Codes PO404 and PO300, has no power, will not shift correctly and loss of speed up hills

Tiny
FORDMAN79
  • MEMBER
  • 2001 CHEVROLET MALIBU
  • 3.1L
  • V6
  • 2WD
  • AUTOMATIC
  • 114,356 MILES
Car runs fine at idle and while in park revs just fine but when in gear it does not want to move. Has no power does not want to shift unless you let off gas. Can't step more than 1/3 on pedal or loss of speed. And hills forget it, It was working just fine on way home from work parked it and next day this happens. I got a po404 code and a po300. I know it could use a tune up but never had bad plugs because of a EGR problem. Please help.
Thursday, July 15th, 2021 AT 11:07 PM

17 Replies

Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello, I'm Danny.

Here is the information you requested. Yes, the code P0404 is related to the EGR-Exhaust Gas Recirculation system. If not working properly it will act as a choke on the engine which may be like the symptom you are experiencing on your car. I've attached picture diagnostic steps below on how to test for this code on your car. Let us know what you find and we'll go from there. Hope this helps and thanks for using 2CarPros.
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Friday, July 16th, 2021 AT 2:41 AM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
The question by burky is the same thing my car is doing but I can go up hills just only at like 10 miles an hour and if at speed as soon as you start up a hill speed drops quickly.
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Friday, July 16th, 2021 AT 7:35 AM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
When going have to let off gas to shift from first gear and at no more than 20 MPH or it screams the RPMs around 3,000 and does not move. Getting codes po404 and po300.
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Friday, July 16th, 2021 AT 7:39 AM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Just to add my 2 cents, I would check the fuel pressure to be sure it is correct. Low fuel pressure will cause this and the 300 code.

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

Fuel Pressure .................... 52-59 psi

(KOEO) Key On Engine Off

I also would have the cat converter checked. If it is clogged, the engine cannot breathe and there will be little or no power.

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

https://www.2carpros.com/articles/catalytic-converter-replacement

Roy
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Friday, July 16th, 2021 AT 11:19 AM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
Well, car already had a fuel pump put in about 5 thousand miles ago or less just changed out EGR with one from my other car that has different needs but runs right and there was no change in the one I'm currently working on after changing out.
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Friday, July 16th, 2021 AT 1:50 PM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
Plus when activated by scan tool you hear the EGR move.
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Friday, July 16th, 2021 AT 1:51 PM
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
You still need to check the fuel pressure even if it was replaced Yesterday.

I am leaning more toward the catalytic converter being clogged. You could remove the cross-over pipe under the hood and start it up and drive it around and see if the power returns.

Roy
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Friday, July 16th, 2021 AT 2:21 PM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
That's what I'm working on doing now is removing the converter.
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Friday, July 16th, 2021 AT 2:26 PM
Tiny
ASEMASTER6371
  • MECHANIC
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Okay, keep us updated.

Roy
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Friday, July 16th, 2021 AT 2:38 PM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
Also while I was driving I had my scanner tool running live data and I had seen that stft and ltft were both running at a negative value ltft was like -33. Something. And I also seen that the o2 b1s2 was reading at 99.9 % what could all this be telling me?
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Friday, July 16th, 2021 AT 3:22 PM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
I know none of those readings are good or where they should be but not totally sure what is the correct readings are and what the ones I am getting tell me.
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Friday, July 16th, 2021 AT 3:25 PM
Tiny
ASEMASTER6371
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If you are driving without the catalytic converter they are not valid readings.

Do you have the catalytic converter removed? If you do, does it run better?

Roy
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Friday, July 16th, 2021 AT 3:53 PM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
That was this morning with the catalytic converter and before I swapped out the EGR.
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Friday, July 16th, 2021 AT 4:21 PM
Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello again.

Anytime you see a minus in STFT - short term fuel trim or LTFT- long term fuel trim that means you vehicles computer is removing fuel from the engine as the car is running rich. Since you were talking about the catalytic converters it is possible they could be plugged causing this drivability issue. Here are a few few tutorials showing catalytic converter symptoms, testing and replacement:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

https://www.2carpros.com/articles/catalytic-converter-replacement

Let us know what you find and keep us updated. Hope this helps and thanks again for using 2CarPros.

Danny-
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Saturday, July 17th, 2021 AT 1:22 AM
Tiny
FORDMAN79
  • MEMBER
  • 10 POSTS
Well, it ended up being a bad catalytic converter. Ended up replacing the entire exhaust system.
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Monday, July 19th, 2021 AT 8:44 PM
Tiny
ASEMASTER6371
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Good job. It had all the ear markings of a clogged converter.

Roy
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Tuesday, July 20th, 2021 AT 3:16 AM
Tiny
DANNY L
  • MECHANIC
  • 5,648 POSTS
Hello again.
Glad to hear you were able to get the problem fixed! Thanks again for using 2CarPros and we hope you will use our site again in the future when needed.

Danny-
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Tuesday, July 20th, 2021 AT 7:09 PM

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