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Smog Test Emission Failure?

Tiny
PITBULLYGIRL
  • MEMBER
  • 1995 CHEVROLET BLAZER
  • 4.3L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 222,000 MILES
My truck failed the California smog test. Passed the visual and functional portion and there are no codes showing. On the smog inspection report it is high emitter profile. I must take it to a Star Station The emission test HC (PPM) results:
15mph RPM 1404 Max 62 Ave 36 Meas 89
25mph rpm 1343 Max38 Ave21 Meas 73
CO (%) results:
15mph Max 0.45 Ave 0.4 Meas19
25mph Max 0.55 Ave 0.5 Meas 0.20
NO(PPM) results:
15 mph Max 512 Ave 147 Meas 786
25 mph 536 Ave 189 Meas 513
Results: Fail
I asked the technician what would cause it to fail, and he said he did not know. In 2022 I bought it to get smog test and at that time they said my truck was equipped with the wrong catalytic converter. I was able to get a CARB Executive Order for the catalytic converter showing it is approved for my truck. I had to go through the BAR Referee to get the documentation. Now that it is not passing the smog test, I don't know what to do. A new catalytic converter costs almost $600. I do not want to spend the money if it is not what is causing the failure. The truck is running good. It had a high idle about a month ago, but I adjusted the timing and now it is correct. I replaced the distributor cap, rotor, spark plug wires and plugs approximately 3 months ago (3,000 miles ago) I changed the oil last month and replaced the air filter. I do not know what more I should do at this point. What could I check? I have been told Catclean is a good product to put in the fuel to clean things out. I have to get my fuel down to 1/8 of a tank and my tank is almost full, so it's going to be a few days until I am able to put it in my fuel tank. Any assistance is greatly appreciated. Thank you in advance.
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Friday, April 19th, 2024 AT 2:58 PM

35 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,747 POSTS
Hi,

High hydrocarbon readings can be caused by several things. Often, it is the result of an incomplete burning of fuel. If the engine isn't reaching operating temperature, dirty air filter or air restrictions to the throttle body, worn spark plugs, a rich air/fuel mixture, excessive fuel due to a failing fuel pressure regulator, or even a faulty engine coolant temperature sensor can cause the fuel mixture to be too rich and lead to higher HC.

So, where do we start? When was the last tune-up? Have you checked the fuel pump pressure to make sure it is within the manufacturer's pressure specifications?

Start with this. First, confirm there are no restrictions between the air filter and throttle body. If that is good, check the fuel pump pressure.

Here is a link that explains how to test it?

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

I attached the manufacturer's pressure specifications below. You will need a fuel pressure gauge to do this, but most parts stores lend one to you.

Let me know what you find.

Take care,

Joe

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Friday, April 19th, 2024 AT 8:55 PM
Tiny
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Hi Joe,

Thank you for your quick response. The last tune up was approximately 3 months ago. I will confirm there are no restrictions between the air filter and throttle body, and I will check the fuel pump pressure tomorrow and then let you know the results.
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Saturday, April 20th, 2024 AT 1:45 AM
Tiny
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  • MECHANIC
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Hi,

You are very welcome. Let me know if there is anything I can do to help. Also, let me know the results. I'm interested in knowing.

Take care,

Joe
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Saturday, April 20th, 2024 AT 9:59 PM
Tiny
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Here is more information: There are no restrictions between the air filter and the throttle body. Fuel pump pressure is 54 psi, not running. It has good compression, cylinders are as follows: # 1/170, #2/170, #3/170, #4/180, #5/170 and #6/175. I installed a new harmonic balancer, air conditioning compressor and the serpentine belt a month ago. Timing is where it is supposed to be. The brown and black wire under the passenger side dash was disconnected when I checked the timing as the manual says to do and has been reconnected. The engine has good spark, the plugs are gapped at 45, In my opinion, they look normal for an emission equipped vehicle, they look lean. I put a vacuum gauge on the truck and it's running in the normal range. The truck's idle is really rough though. It revs high while I am driving. The idle when waiting at a red light, revs up unexpectedly at times, eager to leap forward. It catches me off guard. No current trouble codes showing, but recently the code 35 for high idle came up a few times. What else can I check? I'm stumped.
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Saturday, April 20th, 2024 AT 10:09 PM
Tiny
JACOBANDNICKOLAS
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Hi,

The issue appears to be related to the idle air control valve. If you look below, I attached the diagnostics related to the code (35).

Take a look through the diagnostics and let me know if you are comfortable performing them.

Take care,

Joe

See pics below.
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Saturday, April 20th, 2024 AT 11:11 PM
Tiny
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  • MEMBER
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I forgot to mention there was an inside fuel line leaking about 5 months ago. I replaced both lines inside the engine. Could that have caused damage to the catalytic converter? I'm going to put Catclean in my fuel tank as soon as I get the level down to approximately 1/8th tank and see if that works to help remove carbon that may be in the engine and clogging components. Any suggestions where to go from here? Thanks
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Saturday, April 20th, 2024 AT 11:13 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

I don't feel the fuel lines would have caused the issue. The next thing I would check is to see if the catalytic converter is working. The temperature of the exhaust leaving the converter should be hotter than when it enters.

Here is a link that explains how to check it:

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

Check that and let me know what you find.

Joe
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Sunday, April 21st, 2024 AT 5:55 PM
Tiny
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Hi Joe,

I appreciate how much help you are giving to me. In your previous message you asked if I am comfortable performing some of the diagnostics you provided. I am comfortable doing most things, but I use an Autoxray Code Scout 2500, it is not a scan tool. I was lucky to find something that works on my truck. Since my Blazer is a 1995, it's a 1.5, so finding a scan tool that works on my truck is difficult. I will check out the link you provided and let you know what I discover. Thank you.
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Sunday, April 21st, 2024 AT 11:39 PM
Tiny
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Hi,

No problem whatsoever. I just hope I can help. Let me know what you find. Also, here is a link that explains how to retrieve codes without a scan tool. Try it. It may help you.

All you will need to do this is a short jumper wire or even a paper clip.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Let me know what I can do to help.

Take care,

Joe
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Monday, April 22nd, 2024 AT 8:27 PM
Tiny
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Hi Joe, this afternoon I poured a can of Catclean in my fuel tank. I filled my gas tank up and I am going to drive it around for a couple of days and put some miles on it and see if I notice a difference in how it is running. It still has an issue with the idle revving high at times when I am parked or sitting at a red light. It doesn't happen all the time, but the idle seems off. At times when I am idling with the truck stopped or in park it feels like it's going to die and other times the idle is really high for a few seconds. I will check the catalytic converter tomorrow and follow the instructions you gave me. Thanks again. I will let you know what happens.
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Monday, April 22nd, 2024 AT 11:13 PM
Tiny
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Hi, I was trying to check the timing because it is one of the things. I read if it's off it can affect the catalytic converter. When I make the timing marks where they should be the truck won't start at all. I put the distributor cap in on compression stroke at top dead center, unplug the under-dash wires and start the truck, put timing light on it, and I can't find the timing marks. It seems to run ok. I can't see the mark on the dampener, don't know where it is at. The only way I can get the timing mark on the dampener to show up is to put it on the #4 spark plug wire and then the marks light up. It doesn't make any sense. I haven't been able to check the catalytic converter yet or do what the Catclean says to do after pouring it into my gas tank. I just barely got it running. Please tell me how to see the timing marks. My original harmonic balancer had two timing marks and one was a little bit off from the keyway and the other one was 90 degrees to the right of it and my new balancer has only one mark just a little off center of the keyway, but it is real close to it.
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Tuesday, April 23rd, 2024 AT 3:30 PM
Tiny
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It sounds like you may have the distributor installed 180 degrees off. Did you have it removed?

Let me know.

Joe
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Tuesday, April 23rd, 2024 AT 5:59 PM
Tiny
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Hi Joe,
Yes, I did remove it, but when I installed it, I made sure it was on the compression stroke.
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Wednesday, April 24th, 2024 AT 11:36 AM
Tiny
JACOBANDNICKOLAS
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Hi,

Do me a favor. Remove the distributor cap and align the timing marks on the crankshaft. Confirm the distributor rotor is pointing at cylinder 1.

Rotate the crankshaft 360 degrees until it aligns with TDC. Is the rotor pointing at the correct direction?

Let me know what happens.

Joe
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Wednesday, April 24th, 2024 AT 6:34 PM
Tiny
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Hi Joe, I did it a couple of times. Turned completely over and rotor is still pointing to cylinder #1.
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Wednesday, April 24th, 2024 AT 6:45 PM
Tiny
JACOBANDNICKOLAS
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If you mark the timing mark on the crank pulley, can you see where it is located when cylinder one lights the timing light? I always use a white grease pencil. You could use a sharpie if you have one.

Joe
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Wednesday, April 24th, 2024 AT 7:52 PM
Tiny
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No, I can't see it. The only way I can get the timing light to show the mark is when I put it on the #4 cylinder which to me, makes no sense at all.
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Wednesday, April 24th, 2024 AT 8:24 PM
Tiny
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Hi Joe, Do you know why the harmonic balancer I just bought has one timing mark and the original one had two? They are 90 degrees apart. Thanks for your help.
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Wednesday, April 24th, 2024 AT 8:43 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Unfortunately, I can't answer that. However, the single mark on the new one should be where it needs to be.

I tried looking up info to see if anything was indicated, but the only thing I found shows one. Take a look at where the keyway on the crankshaft is located. Check to see if the new one aligns with it in the correct position based on where the old one would have set.

Let me know.

Joe

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Thursday, April 25th, 2024 AT 7:06 PM
Tiny
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Hi Joe, I apologize for how long this has been taking, but I appreciate you sticking with me. I will check to see that it is in the correct position. I will let you know. Thanks.
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Thursday, April 25th, 2024 AT 11:09 PM

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