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thetwood

Failed CO emissions - all controls removed - where to start?

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Last year we bought a 1978 280z from a neighbor for our sons first car. It had been our neighbors sons car and had sat in her garage for the last 11 years. We've spent the last year getting it road worthy (new fuel lines, relined the tank, new suspension bushings, all new fluids and spark plugs, new tires/wheels, got the lights and blinkers working). Finally went to register and get emissions. And boy did we fail. HC at 977 (limit of 400) and CO at 7.28 (limit of 1.5). Also, the gas cap didn't seal. We knew it was likely to have problems, but seems pretty bad.

The previous owner had lived where there were no emissions tests and was a high school kid, so he did a couple of things. He replaced the exhaust with an after market (not sure of make, but it's loud). Not sure if car originally had a catalytic converter, but it doesn't have one now. Just straight back to a small muffler.

He also removed all of the Emission Control System. EGR is not hooked up. BPT and almost all hoses are gone. See picture for the little that is left.

I'm hoping for some thoughts on where to start (other than the gas cap. I can figure that one out). I'm not a car guy. Just a dad trying to help his 15 year old learn (lots of reading and youtube videos). We'll tackle about anything, but where should we start working? Thanks for the help.

 

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High HC tends to mean incomplete combustion. (Look at timing and valve adjustment.)

High CO tends to mean rich. (Among other possible problems, it could be the cold start valve supplying too much fuel.)

Make sure you have a good distributor cap, rotor, plugs and plug wires. Do a valve adjustment. Check the timing. Change the oil before testing. 

Download the FSM (link below) and look at the EF and EC sections. Check the function of the water temperature switch

If the car was originally a California model, it had a cat. A tell-tale sign is a Floor Temperature warning light on the center console.

Since you aren't being tested for NOx, don't worry about the EGR.

Search a lot around on this site. There are a lot of threads on fuel injection that might help you.

 

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You are in a bit of an unknown. Can you ask the neighbors son what he did to the engine?

The standard EFI doesn't like changes and it looks like he a played with the engine.

He has changed the fuel rail and I can not see the fuel pressure regulator. I'm sure it's not there because the vacuum ports on the manifold are all blocked off. Maybe he installed a static fpr? That will give you an overfuel issue at idle for sure. The FPR should change the line pressure so the pressure between the injector pressure and the inlet manifold remains a constant 36psi. High vacuum equals low line pressure. A static fpr will keep delivering 36psi too high for idle.

He also installed extractors. Not saying extractors are worse for economy, but not in combination with a stock ECU. These old ECU's don't handle changes all that well and can't compensate.

The unknowns are: Did he play with the AFM vane spring adjustment and is the cam still original?

He removed a lot of other stuff like CSV and AAR, but that stuff is there for cold start. If the tests are on a warm engine you won't need it.

Edited by EuroDat

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Post a picture of this.  I think it's some kind of FPR but I don't see a vacuum source as Chas said above.  One hose is straight out of the rail then that thing then returns to the tank,

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I noticed he has a gauge as well at the front of the engine. Can you tell us what the pressure is at idle and if it changes when you rev the engine?

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15 hours ago, thetwood said:

Last year we bought a 1978 280z

And boy did we fail. HC at 977 (limit of 400) and CO at 7.28 (limit of 1.5). Also, the gas cap didn't seal. We knew it was likely to have problems, but seems pretty bad.

Not sure if car originally had a catalytic converter, but it doesn't have one now. Just straight back to a small muffler.

He also removed all of the Emission Control System. EGR is not hooked up. BPT and almost all hoses are gone. See picture for the little that is left.

The numbers aren't really that bad.  It only takes a few misfires to blow them up, you're actually within simple tuning range, i think.  Are you sure it's not a 79 280ZX?  The emissions guys might have used the build date as the model year.  The AFM to manifold hose looks more ZXey than Z.  Not sure. 

There should be a sticker on the door jamb or under the hood that says "CATALYST" if it had a converter.  Look for that.

Did the visual inspection include the EGR parts?  How do you know the gas cap failed, do they test that?  Lucky for you guys though, new caps are available for the unleaded style filler necks.  Find them on the internet.

The PCV system has been disconnected also, which tends to dirty up the oil with gasoline vapors and combustion byproducts.  You can reconnect it. 

It has a lot of the "get rid of emissions junk" mods done that cause problems for people.

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Thanks to everyone for all the quick responses. Really appreciate it.

@SteveJ, thanks for the point to the right documentation. Have it now and have started reading. According the the previous owner, it had a cat and he took it off when he ditched everything else. Will look into that more.

@EuroDat, I'm getting questions to the previous owner now. Did find out that he had swapped engines completely. It's an L28, but different number (doesn't match cars VIN). Will see what he says about the AFM and Cam. 

There is a BEGI fuel regulator, but it doesn't have a vacuum line hooked up to it so I'm assuming it's not doing much. I'll look through the boxes of stuff we got with the car to see if I can find the actual model number or documentation for it to look into this more too. 

Once my son is up to help, I'll start the car up and watch the fuel pressure and get notes back to you.

@siteunseen, I've attached a better picture of the area you circled. I think it's just a spring back there.

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That's the return line back to that adjustable fuel pressure regulator by the fuel filter.  Kind of cool stuff done to this one as far as simplicity, sucks for your Son though as he tries to pass smog. :tapemouth:

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The fuel pressure regulator looks like it can be vacuum adjustable. See black plug on the top. The way it is now, it will give too much pressure and rich running at idle for sure.

The hood should have an emmisions sticker saying catalyst if its californian.

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Edited by EuroDat

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I notice a few other things now in the picture.  It has the non-webbed intake manifold which came on 75-76.  So that's a clue.  You should probably check the cam shaft to see if it's stock.  Check valve lash while you're there.  Give it a good tuneup, back to stock specs if you can get there.

Get a piece of hose and connect that FPR vacuum port while you're watching the gauge.  Don't try to do a tuneup without the vacuum hose attached and the FPR adjusting normally, the EFI system is designed around it.  It is a critical component of the system.

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13 minutes ago, Zed Head said:

I notice a few other things now in the picture.  It has the non-webbed intake manifold which came on 75-76.  So that's a clue.  You should probably check the cam shaft to see if it's stock.  Check valve lash while you're there.  Give it a good tuneup, back to stock specs if you can get there.

Get a piece of hose and connect that FPR vacuum port while you're watching the gauge.  Don't try to do a tuneup without the vacuum hose attached and the FPR adjusting normally, the EFI system is designed around it.  It is a critical component of the system.

Where does the FPR vacuum line go to? Or know where in the service manual it goes over vacuum lines? I'm paging through but haven't found yet...

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 It should go on one of the plugged ports on the driver's side intake manifold, down from the fuel injectors. Looking at the fpr though I think its plugged off too. You have fuel IN and OUT then that rubber plug up top, that's the vacuum line in my opinion.

You're missing the charcoal evap cannister too.

Any realitives in another state you could register it through? LOL

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1 hour ago, thetwood said:

Where does the FPR vacuum line go to? Or know where in the service manual it goes over vacuum lines? I'm paging through but haven't found yet...

Pretty sure it's this one, circled in red and blue.

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4 minutes ago, Zed Head said:

Pretty sure it's this one, circled in red and blue.

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Thanks. Heading to get vacuum hose and a new gas cap now. Once I hook up the FPR, should I be able to tell a difference listening to the engine at idle if it's working?

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The gauge reading will be the best thing. Should be 32 or so psi.

I'm curious as to how it will react considering how tight that thing is sealed up at idle. Once the afm opens up it's breathing but that takes some pedal.

My guess is the idle will go through the roof but I'm either right or dead wrong so it may drop?

That big phillps head with the spring is your idle adjustment. It's behind the distributor cap, towards the windshield.

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I haven't checked the discussion item by item, but my practice in situations like this is to return everything to stock. Once you're there, you know exactly what you have. Certainly everything related to PCV system, charcoal canister and tank venting needs to be returned to stock. I'm not sure whether the earlier manifold is a problem or not.

When you have it smog tested next, make sure to drive it for a half-hour or so beforehand. Cars run cleaner when they're thoroughly warmed up.

Edited by Pilgrim

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2 hours ago, thetwood said:

Once I hook up the FPR, should I be able to tell a difference listening to the engine at idle if it's working?

The fuel gauge should read a maximum of 36psi with no manifold vacuum. Test and adjust the regulator with the engine off.

To run the pump just remove the spade terminal from the starter motor and have someone hold the key in the start position. That will run the pump without cranking the engine.

Once you have done that start the engine and check the pressure. Idle should be around 32 psi. If you flip the throttle the pressure will rise close to 36psi briefly, then drop down to lower than idle pressure and return to idle pressure.

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I assume the PCV has been deactivated (based on the air filter on the top of the valve cover, Just curious, I assume the PCV tube on the engine block has been capped as well, If not it should to prevent junk from getting in there. A better fix would be to return it to function. Also when you say the engine number did not match the VIN, did you compare it to the ID plate in the engine compartment? the I prefer to say serial numbers since that is really what they are, and the SN of the engine never match the SN of the car (top of dash). The plate in the engine compartment has both vehicle SN and engine SN.

I suppose it does not matter but the AFM is turned 90 degrees out, the plug should be on the bottom.

A typical test for air fuel mix would be to remove the oil fill cap, if the starts to slow and die, then its right, if it speeds up its rich, But that only works when the PCV system is installed and working.

 

Edited by Dave WM

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oh just noticed no AAR either (kinda slow today, recovering from hurricane prepitis), that sux. must be fun to start on a cold morning. Just don't get why folks have to remove stuff.

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So maybe the fuel pressure gauge is bad (was in the car when we got it), but at idle it's sitting around 15 psi without the vacuum hooked up. With the vacuum hooked up, it's at 4 psi. I can look at replacing the gauge to see if that's indeed the problem...

In actual forward progress, I purchased and put on a new fuel cap, so at least I should pass that one.

Returning to stock seems daunting. With a swapped engine, new fuel rail and other non-stock items added in, I'm not even totally sure where to start. The Service Manual shows where things should basically be, but I'll have to read through further to see if I can really understand how to rebuild all of the missing. Then would have to start finding all the parts as well.

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33 minutes ago, Dave WM said:

oh just noticed no AAR either (kinda slow today, recovering from hurricane prepitis), that sux. must be fun to start on a cold morning. Just don't get why folks have to remove stuff.

He was a high school kid. Why do they do anything? I know my high schooler doesn't always make the best of decisions... But wish it would have been left closer to stock.

Edited by thetwood
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