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Discussion Starter #1 (Edited)
update:new fuel pump fixed it
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hi everyone
it's 2007 v6
6 speed manual with 75000 miles
the problem is:
it doesn't accelerate as it should except sometimes for a short while
unfortunately it doesn't throw any code at all
i have changed ignition coil last night but with no improvement
it doesn't misfire, stall, jerk, hesitation or anything else
sometimes when i restart engine it accelerate prefect but just for a short time like 10 minutes
i don't know what to do after change o2 sensors, fuel filter, maf sensor, crankshaft position sensor and now ignition coil all with oem ones
fuel trims are about 1.6 to 3.6 rich for both banks that means engine have enough fuel
every one can help me i will do anything for him because now it's a nightmare
 

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it doesn't accelerate as it should
Some numbers would help, 50% of normal?

i have changed ignition coil last night but with no improvement
it doesn't misfire, stall, jerk, hesitation or anything else
Why did you change the coil if it's not misfiring?
i don't know what to do after change o2 sensors, fuel filter, maf sensor, crankshaft position sensor and now ignition coil all with oem ones
You replaced all these parts?
 

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Discussion Starter #3 (Edited)
Some numbers would help, 50% of normal?

Why did you change the coil if it's not misfiring?

You replaced all these parts?
maybe 70% of its power
because i think maybe it's a no code misfire situation
yes i have changed all these with oem ones also throttle sensor, engine coolant sensor and intake temperature sensor checked.all of them was good
timing checked and it was ok
car start without any problem
idle is fine too
i don't have catalytic converter on my car since 3 years ago
engine like regain it's power for example when i stop behind traffic lights my first acceleration after lights is really good but just for a few seconds, then back to slow
could it injectors problem? ecu? i don't know what to do
 

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Maybe you have a blocked exhaust. Take out the O2 sensor and see how it drives. Be careful with possible ignition on parts and maybe a shield might be needed.
 

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Drives : Nissan NV200 Flies : Rans S6ES
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i don't know what to do
Since you seem to like a good game of parts darts why not try replacing the brake light switch.
The engine ECU is programmed to automatically reduce engine power when it gets a signal from the brake pedal switch. When you press on the brake to try and slow the car down the last thing you want is the engine trying to push it forward. Anyway, if the brake pedal switch is faulty it could be sending spurious signals to the ECU causing your performance hit. If you search the forum for posts relating to brake light switch failure you'll see it's a common issue on Hyundai cars.

If your car has cruise control you might be able to use that to check the brake pedal inputs to the ECU. If the cruise control switches on but you are unable to "set" it, or if it cancels speed hold on it's own once if has been set, those would be symptoms of spurious brake pedal inputs.

Brake light switch faults wont necessarily effect the brake lights. There are two parts to the switch. One part sends the power to the brake lights, and the other part sends signals to the ECU, so you shouldn't assume the switch is good just because the brake lights appear to work properly.
 

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Discussion Starter #7
Since you seem to like a good game of parts darts why not try replacing the brake light switch.
The engine ECU is programmed to automatically reduce engine power when it gets a signal from the brake pedal switch. When you press on the brake to try and slow the car down the last thing you want is the engine trying to push it forward. Anyway, if the brake pedal switch is faulty it could be sending spurious signals to the ECU causing your performance hit. If you search the forum for posts relating to brake light switch failure you'll see it's a common issue on Hyundai cars.

If your car has cruise control you might be able to use that to check the brake pedal inputs to the ECU. If the cruise control switches on but you are unable to "set" it, or if it cancels speed hold on it's own once if has been set, those would be symptoms of spurious brake pedal inputs.

Brake light switch faults wont necessarily effect the brake lights. There are two parts to the switch. One part sends the power to the brake lights, and the other part sends signals to the ECU, so you shouldn't assume the switch is good just because the brake lights appear to work properly.
i have replace it about 6k miles ago but for sure i have used cruse control without any problem
could it fuel problems? although it seems long fuel trim is about 1.6 to 3.1 negative(rich)
i have checked timing belt and also timing marks on crankshaft pulley and cam sprocket
 

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Discussion Starter #8
Maybe you have a blocked exhaust. Take out the O2 sensor and see how it drives. Be careful with possible ignition on parts and maybe a shield might be needed.
i don't think so because i have removed catalytic converter materials from inside
 

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although it seems long fuel trim is about 1.6 to 3.1 negative(rich)
Fuel trim isn't what I would be looking at for this type of fault. When diagnosing performance issues I start by looking at the O2 sensor output voltages.
When your flooring the throttle the O2 sensor voltages should show high voltage (0.8~1.0V - rich). If the voltage is low that is telling you that there is not enough fuel being injected into the cylinders to burn the incoming air. Obviously the engine wont produce power if it isn't being supplied with enough fuel.
 

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Discussion Starter #10
Fuel trim isn't what I would be looking at for this type of fault. When diagnosing performance issues I start by looking at the O2 sensor output voltages.
When your flooring the throttle the O2 sensor voltages should show high voltage (0.8~1.0V - rich). If the voltage is low that is telling you that there is not enough fuel being injected into the cylinders to burn the incoming air. Obviously the engine wont produce power if it isn't being supplied with enough fuel.
i have checked o2 sensors too
they act normally when flooring gas pedal
i have checked my camshaft position sensor and find one strange thing
when i unplug it engine starts normally and there was no change
also try to scan for possible codes with torque app but after about just five minutes there was just a gray code for camshaft sensor not even pending code
 

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Discussion Starter #11
i have recorded a video from my upstream o2 sensors after a little drive. its in idle. o2 sensors are new and oem and there is no code or hesitation
 

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Discussion Starter #14
i have changed camshaft position sensor too but it didn't solve problem
checked injectors with multi meter all of them was good
also check for injector leaking or clogged and didn't see anything all of them was good
so what else could be
 

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Discussion Starter #19
Have you changed the air filter?
Weak fuel pump or dirty fuel filter?
fuel pump is my only suspect because fuel filter changed about 12k miles also cleaned about 3k miles ago with gunk injector cleaner spray
is it important to use oem fuel pump? if not how can i find out what fuel pump is suitable for this engine
 

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Changing a fuel pump is an expensive task. There should be a fuel pressure access point on the fuel rail and an inexpensive gauge can be used to monitor the fuel pressure when the engine is running. I would do this test before changing the pump. If you do have to change the pump, most people suggest using a quality [expensive] unit.
 
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