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The engine is running rough without check engine light?

Tiny
JUJU201731
  • MEMBER
  • 2011 KIA SOUL
  • 70,000 MILES
Sometimes the car feels normal, sometimes the car does not feel good. I've been driving like this for over a year and check engine light never comes on. Problems seem to come and go

The problems are as follows:

The very first moment of pressing the gas pedal isn't smooth. Engine feeling slightly louder and rough. Engine Feeling slightly weaker. Slight drop in mpg. Car makes a hiccup when stepping on brake. Engine hiccup seems little more noticeable when making right turn. RPMs continue to stay high for a moment after the gas pedal release. Either the engine wants to rush or is slow car feels different after filling up gas (either better or worse) Power steering feels stiff once in a while. Previous Mechanic did spark plug, wire, fuel injector, Throttle body.

Possible source of problems?
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Friday, October 14th, 2022 AT 7:43 PM

12 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
I have seen the ignition coil cause this problem and not cause a check engine light. Get a quality replacement part. Here is the location of the coil in the images below.
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Saturday, October 15th, 2022 AT 2:20 PM
Tiny
JUJU201731
  • MEMBER
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If the car feels different after filling up gas wouldn't that mean, it's likely related to fuel system.
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Saturday, October 15th, 2022 AT 3:32 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
That can be, a weak fuel pump can cause that, we can confirm the problem if we do a fuel pressure test. This guide fan helps and you can get a fuel pump pressure gauge from the auto parts store and rent it for free or cheaply.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Fuel Pressure Test
Start the engine and measure the fuel pressure at idle.

Fuel Pressure .................... 338 - 348 kPa (3.45 - 3.55 kgf/cm2, 49.0 - 50.5 psi)

Let me know what you find please.
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Sunday, October 16th, 2022 AT 2:09 PM
Tiny
JUJU201731
  • MEMBER
  • 28 POSTS
So, if it's a weak fuel pump do, I just need to replace the pump?
Occasionally I noticed the car tends to feel better with improved MPG after tank fill up.
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Sunday, October 16th, 2022 AT 3:43 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Yep, it is under the rear seat which is nice here is how to change the pump out, please get a high-quality replacement part to help the repair go trouble free. Check out the images (below). Please let us know what happens.
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Monday, October 17th, 2022 AT 11:26 AM
Tiny
JUJU201731
  • MEMBER
  • 28 POSTS
Besides fuel pump and ignition coil do you have any other suspect?
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Monday, October 17th, 2022 AT 9:34 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
The fuel pump is your best chance. Let me know.
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Tuesday, October 18th, 2022 AT 10:44 AM
Tiny
JUJU201731
  • MEMBER
  • 28 POSTS
I was told by my previous Mechanic to fill up my tank about half with premium gas and see what happens and I notice problem improved. Does this indicate that problem is likely related fuel pump?
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Wednesday, October 19th, 2022 AT 3:33 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Yes.
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Thursday, October 20th, 2022 AT 11:22 AM
Tiny
JUJU201731
  • MEMBER
  • 28 POSTS
I haven't fixed my car yet due to lack of time.
I really want to make sure the fuel pump is the problem before I proceed.
Few more questions I would like to ask.

Once in a while, the radio shuts off on its own during driving and comes back on.

Fan sometimes blow cool air with A/C off.

After filling up with premium gas,
i noticed 2 thing.S

1. Engine problem improved
2. Starter motor is too powerful

and today I just noticed car has no electricity at all.
(battery is not the problem)
occasionally power comes back on but quickly goes out.
I'm unable to start car.

Is this really fuel pump?

I appreciate your help.
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Saturday, November 5th, 2022 AT 9:14 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 48,363 POSTS
Hmm, it may not be a fuel pump problem after all. We should run the codes to see what comes up.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Is the battery in good shape fairly new? Let me know what codes come back please.
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Monday, November 7th, 2022 AT 11:07 AM
Tiny
JUJU201731
  • MEMBER
  • 28 POSTS
It was just a drained battery. I didn't think the battery would be a problem because it's very new. I guess that was a separate problem.

Anyway, as for the engine problem, what I do know is that premium gas improves the problem. Some say it's bad gas pump. Some say its dirty gas tank. I don't know who to trust. Are you certain its a pump problem? Can you give me some explanation?
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Friday, November 11th, 2022 AT 4:04 PM

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