o2 sensor

The short terms may be adjusting for the change to keep the long term at 0.

Roy

i didn't notice any difference after changing fuel pump also fuel filter checked.

The short terms are always moving to keep the long terms at 0.

Roy

so what do you think now? what else remain to check? fuel pump changed but nothing changed
i remember before i have this problem my long term was about +8 but i will also mentioned that, it was when i have a cold air intake. now it is run on stock air filter.

What about the EGR?

Roy

I don't have EGR system in my car.

You said you removed the catalytic converters? Is that correct?

Roy

yes, but not completely. i mean i didn't remove. someone cleaned the materials inside catalytic converters. after that because off check engine light i used o2 sensor spacer and after that p0430 only comes up sometimes I mean once in 3 months.i didn't have any problem after removing catalytic converters and performance and acceleration was awesome for a while but now i don't now what it is.

Did you ever give me the compression checks?

Roy

No comparison test have been done and it was about 200 or 201 for almost all cylinders.
i want to mention two things;
sometime when i accelerate hard i can smell exhaust inside cabin but there is no smoke coming from exhaust
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.

The only other thing I can think of is a volume check on the fuel pump to the rail.

You have covered everything else.

My gut still tells me it is mechanical in nature.

Roy

how can i check fuel volume?

As i changed fuel pump today and it doesn't affect any thing in good way. do you think it still can be a problem? or fuel volume is a separate thing?

Remove the line to the rail and use a hose to direct it to a bucket. then turn on the key and watch the flow. See if there is any air in the flow.

Roy

Thanks man. i will redo everything for make sure nothing missed.

i forgot to tell you one 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.

Okay, still the same feelings.

Roy

hi again, i have been searching last week to fine a clue.
what i find was my charging circuit problem because when i turn on my car battery voltage shows about 13 volt and if i turn on lights it goes down to 12.7 or near that so i suspect my alternator and did a voltage drop test.
voltage drop on positive side of my alternator and battery was 1.2 volt.
that's too much because manual says it should be less than 0.2.
i think it's wiring or connections problem but do you think it can explain my acceleration problem?

Clean the connections at the battery and alternator. Retest when done. If the reading does not change then replace the wire from the battery to the alternator and retest.

I do not believe that is the issue but low voltage does strange things.

Roy

cleaning connections make battery voltage to go above 14 while idling but didn't any good effect on cars performance.
tonight i noticed that i have a very slight hesitation at about 3,000 rpm when accelerating.

The charging system will not affect the engine performance.

Do you have a vacuum gauge to check idle vacuum to see if it is timing related?

The other thing is injectors. Have you had them cleaned?

Roy

i have checked timing myself and it wasn't off even by one tooth.
injectors were removed and cleaned recently and also i have used a bottle of injector cleaner about thousand miles ago but that doesn't help either.
i have checked their resistance too from what manual says they are all good .

Okay, I would still check the vacuum.

Roy

i don't have one and also doubt that any dealer near here have one either but can you explain me what's the point of this test? is there another way to test it?

Engine vacuum is key to engine operation. It can tell you the condition of the internals of the engine. A low vacuum will cause performance issues. Fluctuating vacuum indicates a valve issue and is also a test for cat converters being clogged.

Yes, they should have vacuum gauges in their possession. It is a basic diagnostic tool for any performance issue.

Roy

i don't know what to do more but don't you think if it was low vacuum problem it would show on fuel trims?i don't know what kind of problems could cause slow acceleration and slight hesitation and on other hand don't affect fuel trims. i think every problem like this should effect fuel trims but it didn't and also not even a misfire or any other codes.

Timing is what I am still concerned with. That is why I am asking about engine vacuum.

Roy

timing checked twice and I'm completely sure it's not timing problem.

Okay, I am out of ideas at this time. Let me review.

Roy

thanks, i will wait for you.

The only other thing I can think of is to call the dealer and see if there are any calibration updates for your PCM. There may be or did have an update for this issue.

Roy

i will be thankful if you can do that for me.

You need to call the service department near you. Give them your complete VIN number and have them check for you.

Roy

i have been busy for a while. i have changed my crankshaft position sensor after that the slight hesitation is gone but the wired thing that happened a lot of time for me happened today too. car acceleration was usual and gas tank was near empty. then i fill gas tank with only 10 liter of gasoline and after start engine acceleration was awesome but just for about 5 kilometers then goes back to usual. i don't know what it is.

You still need to do the testing I requested.

Roy

tiburon acceleration problem no code
finally i can say acceleration problem solved completely after purge valve replaced
so after replace o2 sensor
crankshaft position sensor
and finally purge valve
everything about hesitation or acceleration problem is solved
tiburon acceleration problem no cel
i hope someone use this thread in future and don't get stuck for about a year without any clue when there is no cel or code or fuel pressure problem.thank you ASEMASTER6371 for helping me
tiburon intermittent acceleration problem

You are welcome.

Always glad to help.

Roy