How can I fix this problem

SHAWNALU

MEMBER
1991 CHEVROLET SILVERADO
200,000 MILES

What do I need to do to pass my truck for emissions if my HC is 133 and my NO is 1033. Ive changed my EGR valve, my vacuum isnt leaking and my timing is only advanced by 5 degrees. Prior to repairs my HC was 133 and my NO was 1030. I have an after market cat converter that is legal in the state of California.

5 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

Any codes in the computer?Did you make sure you egr valve ports wernt clogged?

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Friday, September 28th, 2012 AT 1:40 AM

SHAWNALU

MEMBER
10 POSTS

Before repairing, my timing was off by 11 degrees. Then when I went in again today it was advanced by 5 degress, do I need to replace my cap and rotor? I REALLY dont want to have to replace my cat conv. But its looking like I may have to. If my cap and rotor was bad would it throw my HC and NO readings that high? I dont have carbon in my EGR ports, I cleaned those, I changed my oil today. All that work and my smog still failed

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Friday, September 28th, 2012 AT 1:43 AM

SHAWNALU

MEMBER
10 POSTS

No codes thrown, from what ive been told if its the converter, it wouldnt throw a code. How much truth that I dont know.

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Friday, September 28th, 2012 AT 1:44 AM

SHAWNALU

MEMBER
10 POSTS

Ive heard some ideas on how to "mask' the issues so I can pass emissions but I dont want to mask it, I want to know what the issue is so I can fix I and not cause anymore issues. Im sure the person before me that owned it did some shady stuff to get it to pass but, id really like to just get the issue fixed.

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Friday, September 28th, 2012 AT 1:49 AM

SATURNTECH9

MECHANIC
30,869 POSTS

How do you really know the egr ports are clean?Did you remove the egr valve and start the engine and see if the engine races and you hear a loud exhaust leak?If you didnt you need to do that to be sure. Thats the first thing I would do as far as a code for a bad cat pre 1996 doesnt have a code for the cat.