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Zed Head

Emissions saga and a home test for idle setting/tuning tip

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I just got my car checked for emissions again so that I can renew my tags.  We're on a two year cycle here so that gives plenty of time to mess around and get it screwed up .  I had my car running greatly and went straight to the emissions check station without doing anything to help it pass.  It failed, of course, so I spent the next few hours dinking around with the idle air bypass and my fuel pressure and failed three more times.  So I went home and realized that I was using my MSA AFM that I had bought new nine+ years ago and that it had always run rich.  I don't know why, it just does.  No matter how far I back out the idle air bypass I couldn't get it to lean out.  I pondered drilling out the bypass passage to let more air past the blade but it's not an easy operation.  So I pulled my last old AFM down from the shelf, an original 75/76 AFM, and installed it.  Then I leaned out the idle air bypass until removing the oil filler cap caused it to stumble to barely running.  I went back to the test center the next day and passed on the first shot through.

I realized as I was tuning that I could remove my oil filler cap and the engine would not stumble, when I had bad results.  I had forgotten about that basic "running rich" test.  Even though it was not noticeably rich, it wouldn't pass, and I could leave the cap off with no problems.

Anyway, the short story is that if you can remove your oil filler cap and your 280Z doesn't notice, you're probably going to fail the idle emissions test.  So that's the tuning tip.  If you're in CA with the 2500 RPM requirement the same test might still help.

And even though I could leave the filler cap off, it still only failed CO.  Not HC.  It was very close.

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13 minutes ago, Zed Head said:

MSA AFM that I had bought new nine+ years ago and that it had always run rich

I have one that runs rich(er) from MSA also. I don't use it though. I forget were I got the one I am currently using. I have one that is adjusted to pass smog with. I swap it out for one that my 280 likes until it's time for emissions testing.

We have rolling dyno tests done here. One at 15 mph and one at 25 mph. Along with the idle test.

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I sent you one a couple of years ago.  I was wishing I hadn't yesterday.    But the one I had left did the job.  I'm going to leave it on and the MSA will be my emergency AFM, on the shelf.

I wonder how they set those reman AFM's.  Maybe they have the wrong calibration settings at Fuel Injection Corp.  I was told that the FIC remans had a thicker and more durable carbon trace.  But it doesn't help much if they won't pass emissions.

Not clear if they actually run air through them or just set mechanical settings and assume that they will work right.

https://fuelinjectioncorp.com/products/air-flow-meters/

@Joseph@TheZStore

@James@TheZStore

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3 minutes ago, Zed Head said:

I sent you one a couple of years ago.

That's what I thought. But I still don't pass with it either and I didn't want to mess with it. The 280 likes it.

And that's funny, I wonder if the one I tweak to pass emissions is an MSA one. 

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3 hours ago, rcb280z said:

And that's funny, I wonder if the one I tweak to pass emissions is an MSA one. 

That would be good to know.  Should have the blue Fuel Injection Corp. sticker on it.  No Nissan stickers.

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Any chance you could check the label on your other AFM?  I'm curious.  I notified the MSA guys, thinking that we had two rich MSA AFM's.

@rcb280z

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21 hours ago, Zed Head said:

I had forgotten about that basic "running rich" test.

You're welcome! 🤣

screaming at TV.jpeg

Edited by mbz

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On 4/5/2019 at 12:43 PM, Zed Head said:

Any chance you could check the label on your other AFM?  I'm curious.  I notified the MSA guys, thinking that we had two rich MSA AFM's.

@rcb280z

Sorry for late response, just getting back into town.

There is no label on it.

On 4/4/2019 at 9:09 PM, Zed Head said:

Should have the blue Fuel Injection Corp. sticker on it. 

Neither of the 2 AFM's I bought from MSA have any type of identification.

I will verify as soon as I can.

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Okay, I was thinking of a different AFM Zed Head. So ignore previous post.

The one from MSA does have a label. A31-604-000 on the box and AFM.

 

afm1.jpg

afm2.jpg

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1 hour ago, rcb280z said:

Okay, I was thinking of a different AFM Zed Head. So ignore previous post.

The one from MSA does have a label. A31-604-000 on the box and AFM.

But does it run rich?

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2 hours ago, Zed Head said:

But does it run rich?

Yes

I've been in it to adj. the clock spring CW to lean it a little. IIRC about 2 teeth is all it needed.

Edited by rcb280z
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Thanks, good for everyone to know.  Maybe I'll send Fuel Injection Corp. an email if I get time.  I've never liked that AFM for passing emissions, it's never worked, except for when I had the original set of clogged injectors on my car.  It worked great otherwise but might also explain my typical 18-19 mpg.

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$193 to test! Please tell me that covers as many times as you want for a week or so?

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It's the DEQ fee plus the registration renewal fee, good for two years.  It all happens at the DEQ facility and you get as many trips through as you need to get it to pass.  Very convenient.

They even have a camera so you can get an idea of how busy they are.

Closed today.

https://www.oregon.gov/deq/Vehicle-Inspection/Pages/Sunset-Hillsboro-Station.aspx

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On 4/4/2019 at 5:10 PM, Zed Head said:

I sent you one a couple of years ago.  I was wishing I hadn't yesterday.    But the one I had left did the job.  I'm going to leave it on and the MSA will be my emergency AFM, on the shelf.

I wonder how they set those reman AFM's.  Maybe they have the wrong calibration settings at Fuel Injection Corp.  I was told that the FIC remans had a thicker and more durable carbon trace.  But it doesn't help much if they won't pass emissions.

Not clear if they actually run air through them or just set mechanical settings and assume that they will work right.

https://fuelinjectioncorp.com/products/air-flow-meters/

@Joseph@TheZStore

@James@TheZStore

Sorry for leaving this waiting so long. We wanted to give Fuel Injection Corporation a chance to respond to us about it first. James is tied up dealing with some orders, so I am jumping in for him with what little we have to respond with.

First, know that Air Flow Meters that many years old were done by our previous rebuilders here in Southern California. That company had been bought out by Fuel Injection Corporation, but the same people kept doing the work in the SoCal location for all of our rebuilds (i.e. why your AFM has a FIC sticker on it instead of a "Bret Instruments" sticker). Then, Fuel Injection Corporation took over all the rebuild work a few years ago. So how that particular one was set might have been different than what FIC does now.

As far as Fuel Injection Corporation, they did say that their claimed warranty return rate is less than 5%, and the actual warranty rate is about 2% on that model. FIC is the only rebuilder we know of that does a total tear down when rebuilding, inspecting everything at the component level. All worn or defective parts are replaced. Rebuilt units are reassembled from tested components; and to answer one of the questions you posted, all units are then tested on their in house flow bench and calibrated to O.E. specs. All units also carry an 18 month unlimited mile warranty.

So we're confident they are doing things right. Even still, they told me they are going to re-emphasize with the air flow department to keep paying close attention to the exactness of the idle settings.

Also, I'm sure you guys know this, but others who may read this may not: Greg also reminded me that the early L-Jetronic systems were just hyper-sensitive to so many things. Boot clamps not sealing completely or pinholes in the boots can throw the whole thing off. The cleanliness of the connections can do the same. Even missing insulation on part of a wire can cause an "inherited" signal from somewhere else and mess things up. So all of that needs to be checked as part of any AFM fix and adjustment.

All that applied to your specific situation, where the previous one did adjust leaner, does seem to say that yours may have worn or been damaged somehow. You've had it for 9 years and said it always seemed to run rich, but is this the first time it failed to pass? It is unfortunately 7 1/2 years beyond warranty coverage, and there may or may not be something in the settings FIC could tell you about which could set the adjustment back in a proper range or not (beyond normal "adjustments" obviously). I'm sure they would be more than willing to talk to you about it (you stated you might email them).

If you do, let us know what happens. If you do decide you have to get another rebuilt one in the future, hopefully some of this will give you at least a little more confidence.

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19 minutes ago, Joseph@TheZStore said:

All that applied to your specific situation, where the previous one did adjust leaner, does seem to say that yours may have worn or been damaged somehow. You've had it for 9 years and said it always seemed to run rich, but is this the first time it failed to pass?

No, it always failed over the years, or required tricks like lowering the fuel pressure to well below the spec. That's how I passed the first time.  If I had everything in spec, and tried to use the FIC AFM it would fail.  I like the way it ran on the engine, very smooth operation and good performance, one reason I never complained or tried to return it.  So I would put it back on after emissions, then try to pass emissions again two years later and every time I've had to remove it and reinstall an older one.   No damage, it's like new. 

It just runs richer.  I notice that the spring action of the vane is different also, with the Nissan unit next to the FIC unit.

I'll send FIC a message if get a chance.  

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5 minutes ago, Zed Head said:

No, it always failed over the years, or required tricks like lowering the fuel pressure to well below the spec. That's how I passed the first time.  If I had everything in spec, and tried to use the FIC AFM it would fail.  I like the way it ran on the engine, very smooth operation and good performance, one reason I never complained or tried to return it.  So I would put it back on after emissions, then try to pass emissions again two years later and every time I've had to remove it and reinstall an older one.   No damage, it's like new. 

It just runs richer.  I notice that the spring action of the vane is different also, with the Nissan unit next to the FIC unit.

I'll send FIC a message if get a chance.  

Ahhh ok. I'll send what you said to the guys at FIC, I'm sure that will be helpful info. Hopefully you get a chance to talk to them as well, maybe they have something that could help put it in the range where you can just adjust it and not have to remove it every 2 years. But I'm sure that would be tough to do third party over a forum, so I'll just hide and watch. Thanks for bringing this to our attention.

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Sorry I didn't see this thread earlier, but through I would throw in a little more knowledge about AFM meters.

The air flow meter is a very very sensitive instrument and has several  known weakness. One of which is the temperature sensor. If this drifts the signal sent to the Control Unit will change which in turn will change the air fuel mix. And create a cascade of changes/problems.

Second the substrate, called thick film ,has resistors that will drift over time. The resistors are ruthenium dioxide (look and act like glass )when centered or fired at high temperature. The exact resistor value is trimmed with plunge cuts into the ruthenium via a laser and the value desired monitored by an ohm meter. 

This all sounds good, but the problem comes with time when cracks develop at the end of the laser cuts. In essence the cracks grow and the resistor changes value. This can be minimized if the substrate with resistors are cured and the resistor  values rechecked. This costs big $  for commercial products so they eliminate this step.  In addition, the white substrate is  alumina (aluminum oxide), very brittle and prone to cracking if not attached to a very rigid surface. One word of warning NEVER REMOVE the screws from the substrate. You will crack it. My 75 OEM AFM has a thick film substrate made by BUORNS and the one currently in my car is made by OHMIC?? 

So we have resistors and  temperature sensors that change over  time, gas which is been reformulated, and different manufactures of the resistor substrates .

My original AFM in my 75 would intermittently quit working and at the time and I had no idea what was in the AFM. I was told that it, the  AMF, was bad so it was replace. What  I discovered was that the air temp sensor was slightly out of speck. The resistor substrate is just fine. This OEM AFM always caused my engine to run rich as well as the current AMF I have on my car. What I believe is the gas has changed in CA and the AFM as adjusted for the 70-80 vintage  gas is the problem. For many years I have had  to adjust my AFM to the leaner side to get through smog testing. Nothing has changed in my AFM , but the gas has changed.

As I discovered recently  the boot between the AFM and the TB must be air tight. I struggled for days tuning a new motor only to find I had several small cracks in this boot. Once the cracks were sealed what a difference.

Ok one more thing to pass forward . The engine  water temp  sensor next to the AFM air temp sensor are the two most important parts of the FI Control Unit inputs. If either of these two items drift or change it throws everything off.  The change I speak of is a slow drift out of specification. Particular attention to their performance is key.

Well this is my 2 cents worth and I hope it helps someone trying to learn about the FI process. Also check out the enclosure.

Ron

AFM-Bosh.jpg

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