Failed emissions again...

[AsleepKat]

This is the result before I changed out the o2 sensor and spark plugs



this is todays




The smog tech said I just have to richen it up a hair. He smogs a lot of Porsches and said that should take care of it. Is this done by the co2 adjustment with the Allen key?

[tirwin]

Assuming the tech is right, yes you use the Allen key. What year is the car? Search on adjusting the mixture. Turn in SMALL increments. You could take it to a shop with an exhaust gas analyzer and get it dialed in. (I am looking on my phone so I can't see the pic very well.)

[AsleepKat]

It's an 83. I read a bunch of threads talking about the screw and how to get to it.
I also read about reading the voltage at the oxygen sensor to set it. I have an appointment tonight, but I'll be attempting this in the morning after I do some more reading. My temp registration expires tomorrow so it would be nice to get it done tomorrow.

[jasonlee]

I notice on your sheet is says catalytic converter N/A, does that mean you don't have one?, and if so, does that mean you fail the visual? I ask as I have an 82, that i plan to register in California in the next few months.

[AsleepKat]

I just noticed that... I don't know why it says that - he looked right at it and said, "that looks like one of those piece of ***** replacement cats." lol
He was an old arab guy, really cool, said he didn't think it would pass because it stunk at idle. After we got the results, he said it stunk because of a lean misfire.

[Bob Kontak]

Check the condition of the inside of the distributor cap.

Check that the two vacuum lines are connected to the dist and the retard vacuum line is functioning - meaning has vacuum at idle.

This website indicates your mechanic might be on to something. You failed HC and NO is high. CO is low indicating is is not overly rich. Lean would cause high heat in the combustion chamber = NO high.

See sections on NO and HC as well.

What causes high CO? Rich Fuel Mixture - SmogTips.com. Failed CO Emissions. Why did my car fail the emission test for high CO emissions. What is CO. My vehicle failed the emission test for high Carbon Monoxides. Why my car produced high CO. High CO f

[Bob Kontak]

Originally Posted by AsleepKat

After we got the results, he said it stunk because of a lean misfire.

In Ohio, they won't say a thing if you fail. Probably for liability reasons.

[Noah930]

Isn't there a law that if you have spent something like $650 on trying to fix the problem (but still can't pass smog), then they give you a pass? I recall seeing a sign to that extent on the wall of the smog shop when I was there last November.

[tirwin]

Originally Posted by AsleepKat

It's an 83. I read a bunch of threads talking about the screw and how to get to it.
I also read about reading the voltage at the oxygen sensor to set it. I have an appointment tonight, but I'll be attempting this in the morning after I do some more reading. My temp registration expires tomorrow so it would be nice to get it done tomorrow.

It is hard to set the mixture just by the O2 sensor. If you have a digital voltmeter with a real duty cycle measurement function you could try to dial it in to ~40% once the engine is good and warmed up. I just beat my head against the wall on this recently. With 40% duty cycle that means the frequency valve is OPEN 60% of the time, which is a richer mixture. To do the adjustment, you need to hook up your DVM to the green/white wire in the 3-prong test port on the left hand side of the engine bay. It's usually hidden behind the fuse panel.

Without a DVM with a duty cycle function you will be shooting in the dark.

[AsleepKat]

Originally Posted by Bob Kontak

In Ohio, they won't say a thing if you fail. Probably for liability reasons.

I was recommended to go to this guy by the people that do my registration on my cars, said to make sure I gave them their card and that he would take care of me. He was a pretty nice guy. Did a little bit of diagnosing without really doing it, if that makes sense.

[AsleepKat]

Originally Posted by Bob Kontak

Check the condition of the inside of the distributor cap.

Check that the two vacuum lines are connected to the dist and the retard vacuum line is functioning - meaning has vacuum at idle.

This website indicates your mechanic might be on to something. You failed HC and NO is high. CO is low indicating is is not overly rich. Lean would cause high heat in the combustion chamber = NO high.

See sections on NO and HC as well.

What causes high CO? Rich Fuel Mixture - SmogTips.com. Failed CO Emissions. Why did my car fail the emission test for high CO emissions. What is CO. My vehicle failed the emission test for high Carbon Monoxides. Why my car produced high CO. High CO f

I know that the blue port is pinched shut. I read somewhere here on Pelican about plugging the blue line anyways... I'm assuming it's plugged for a reason that doesn't affect emissions since my dad never had a problem passing this car in Az.

[AsleepKat]

Originally Posted by tirwin

It is hard to set the mixture just by the O2 sensor. If you have a digital voltmeter with a real duty cycle measurement function you could try to dial it in to ~40% once the engine is good and warmed up. I just beat my head against the wall on this recently. With 40% duty cycle that means the frequency valve is OPEN 60% of the time, which is a richer mixture. To do the adjustment, you need to hook up your DVM to the green/white wire in the 3-prong test port on the left hand side of the engine bay. It's usually hidden behind the fuse panel.

Without a DVM with a duty cycle function you will be shooting in the dark.

I have a Fluke 75/77. I honestly don't know if it does duty cycles or not....
I'm tempted to just go up the street to the German car mechanic and see if he can hook the gas analyzer up to it. My wife doesn't want me spending a ton of money on it though because it's not my only vehicle... lol

[AsleepKat]

Just checked and I have a Fluke 77iv meter and the Fluke site says it can do duty cycle - now to figure out how.
I love this site btw - I've learned more about my car in the last 3 months of lurking than I ever thought I knew.

[tirwin]

Originally Posted by AsleepKat

I have a Fluke 75/77. I honestly don't know if it does duty cycles or not....
I'm tempted to just go up the street to the German car mechanic and see if he can hook the gas analyzer up to it. My wife doesn't want me spending a ton of money on it though because it's not my only vehicle... lol

I don't think that Fluke supports duty cycle. FWIW, I have an Innova 3340 (less than $70 on Amazon). If you need it done tomorrow then taking to a shop may be the path of least resistance.

Your wife must be in the first stage of being married to a Porsche enthusiast: denial. Luckily this is a temporary condition although it can last for an extended period of time. Eventually they stop asking how much stuff costs when boxes of parts show up on your doorstop. Anger was in there somewhere too but all I heard was blah blah blah something something something.

[tirwin]

Originally Posted by AsleepKat

Just checked and I have a Fluke 77iv meter and the Fluke site says it can do duty cycle - now to figure out how.
I love this site btw - I've learned more about my car in the last 3 months of lurking than I ever thought I knew.

Oh good!

Here's a pic of my meter. Mine has a dial setting that says "duty %". Black lead to COM jack on the meter. Connect that lead to a ground.

Not sure about your meter but on mine I have to plug the red lead into the far left jack for the duty cycle measurement (different connections for different functions). Find the 3-prong test port and hook the red lead to the green/white wire. Your meter should read a number as a percentage.

I'm going from memory and there are plenty of posts that detail the ECU modes but on cold start I think the duty cycle is 60%, then drops to default 50% after the 15°C switch triggers and then once he engine is fully warmed it the ECU switches into closed-loop mode where it varies the mixture to achieve stoichiometric based on the O2 sensor reading. On an old analog dwell meter with a needle you can see the needle swing back and forth over a range (dithering).

What you want to do is make very slight (and I do mean very slight) turns with the 3mm Allen and watch the reading. You want to get it close to 40%. I found that just the pressure of my hand pushing down made a difference in the reading on the meter so adjust, let go and monitor the change.

Just to be clear... What you are reading at the test port is a measure of how long the frequency valve is CLOSED. If there are 10 on/off cycles of the frequency valve per second and it is closed for 4 of them (40% of the time) that means it is open for 6 of them (60% of the time). The longer the valve is open, the more fuel is delivered. More fuel = richer mixture. So the higher the duty cycle reading, the leaner the mixture actually is (the ECU is trying to increase fuel flow to richer the mixture) and the lower the duty cycle reading the richer the mixture (the ECU is trying to decrease fuel flow to lean out he mixture). When my basic mixture was incorrectly set too lean, I was reading a duty cycle of 95% meaning that the ECU was trying to add the max amount of fuel to compensate and it still wasn't enough.

Hope that helps!

[AsleepKat]

Originally Posted by tirwin

I don't think that Fluke supports duty cycle. FWIW, I have an Innova 3340 (less than $70 on Amazon). If you need it done tomorrow then taking to a shop may be the path of least resistance.

Your wife must be in the first stage of being married to a Porsche enthusiast: denial. Luckily this is a temporary condition although it can last for an extended period of time. Eventually they stop asking how much stuff costs when boxes of parts show up on your doorstop. Anger was in there somewhere too but all I heard was blah blah blah something something something.

Lol, she got used to it with my money pit 450hp 240sx... hahaha. The "problem" I think she has with it now is that her Mustang is still sitting completely stock... oops! lol
You may be right too - the site said it does, but it was lumped in with the Fluke 85 - which does do duty cycle... :/

Originally Posted by tirwin

Oh good!

Here's a pic of my meter. Mine has a dial setting that says "duty %". Black lead to COM jack on the meter. Connect that lead to a ground.

Not sure about your meter but on mine I have to plug the red lead into the far left jack for the duty cycle measurement (different connections for different functions). Find the 3-prong test port and hook the red lead to the green/white wire. Your meter should read a number as a percentage.

I'm going from memory and there are plenty of posts that detail the ECU modes but on cold start I think the duty cycle is 60%, then drops to default 50% after the 15°C switch triggers and then once he engine is fully warmed it the ECU switches into closed-loop mode where it varies the mixture to achieve stoichiometric based on the O2 sensor reading. On an old analog dwell meter with a needle you can see the needle swing back and forth over a range (dithering).

What you want to do is make very slight (and I do mean very slight) turns with the 3mm Allen and watch the reading. You want to get it close to 40%. I found that just the pressure of my hand pushing down made a difference in the reading on the meter so adjust, let go and monitor the change.

Hope that helps!

I will try in the morning with mine, but like you pointed out before, it may not actually do it.

[tobluforu]

What gears did you test in?

[AsleepKat]

They're strict here - tested in 1st for the 15mph test and 2nd for the 25mph test.

And it looks like it won't get done today - way too much rain outside.

[tobluforu]

Originally Posted by AsleepKat

They're strict here - tested in 1st for the 15mph test and 2nd for the 25mph test.

And it looks like it won't get done today - way too much rain outside.

That's actually good and you can test in whatever gears you want, at least when I was in ca I could. I had a car that would not pass, high nox, tested in second and third, changed to first and second and it passed. Good luck.

[mysocal911]

Originally Posted by tirwin

Oh good!

Here's a pic of my meter. Mine has a dial setting that says "duty %". Black lead to COM jack on the meter. Connect that lead to a ground.

"Just to be clear... What you are reading at the test port is a measure of how long the frequency valve is CLOSED. If there are 10 on/off cycles of the frequency valve per second and it is closed for 4 of them (40% of the time) that means it is open for 6 of them (60% of the time).
The longer the valve is open, the more fuel is delivered. More fuel = richer mixture. "

Right, with no power applied to the frequency valve (FV), i.e. no ground signal from the
Lambda ECU pin 15, the fuel mixture is lean as the control pressure to the fuel distributor (FD)
is maximum. So the duty cycle (DC) measurement measures the percentage of time the FV
is closed (off), which is indicates a relative measure of mixture correction by the Lambda ECU.
So a DC less than 50% indicates that the ECU is attempting to richen the mixture by reducing
the control pressure. A reading of 100% minus the DC measures the average voltage applied
to the FV to open it, i.e. this assumes that the DC is measured at pin 15 of the ECU to ground.
So a DC of 95% indicates that the FV is open only 5% of the time or it only has about less
than a volt (average) applied to it to open it.

"So the higher the duty cycle reading, the leaner the mixture actually is (the ECU is trying to increase fuel flow to richer the mixture)"

A high DC indicates that the Lambda ECU is trying to lean the mixture by increasing the control
pressure, i.e. the average FV voltage across it is reduced.

"and the lower the duty cycle reading the richer the mixture (the ECU is trying to decrease fuel flow to lean out he mixture)."

A low DC indicates that the Lambda ECU is trying to richen the mixture by lower the control
pressure, i.e. the average FV voltage across it is increased.

"When my basic mixture was incorrectly set too lean, I was reading a duty cycle of 95% meaning that the ECU was trying to add the max amount of fuel to compensate and it still wasn't enough."

A DC of 95% indicates that the Lambda ECU is leaning the mixture. If the system is in
closed loop with the O2 sensor connected, it indicates that the base mixture setting at the FD
is too rich. With the O2 sensor disconnected, the DC should be set at 50%, i.e. this assumes
the CO setting has been properly set too at the FD.