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Let's Talk California Smog

Ok, I failed my Smog Test again today.

I was able to bring my HC down by ridding the stumble on acceleration. It's close but no cigar.

1) What I did to eliminate the stumble was to remove the vacuum to the Diverter Valve, which open the valve to let air from the Smog Pump in the Exhaust. I can make it stumble by putting a vacuum pump on the Diverter Valve.

2) Since I disconnected this, I no longer am putting air into the Exhaust, which I believe is why my Nox went up.

3) I am ready to have my spare "new" Catalytic Converter Welded on since I have a feeling my Cat went bad since the car always ran very lean.

Please take a look at the Smog Test results and throw me some ideas.

This is the last PASS in 2009



This was the FAIL in June 2011



This the FAIL yesterday - Aug 2011


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1981 Porsche 928 "Euro" Auto Gunsmoke Metallic Flat - Black Interior
1983 Porsche 928S "US" Auto Light Bronze (Copper) Metallic - Brown Interior **SOLD**
Old 08-23-2011, 09:44 PM
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I cant help you on this Leo, we don't have smog check in Ohio (yet.....)
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Old 08-23-2011, 10:13 PM
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Heet
Old 08-23-2011, 10:23 PM
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Move.
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1978 Porsche 928 Euro 5spd. Silver metallic/Black
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Old 08-24-2011, 01:47 AM
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Comparing 09 to now, HC is way too high AND NO is over limit, sounds to me like the injectors aren't balanced or have bad patterns etc., some lean, some rich, not looking good for the cat either.

Maybe try and look at each or some of the legs of the exhaust header with a IR temp gun?
Old 08-24-2011, 02:03 AM
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Quote:
Originally Posted by Danglerb View Post
Comparing 09 to now, HC is way too high AND NO is over limit, sounds to me like the injectors aren't balanced or have bad patterns etc., some lean, some rich, not looking good for the cat either.

Maybe try and look at each or some of the legs of the exhaust header with a IR temp gun?
Good info. I will try the IR trick. Injectors are basically new (MB's), going to hope this is not my issue. Spark Plugs look good and normal.
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Old 08-24-2011, 05:30 AM
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The diverter valve would only cause the car to stumble if it had a vacuum leak.

Whether the smog pump is pumping air into the exhaust or diverting it out, it shouldn't cause a stumble.
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Old 08-24-2011, 12:01 PM
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Oops, I think I confused the diverter with the EGR system...check the EGR system.
Old 08-24-2011, 12:50 PM
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Quote:
Originally Posted by MrGST View Post
Oops, I think I confused the diverter with the EGR system...check the EGR system.
There is no EGR on my Car. Smog Pump pumps air to the Diverter Valve, which I believe get's diverted to the back of the Heads when vacuum is applied. Someone please correct me if I am wrong.

I need to look more at my vacuum line set up. The Diverter Valve should be connected to vacuum line that vacuums only on throttle up, correct?
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Old 08-24-2011, 03:19 PM
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Quote:
Originally Posted by rjm65 View Post
The diverter valve would only cause the car to stumble if it had a vacuum leak.

Whether the smog pump is pumping air into the exhaust or diverting it out, it shouldn't cause a stumble.
You need to come over and see what I am talking about.
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Old 08-24-2011, 03:19 PM
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I can cruise by on Sunday AM and we can go over all the vac lines.
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Old 08-24-2011, 04:25 PM
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Quote:
Originally Posted by rjm65 View Post
I can cruise by on Sunday AM and we can go over all the vac lines.
Thanks Raymond. I'll be here.
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Old 08-24-2011, 04:45 PM
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Diverter sends the air pump flow to either the cats or the air filter box. Used I think only during cold start when mixture is rich.
Old 08-24-2011, 08:32 PM
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Quote:
Originally Posted by Danglerb View Post
Diverter sends the air pump flow to either the cats or the air filter box. Used I think only during cold start when mixture is rich.
Yes, hence the hose that fits under the Air Box. Mine doesn't go directly to the Cat as some set ups. Mine goes to the Heads, I don't have that extra air tube coming out of my Cat. Does this set up act like an EGR does? I read somewhere that doing the same test on an EGR "does" stumble the engine.

I got a lot to learn about the stupid smog system. Is there a diagram for us CISers on the Smog System and routing?
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Old 08-24-2011, 09:07 PM
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Typical air injection is just "someplace" in the exhaust pre cat.

EGR is routing some exhaust back to the intake side to "I think" reduce peak burn temperatures in the cylinder that create NO when the mix is very lean.
Old 08-24-2011, 11:25 PM
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I found a Euro Vac Diagram and everything looks like mine "except" I never saw a Vacuum Control Valve" (#5) on my set up.

Also, if looking from above the engine, the 3 vacuum ports coming out of the rear of the Throttle Body (#2), looks like the center port goes both tho the Decel and Diverter Valves. The left port goes to the lower port on the WUR.

How do you check a "Check Valve" (#9)?

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Old 08-25-2011, 10:10 AM
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Quote:
Originally Posted by rjm65 View Post
The diverter valve would only cause the car to stumble if it had a vacuum leak.

Whether the smog pump is pumping air into the exhaust or diverting it out, it shouldn't cause a stumble.
Is this documented somewhere? Or did you test this on your car?
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Old 08-25-2011, 10:12 AM
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A check valve is simply a one-way valve. Hook up a mity-vac or similar and ensure that one side holds a vacuum and the other doesn't.
Old 08-25-2011, 11:15 AM
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Quote:
Originally Posted by MPDano View Post
Is this documented somewhere? Or did you test this on your car?
Blowing air into your exhaust system cannot make your car stumble. The smog pump blows air into the exhaust to aid further combustion of the unburned gas, and all of this is taking place in the exhaust. It's not like an EGR valve where you're putting exhaust back into the intake side. Now if the diverter valve is bad and it's causing a vacuum leak, then that could cause a stumble.

Valve 9 is a one way check valve, it's to keep the hot exhaust from flowing back into the diverter valve and burning it up. The check valve is back between the firewall and engine block on mine. To check, disconnect the hose between 8 and 9, when you start up the car there should be no flow coming out of 9. In fact, due to the venturi effect may actually have a little suction present, so have someone blip on the throttle to make sure you don't get any flow OUT.

In ok, out bad.

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Old 08-25-2011, 11:35 AM
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