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Failing smog after new engine install.

colbystephens

colbystephens

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I'm just barely failing smog with my new engine, and my trip permit expires today. I'm nearly done with the engine break-in phase. The results indicate that I'm running a bit rich, so I think that's the most likely culprit.

How do I adjust the air/fuel mixture on my 5.7L TBI?
 
With chip burning. :(

Is this not an "exact duplicate" replacement?

Under what conditions are you failing? Accelerating/heavy load or idle it's not likely to pass without chip mods if that is where it is running rich.

You've done a very good job inspecting for vacuum leaks? Plugs/wires/cap/rotor, exhaust leak(s) are where you'd be looking for things outside of issues with fueling due to different volumetric efficiency.
 
how old is the cat? Did you get it good and hot before it was tested?
 
If you've got an adjustable fuel pressure reg you could turn it down.


Also if they dont do a visual pulling the air cleaner usually will work too. If they do visual then you could deliberately cause a small vacuum leak. That will lean things out a tad.

O and believe it or not that guaranteed to pass **** does actually work for the sniffer test. When I worked at advance that was the general advise for anything pre 96. A bottle of that and pull the air cleaner element out.
 
Adding 2-3 bottles of isopropanol dry gas to less than 1/4 of a tank has got many of my engines to pass the sniffer test when they failed on the first attempt--its another way of leaning the fuel mix ..getting the engine HOT is critical too--if your forced to sit in the parking lot with it idling more than a few minutes,your chances of it passing is greatly reduced..
 
dyeager535 said:
With chip burning. :(

Is this not an "exact duplicate" replacement?

Under what conditions are you failing? Accelerating/heavy load or idle it's not likely to pass without chip mods if that is where it is running rich.

You've done a very good job inspecting for vacuum leaks? Plugs/wires/cap/rotor, exhaust leak(s) are where you'd be looking for things outside of issues with fueling due to different volumetric efficiency.
Click to expand...

It is an exact replacement. Kind of. I guess it's a newer block, but it's a stock replacement. I probably have some vacuum leak - my cruise control isn't working, and my vac hoses are old.

The rest of your list checks off real good.

skunked said:
how old is the cat? Did you get it good and hot before it was tested?
Click to expand...

Cat is only 4 years old, but it ran behind an engine that burned a TON of oil. So, condition is a bit unknown.

Stomis said:
If you've got an adjustable fuel pressure reg you could turn it down.


Also if they dont do a visual pulling the air cleaner usually will work too. If they do visual then you could deliberately cause a small vacuum leak. That will lean things out a tad.

O and believe it or not that guaranteed to pass **** does actually work for the sniffer test. When I worked at advance that was the general advise for anything pre 96. A bottle of that and pull the air cleaner element out.
Click to expand...

They don't do a visual. I may try that guaranteed to pass stuff tomorrow though, as it's my last day on the current trip permit.

I sat in an enormous line today and idled for at least 20 minutes. That was really irritating.
 
colbystephens said:
It is an exact replacement. Kind of. I guess it's a newer block, but it's a stock replacement. I probably have some vacuum leak - my cruise control isn't working, and my vac hoses are old.

The rest of your list checks off real good.



Cat is only 4 years old, but it ran behind an engine that burned a TON of oil. So, condition is a bit unknown.



They don't do a visual. I may try that guaranteed to pass stuff tomorrow though, as it's my last day on the current trip permit.

I sat in an enormous line today and idled for at least 20 minutes. That was really irritating.
Click to expand...


Id seriously get a new cat. My k5 had a older, but great looking cat on it, failed smog...then I put a new cat on and passed. it was a bolt in from walker. I got it off rockauto for $150.

Oil burners and engines that have been down a cylinder are notorious for killing catalytic convertors.
 
colbystephens said:
It is an exact replacement. Kind of. I guess it's a newer block, but it's a stock replacement. I probably have some vacuum leak - my cruise control isn't working, and my vac hoses are old.

The rest of your list checks off real good.



Cat is only 4 years old, but it ran behind an engine that burned a TON of oil. So, condition is a bit unknown.



They don't do a visual. I may try that guaranteed to pass stuff tomorrow though, as it's my last day on the current trip permit.

I sat in an enormous line today and idled for at least 20 minutes. That was really irritating.
Click to expand...

Pull the cleaner and throw some of that stuff in and you should make out alright.
 
wetoolowdingbangow said:
Id seriously get a new cat. My k5 had a older, but great looking cat on it, failed smog...then I put a new cat on and passed. it was a bolt in from walker. I got it off rockauto for $150.

Oil burners and engines that have been down a cylinder are notorious for killing catalytic convertors.
Click to expand...

How does the bolt-in work? I cut mine out, then use glorified hose clamps to attach it to my exhaust?
 
Get that thing as hot as you can, and try to show up when you won't wait in line.

Having that cat hot will help a lot.
 
you need at least a few days for the "guaranteed to pass" stuff... not just dump it in and go.. supposed to run a tank of that thru, than reg gas...

it does work tho, got a few questionable cars thru with that stuff...
 
colbystephens said:
I'm on the verge of passing, so I think you're right.
Click to expand...

How did it work out for you? I'm in the exact same situation right now. Brand new crate 350, new cat, new injectors, stock setup, just barely failing. F'n California...
 
Do you Cali guys have to run a factory air cleaner assembly?
 
I use an open and throw the stock on for smog.
 
I dont believe you can get an open element filter and pass smog. The reason for that is theres that stupid tube that comes off the exhaust manifold which is connected to the air intake/charge temp sensor. I highly doubt this would fail you as far as numbers go but if inspected youd fail. Youd also have to go to a smog guy who understands what is supposed to be under the hood to get called out on that.
 
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