn't any flat spot.but when i unplug tps it seems cars runs great. as i mentioned before there is no code stored in ecu
 

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So you tested the TPS and its resistance matches what is in a Hyundai Service Manual?

What else has been done to the car? Has the intake manifold been off for any reason?

If you are still running the stock air cleaner assembly check the hose between the MAF and throttle body. It should not have any holes or cracks.
 

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Discussion Starter #5 (Edited)
So you tested the TPS and its resistance matches what is in a Hyundai Service Manual?

What else has been done to the car? Has the intake manifold been off for any reason?

If you are still running the stock air cleaner assembly check the hose between the MAF and throttle body. It should not have any holes or cracks.
yes tps resistance is matched with what Hyundai said in manual
intake manifold was off for check spark plugs and wires but i tight its bolts and gasket was in good condition. any way i don't think a vacuum leak could be my problem because long term fuel trim for both bank is about 1% negative and i didn't hear any hiss sound from engine. the hoss between maf and throttle body is also in good condition and there is no crack as i checked. its become a puzzle for me why engine behave normally for a while and then its like a poor 4 cylinder engine or less
just for sure i have a p0335 code once so i checked my crankshaft position sensor there was no melted wires or anything wrong about sensor.could it go bad but still engine can go to high rpms?
 

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I have the same model as yours and had a similar issue.
My case was that when the engine was warmed up and hard accelerated once, the car would hesitate whenever gas is pressed.
When that happened, I opened the hood, jiggled the MAF connector, observed idling was becoming a little unstable or engine sound changed a little.
This happened a month after replacing MAF to a brand new one, so I never doubt it could've been the MAF, but turned out it was.
I think sometimes these parts can be defected out of the box.
You can also use OBD apps to see changes in MAF and fuel trim readings over driven time/distance.
 

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Discussion Starter #9
yo check your timing on your car....
i don't think it's timing problem because its intermittent. if something mechanical is my problem then it should be bad all the time
I have the same model as yours and had a similar issue.
My case was that when the engine was warmed up and hard accelerated once, the car would hesitate whenever gas is pressed.
When that happened, I opened the hood, jiggled the MAF connector, observed idling was becoming a little unstable or engine sound changed a little.
This happened a month after replacing MAF to a brand new one, so I never doubt it could've been the MAF, but turned out it was.
I think sometimes these parts can be defected out of the box.
You can also use OBD apps to see changes in MAF and fuel trim readings over driven time/distance.
i have replaced maf with oem one. do you mean it could be maf connector?
 

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expect your running rich. you said that you smell unburnt fuel. check your timing. youve checked the fuel delivery and know that you have a clean fuel and fuel pressure. but the cars not pulling. ive had this similar issue in the past. car can run as normal af, but when you want to accelerate a suburban is faster then you. you know you got good sparks. youve tested MAF, TPS im sure your intake is working properly. so why not check the timing. you could be off by one or 1.5 teeth, thats enough to hurt acceleration.
 

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Discussion Starter #12
expect your running rich. you said that you smell unburnt fuel. check your timing. youve checked the fuel delivery and know that you have a clean fuel and fuel pressure. but the cars not pulling. ive had this similar issue in the past. car can run as normal af, but when you want to accelerate a suburban is faster then you. you know you got good sparks. youve tested MAF, TPS im sure your intake is working properly. so why not check the timing. you could be off by one or 1.5 teeth, thats enough to hurt acceleration.
i should mention one thing
when i unplug tps car seems accelerate too much better but as i wrote before i have checked tps in every way. resistance was good and there was no flat spot and i have no cel for tps. so if it was timing problem,unplugging tps shouldn't make engine to accelerate better and I'm confused now
 

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Discussion Starter #13
is there a possibility that new o2 sensor could cause this situation? because before changing o2 sensors i have this sluggish acceleration problem but it wasn't while driving.it was permanent problem until i shut off engine and start it again but now this problem comes and goes while driving
can a bad ect sensor cause this situation too? without throwing any code
 

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The reason it may run better with the TPS unplugged is it forces the ECU into open loop mode and it doesn't use the O2 sensors because it doesn't know where the throttle is. One thing to check is to make sure you don't have the Idle Air Control Valve and TPS sensor connectors reversed. The are the same style plug, except the gray one goes to the TPS. And to answer your O2 question a bad or incorrect O2 sensor can cause all sorts of issues. Did you ever check your coil pack connections? There's 3 two wire connectors that tend to get brittle and break over time.
 

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Discussion Starter #16 (Edited)
no tps and idle valve didn't reversed. i can't believe that 4 o2 sensors are all defective but no code(two previous upstreams and two new upstreams).yes i have checked coil pack connections and make sure they are tight and right.only problem was connection pins that breaks for all 3 connections but they didn't lose or come off.i didn't have any misfire ever and idle is fine engine sound is fine too.
to answer your post on other topic:
reseting ecu didn't do any good effect. i have checked torque live data for all sensors except crankshaft and camshaft sensor. everything was fine but only thing that i notice was upstream o2 sensors acting strange on idle
i don't know why it can't be from defective o2 sensors because i change them for new oem ones and don't have any codes
forgot to tell some more thing.
Before I change o2 sensors I have experience a hesitation upon acceleration sometimes but again never had a cel or pending code.I mean sometimes when I floor gas pedal from a low rpm there was a hesitation and after that accelerate but not so fast.
but now and sometimes when I start engine drive it a while then shut it off for a while. Immediately after start engine I can feel a good acceleration and throttle response for a short while. I mean about 5 seconds or near that but after that it goes sluggish again.
 

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Discussion Starter #19
i have checked my coil pack primary and secondary resistance and it was all good also i never had a misfire.
i have also checked my crankshaft sensor it wasnt burnt or damaged but i had a p0335 code once last year that didn't come again and that was only time that i see this code and after i clear it, didn't show up at all
 
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