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Check engine light continues to turn on?

Tiny
LSAPOPE
  • MEMBER
  • 1998 VOLVO S70
  • AUTOMATIC
  • 228,000 MILES
Check engine light continues to go on despite the following:

1. New plugs.
2. New battery.
3. New fuel injectors.
4. New Distributor cap and rotor (no new wires yet).

The car will run smoothly after each repair until it is rough again after a few days or so. It sometimes will stall out. It sometimes will have a rough sound too.

They can’t seem to find out the source of the problem. The vehicle is always maintained properly and regularly.

Help... I’m going down the rabbit hole trying to find a solution.
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Thursday, January 4th, 2024 AT 8:07 PM

16 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

By chance, do you know what diagnostic trouble codes are stored when the light turns on? Has the fuel pressure been checked to confirm it is within the manufacturer's specifications?

You have done a lot already. Has anyone checked engine compression?

Sorry for so many questions. Let me know as much as you can and the codes if you have them,

Let me know.

Joe
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Thursday, January 4th, 2024 AT 9:06 PM
Tiny
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Thanks Joe. I don’t know that info but I’m bringing it back in on Monday. One of the invoices says “code for multiple misfires” thus the plugs, distributer cap and rotor replacement. I’ll ask on Monday if they’ve tried the engine compression. If you think of anything else, please let me know.
Thank you.

Linda
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Thursday, January 4th, 2024 AT 9:33 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Linda,

Also, ask if the fuel pressure was checked and the engine coolant temperature sensor. If possible, let me know what codes are found.

Take care and let me know if I can help in any way.

Joe
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Friday, January 5th, 2024 AT 10:59 PM
Tiny
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Thank you, Joe. I will let you know.
I did find some notes from one of the mechanics and this is what it said:
453, 543,451,454 and 455 - all the misfire codes. I’m going to ask them to note all codes from now on. That will be helpful.

Have a good evening.

Linda
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Saturday, January 6th, 2024 AT 1:32 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

If those are P codes, none of them are related to a misfire. I was able to find three of them and they are all related to the fuel tank pressure sensor. Take a look below. Note: P0454 and P0543 are not listed for this vehicle as a P-code, but I know 454 and 543 aren't misfire codes.

Let me know.

Take care,

Joe

See pic below.
Image (Click to make bigger)
Thumb
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Saturday, January 6th, 2024 AT 9:20 PM
Tiny
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Okay. I’ll discuss it on Monday and show them.

Thank you.
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Saturday, January 6th, 2024 AT 9:32 PM
Tiny
LSAPOPE
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Turns out yes, they were P codes. They checked the fuel pressure and leaks. They’re in the process of checking for computer issues. Could it be related to electrical issues? Any other ideas. I shared your input with them today and they are delving further for answers with another tech in the local area with experience, too. It’s a community effort now.
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Tuesday, January 9th, 2024 AT 10:17 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

Absolutely, it could be an electrical issue or a sensor issue. What I find interesting is that after each repair, it ran well for a while and then started over again. I have a feeling; it could be a fuel pressure issue.

When you speak with them again, ask if they can check the short-term fuel trims on live data and let me know what they tell you.

Let me know.

Joe
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Tuesday, January 9th, 2024 AT 8:21 PM
Tiny
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Okay. Will do.
It’s so frustrating.
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Tuesday, January 9th, 2024 AT 10:32 PM
Tiny
LSAPOPE
  • MEMBER
  • 11 POSTS
They said yes they checked that. He said it came back with a #1 rating.
If it’s a pressure issue, what does that entail? Are we talking an engine issue? Does this require a new engine? This engine has 227,000 miles on it and is a 1998 S70 turbo. Up until now it’s been a great car.
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Saturday, January 13th, 2024 AT 7:55 PM
Tiny
JACOBANDNICKOLAS
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Hi,

The engine has a lot of miles, but because it works good for a time after the repairs, I don't feel the engine is the problem. I still feel it is a fuel pressure issue.

Were you able to determine what the codes 454 and 543 were? Was there a typo in your original post?

The idea that the only relevant codes are related to the fuel tank pressure sensor leads me to feel that is where the problem is coming from. I could be wrong, but that is where I would be spending my time. Let me know about the two mystery codes. Maybe something will help with them.

Something just clicked in my mind. The P0543 is related to an intake air heater. That could be causing issues. I attached diagnostics below. See if this is something they checked as well. I'm not sure why the code isn't listed for this vehicle, but the symptoms are there. It's a theory. See what they say.

Take care,

Joe

See pics below.
Images (Click to make bigger)
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Saturday, January 13th, 2024 AT 8:50 PM
Tiny
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If what you say is the real issue, what can resolve this?
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Saturday, January 13th, 2024 AT 9:19 PM
Tiny
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What kind of cost is involved?
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Saturday, January 13th, 2024 AT 9:25 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Hi,

I would need to determine the cause of the failure. It shouldn't be too expensive. Let me know if this is something they can check for you.

As far as difficulty, it should be attached to the air filter box. There is a thermostat that will pull a flap in different directions. One direction allows outside air to enter and the opposite direction allows heated air to enter.

Let me know.

Joe
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Sunday, January 14th, 2024 AT 6:46 PM
Tiny
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Will do.
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Sunday, January 14th, 2024 AT 7:11 PM
Tiny
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Thank you.
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Sunday, January 14th, 2024 AT 7:11 PM

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