Codes 42 and 45?

Tiny
S.O.L.
  • MEMBER
  • 1988 CHEVROLET 1500
  • 5.7L
  • V8
  • 2WD
  • MANUAL
  • 30,000 MILES
Engine runs rough and a knock while under load. It all started when I got gas last week as soon as I left the gas station. In neutral I can rev the motor hard, and you can barely hear the knock at high RPMs. I replaced the spark plugs (A/C Delco) and the misfire went away for 10 minutes or so but it's now skipping again. I'm pretty sure it's loading up on the left bank (1, 3, 5, 7). I'm hoping the knock is a spark knock and not a writ pin. Any help would be great. Thanks
Saturday, December 14th, 2024 AT 3:54 PM

14 Replies

Tiny
JACOBANDNICKOLAS
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Hi,

Is it possible for you to record the sound and upload it for me to hear? As far as the misfire, it could be a couple of things. Code 42 is related to the electronic spark timing. If it is off, that is what is likely causing what you hear. I attached the diagnostics below from my manual specific to this code.

Code 45 does indicate a rich fuel mixture. It could be related to the regulator. The pressure regulator is a diaphragm-operated relief valve with system-operating pressure on one side and atmospheric pressure on the other side. The function of the regulator is to maintain a constant pressure to the injectors at all times, by controlling the flow in the return line by means of a calibrated bypass.

Note: The pressure regulator on this unit is serviced as part of the fuel meter cover and should not be disassembled. If you look at the last pic below, I highlighted the regulator.

Let me know what you find.

Joe

See pics below.
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Saturday, December 14th, 2024 AT 9:47 PM
Tiny
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I cleared the codes this afternoon and made the trip a couple miles and back let it idle for approximately 5 minutes with no codes returning.
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Sunday, December 15th, 2024 AT 1:04 PM
Tiny
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Found out my collector gasket was blown out on passenger side. Not sure if this is part of the problem or not.
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Sunday, December 15th, 2024 AT 1:25 PM
Tiny
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I'm trying to upload some video but I'm having problems for some reason.
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Tuesday, December 17th, 2024 AT 3:25 PM
Tiny
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Okay, finally!
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Tuesday, December 17th, 2024 AT 4:37 PM
Tiny
JACOBANDNICKOLAS
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Hi,

If you have an exhaust leak before the catalytic converter, yes that can cause the O2 sensor to be off and cause drivability issues. Also, I did hear the noise. Is that the exhaust leak that I'm hearing?

I can't believe what nice shape that is in. If it was here in PA, there wouldn't be anything left.

If the exhaust has been modified, I don't know what was done with the oxygen sensor or converter. Let me know.

Joe
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Tuesday, December 17th, 2024 AT 7:00 PM
Tiny
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It doesn't have a cat it just has a set of flowmasters. Will a exhaust leak sound like that? And thanks Ive put a lot of time and money into it. O and it does have the O2 sensor on the driver's side manifold.
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Tuesday, December 17th, 2024 AT 10:21 PM
Tiny
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Hi,

It's hard to tell from a video, but an exhaust leak at the manifold can often sound like that. It will also be louder under a load.

I'm not certain how the O2 sensor is being used. If the computer thinks it has a lean mixture (possible exhaust leak), it will compensate by adding fuel.

Let me know. Also, let me know if it has headers.

Joe
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Thursday, December 19th, 2024 AT 5:38 PM
Tiny
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10-4.I'll replace the collector gasket and get back with you on it.
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Thursday, December 19th, 2024 AT 7:01 PM
Tiny
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Thanks for the update. Let me know how things work out for you. If I don't hear from you, I hope you have a nice Christmas.

Take care,

Joe
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Friday, December 20th, 2024 AT 7:17 PM
Tiny
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Well, I did a compression test and found out I was down to around 40 PSI on cylinders 3 and 5. I tore into it and found the gasket in the center between them burned completely into. That being said, do you think the sound I was getting was the compression escaping the two cylinders or do I need to pull the pistons out and inspect the wrist pins? And thanks for the help.
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Sunday, January 5th, 2025 AT 1:08 AM
Tiny
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Hi,

I suspect the problem is the gasket and not the rings. However, you can test to see if the rings are faulty.

You need to do a wet compression test. Basically, that means you test it dry first, record the compression, and then add about a tablespoon of motor oil into the same cylinder and try again. If the compression increases a good bit, the rings are likely faulty. If there is little to no change, they are okay.

Since you already have the head off, that test can't be done, but in most cases, you won't have only two cylinders with worn rings. They wear evenly.

Let me know if you need any help with the head. If you need torque specs or anything, I can get it for you.

Joe
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Sunday, January 5th, 2025 AT 8:55 PM
Tiny
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Yeah it was the gasket causing it all. The noise. Thanks for the help.
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Tuesday, January 14th, 2025 AT 8:01 PM
Tiny
KEN L
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JACOBANDNICKOLAS is one of our best! Glad you could get it fixed, thanks for letting us know. Please use 2CarPros anytime we are here to help.
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Friday, January 17th, 2025 AT 11:11 AM

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