Possible ignition control module issue

Tiny
CADE CASTLEBERRY
  • MEMBER
  • 2005 CHEVROLET IMPALA
  • 3.4L
  • 2WD
  • AUTOMATIC
  • 201,900 MILES
When I went to the mechanic shop a bit ago for a check engine light, he said it was the spark plugs so he replaced it. The cars lights had been flickering for a while and it started to have a rough idle and bad acceleration. For a week or so the problem was fixed and it ran way better but same thing came back after that. Took it back and the same code came up so he replaced the wires instead. Didn't fix anything and he said it was most likely the ignition control module. Don't know if I should trust him so I'm coming here instead.
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Monday, August 16th, 2021 AT 8:09 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

It could be the ignition control module. It is located under the ignition coils. This is something you could replace yourself. It really isn't too hard of a job. However, if you have the diagnostic trouble codes that were pulled, let me know what they are so I can confirm a couple of things.

Here is what I suggest: Remove the module and take it to a parts store. Many stores have the ability to test this component. Have it tested. If it's good, then reinstall it. If it's bad, then replace it. Keep in mind, it could be a coil also. That is why I need to know the codes. There are three coils. Each one provides spark to two cylinders at the same time. If you have two cylinders with a misfire that function from the same coil, I would think it's a coil.

If you look at the pics below, I provided the directions for the removal and replacement of the module. Make sure to pay attention to which spark plug goes to which coil. They must be replaced in the exact positions they are removed from.

Also, let me know if you notice any strange odors from the exhaust. If you ran the vehicle for an extended period of time with a misfire, there could be a problem with the catalytic converter.

Let me know what you find or if there is anything I can do to help.

Take care,

Joe
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Monday, August 16th, 2021 AT 9:50 PM
Tiny
CADE CASTLEBERRY
  • MEMBER
Just checked, says it's the o2 sensor.
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Thursday, August 19th, 2021 AT 4:24 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

What did you check? Do you mean you scanned it? If so, what code was found?

Let me know.

Joe
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Thursday, August 19th, 2021 AT 7:10 PM
Tiny
CADE CASTLEBERRY
  • MEMBER
Darn, I didn't write the code down. I used an odm or whatever the tester thing is called that you plug in under the steering wheel. It just said o2 sensor low volt or low something. I started working at a lube shop so I can check it on Friday.
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Thursday, August 19th, 2021 AT 7:32 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

No problem whatsoever. Let me know the code. There are two O2 sensors on this vehicle. One will be in the exhaust manifold and the other near the catalytic converter.

I attached pics below so you know where they are located. Pic 1 shows sensor 1 and pic 2 is sensor 2.

Take care,

Joe

See pics.
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Thursday, August 19th, 2021 AT 7:42 PM
Tiny
CADE CASTLEBERRY
  • MEMBER
Good God.
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Saturday, August 21st, 2021 AT 5:55 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

The first thing that caught my eye was a lean fuel mixture. That can be causing several different issues, including the random misfires.

There are a couple of things that can cause a lean mixture. The most common is an engine vacuum leak. Also, a weak fuel pump can be the cause as well.

Do this first. Check to see if there are any vacuum leaks. Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If you don't find any leaks, then I need you to check fuel pressure. Here is a link that explains how it's done:

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

I suspect the lean fuel mixture is causing the problems. That is a theory at this point. I can tell you that an ignition control module won't cause a lean fuel mixture.

Let me know what you find. Note that the O2 sensor readings can be a result of the mixture as well. I attached the manufacturer's fuel pressure specifications below.

Take care. Let me know if I can help.

Joe

See pic below.

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Saturday, August 21st, 2021 AT 7:18 PM

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