Stalling and will not go faster than 9-18 MPH, stuck in limp mode?

Tiny
STARR & ROBB
  • MEMBER
  • 2003 CADILLAC DEVILLE
  • V8
  • 2WD
  • AUTOMATIC
  • 114,618 MILES
Fixed secondary fuel injection, mass air flow
Stalling, won't go faster than 9-18 MPH.



I don't know what else to check, I have been checking YouTube videos.
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Friday, August 5th, 2022 AT 2:21 PM

13 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

Are there any diagnostic trouble codes stored? If you haven't checked for codes, start with that.

Here is a quick video showing how it's done:

https://www.youtube.com/watch?v=b2IJGfImVvw

Next, if there is no power, one of the first things that comes to mind is a plugged catalytic converter. If there is a restriction in the exhaust, this can happen.

Take a look through this and let me know if you feel it mirrors what you experience:

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

Let me know.

Joe
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Friday, August 5th, 2022 AT 9:06 PM
Tiny
STARR & ROBB
  • MEMBER
We looked at the catalytic converters, they look fine, told though check valves, how do we do that?
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Saturday, August 6th, 2022 AT 6:37 PM
Tiny
STARR & ROBB
  • MEMBER
If we look and can see through them, screens look clean so that tells me they are not clogged, right?
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Saturday, August 6th, 2022 AT 6:39 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
If you can see through them, they should be okay. The easiest thing to try is to remove an oxygen sensor upstream from the converter. If the converter is the issue, the O2 opening will allow an exit for the exhaust. It won't be perfect, but it will be enough to make a difference.

You asked a question in your first post. I'm not sure what you are referring to. You asked, ". Told tho check check valves, how do we do that?" What are we checking?

Let me know.

Joe
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Saturday, August 6th, 2022 AT 7:58 PM
Tiny
STARR & ROBB
  • MEMBER
The combination valves.
How do we know that they are bad? When we are looking at them how do we test them, what tells us they are bad? Also, the test, after we clean it, we need to calibrate, right? For the car listed above, 5 and 4.5?
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Sunday, August 7th, 2022 AT 10:06 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I am so sorry, but the only combination valve I'm familiar with is the brake system. Take a pic of what you are looking at and upload it for me to see.

Take care,

Joe
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Sunday, August 7th, 2022 AT 9:50 PM
Tiny
STARR & ROBB
  • MEMBER
Okay, some good news, switched out MAF for the third time in 3-5 months. Sounds much quieter! Got up to 35 MPH on test drive.
Think maybe O2's next to double check. Secondary fuel injection may have ruined all the previous stuff we have done lately because it was beat up. But after replaced MAF, check engine light finally turned on, yay! Now retry for codes. Anything pop up now? Po102 MAF low circuit. Wow something finally! So, is it wiring? What makes low circuit code? Wow thanks all of you for helping the past few days! So Odb2 working, going to bring it in tomorrow- hook it up, see what happens.
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Monday, August 8th, 2022 AT 8:36 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

When you have low voltage in a circuit, the most common cause is either a loose connection or corrosion at one of the connectors.

When you replaced the MAF, was the connector in good condition? Check to see if there is any corrosion on the pins or if one is pushed out or damaged.

Let me know.

Joe
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Monday, August 8th, 2022 AT 11:11 PM
Tiny
STARR & ROBB
  • MEMBER
I don't understand why 3, 4 times within 6, 7 months we had to exchange the MAF. Are they bad when we get them from the parts store? Well, switched it out again last night and major improvement. Nothing under the hood is corroded, it's really clean, checked all the fuses but going to do it again, can I check them one by one with the multi meter? Or does it have to be the 12-volt test light? Going to check for lost or damaged pins. Wouldn't that be obvious just looking at it or is it more complicated? I'll YouTube to see. So, besides fuses and the connector, what else causes "low circuit"? Thanks everyone!
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Tuesday, August 9th, 2022 AT 9:37 AM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

Yes, you can use a voltmeter rather than a test light. As far as the low voltage, that can be a faulty module, a damaged wire shorting to ground, and so on. Also, there is nothing other than inspecting the connector pins for damage. Just make sure they are not bent, pushed in, or corroded.

As far as the parts you are getting, since you had issues, try a different brand. Some of the parts we have been seeing are poorly made and faulty out of the box.

Let me know what you find.

Joe
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Tuesday, August 9th, 2022 AT 12:36 PM
Tiny
STARR & ROBB
  • MEMBER
Man, went for a quick drive last night after replacing the MAF sensor the third time in 4 months, instead of 15 MPH, got up to 35. The engine sounded smooth and quiet. Tried to test drive today, now can't go pass 5 MPH and it starts jerking, sounds bad again, bog sound came back. I feel like we have tried everything.
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Tuesday, August 9th, 2022 AT 1:48 PM
Tiny
STARR & ROBB
  • MEMBER
Been searching Google and YouTube 24/7. Been mentioning bad coil pack? Just replaced that about 6 months ago. Sounds like it's misfiring again, I think that's how this all started almost a year ago. Under warrantee so we will try this as well, I guess. This is rough I need to get back to work. Been stuck out of town all this time.
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Tuesday, August 9th, 2022 AT 5:04 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I didn't realize you were out of town. If you are feeling a misfire, it certainly could be a coil-related issue.

Let me know if that takes care of the issue.

Joe
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Tuesday, August 9th, 2022 AT 8:21 PM

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