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.

 

9 hours ago, thetwood said:

When we first started the project we dropped the tank, cleaned and coated the inside (don't remember with what, but it's read and rubber like). I had an inline filter after the tank, but removed it when we were struggling to get the fuel pressure up to norm. When I removed it, there was some debris in it, which I was kind of surprised by given the work we did on the tank. I was hopeful that the filter had caught anything we didn't catch relining, but maybe not.

What's the best way to check for this? I can put an inline filter in again. I can replace the regular fuel filter. Other things to do/check?

Hopefully it cured enough. The directions say until the smell is gone. A lot of radiator shops that do them bake them to speed it up. I used a leaf blower and sat mine in the sun for a week then it wasn't smelly. If you use a clear filter before the fuel rail, I like before the main one myself it's easiest, it should show trash pretty quick. 

Good luck! Reading along but can't add with these guys. They are good.

If anyone is still following this, we're back at it. After a pause and some confusion on what to do, we just decided to take a bunch apart to see what we found. After putting things back together, the car was running much better. Not sure why, but we were happy. We got new temp tags and went to fail emissions again. The good news is that we did much better than last time. CO% now passes (went from 7.28 at idle down to 1.03). The bad news is that our Hydrocarbons are still way too high (HC PPM went down from 977.6 to 931.8, but still needs to be lower than 400 so we are easily twice as high as allowed).

My son is in his high school auto tech class now and is excited to get back to work on the car and see if we can get it closer to passing. Any suggestions on how to get the HC PPM down and where we should focus?

Thanks in advance. This group has been great to us both.

 

 

Have you opened up the idle air screw on the AFM?  That's what it's for, at least for idle.  I don't know how much effect it would have on 2500 RPM.  But your numbers are actually really close I think, it might get you there.  Take note of how many turns out it is so that you don't get lost in your adjusting, and can go back to the starting point.  Then open it up until you get a miss.  Then pick a spot in between and try the test again.

Would a Wide band help in determining this? It seems if you can get the idle leaned up properly the Hcarb output would go down

16 hours ago, thetwood said:

 

The hydrocarbons are extremely high, even for an older engine.
Hydrocarbons are unburned fuel, so you need to work out if the injectors are simply delivering too much fuel, or if there is a reason why the mixture isn’t getting burned more completely.

Edited March 26, 20213 yr by Racer X

On 11/17/2019 at 5:17 PM, thetwood said:

Also, don't think my temp gauge is working correctly, as it said I never went over 120 for the entire trip... Another thing to check. Just put in a brand new temp gauge sensor, but may need to check it more now.

Did you check the coolant temperature with something besides the gauge? If you don’t have a non contact pyrometer, you could try your hand, but isn’t as precise as a pyrometer.

It could be the thermostat is stuck open. That would also cause the engine to run too rich, as the ECM would think the engine is cold and enrich the fuel mixture.

 

Here is one of my old emissions test in Oregon.  It's idle only.  What's weird about yours is that the CO is low but the HC is high.  I seem to remember that if you had incomplete combustion your CO should be high also.  I wonder if your problem is oil related and not fuel.  Maybe leaky valve seals or rings.  You might give it a good "Italian tune up" right before you go in to warm up the seals.

Fail on top, then Pass, below.  CO was the last thing i had to get tuned in, which I did by the idle air screw and lowering fuel pressure.  They change the format for the printout, sideways for a Fail, up and down for a Pass.  You can see that as I leaned things out the CO and the HC both dropped, but the HC was already okay.  HC came in first, then CO.

Or, as I think about it, the other possibility is an ignition miss.  That produces only HC since there is no combustion at all.  That actually seems more likely.  CO shows combustion that started but did not complete, HC shows no combustion.  Full combustion should convert the CO to CO2.  With an ignition miss the gasoline (HC) passes right through along with the oxygen that is supposed to combining with it.

Just thinking in print.  I'd check those plugs and plug wires.

Thanks for the responses everyone. Some good places for us to start. There was definitely a bit of sputtering at idle, so maybe there's an ignition miss we need to check.

Now I'm dealing with another issue that I need to resolve. My son wanted to get some practice driving so we took the car out last weekend. He's not great at manual transmission and this isn't he easiest to get used to. He had a couple of really, really bad starts that he didn't handle well. Lots of jerking. After the second, the car no longer will go into gear while the engine is running. If you turn the engine off, you can get it into first so we could at least get it back home, but no shifting. We're starting research and will start checking the master/slave and hope it's something there.

I suggest you start another thread about the transmission, and when you do make sure you clarify what is going on.

You can shift a manual transmission without a clutch (though not as a beginner). Race drivers tend to use the clutch only to get the car into first.

Since it will go into first with the engine off, it sounds like the transmission will still shift. It could be an issue with the master/slave cylinder or the clutch fork. The latter is rare, but they can break.

On 3/30/2021 at 9:34 AM, thetwood said:

Thanks for the responses everyone. Some good places for us to start. There was definitely a bit of sputtering at idle, so maybe there's an ignition miss we need to check.

Now I'm dealing with another issue that I need to resolve. My son wanted to get some practice driving so we took the car out last weekend. He's not great at manual transmission and this isn't he easiest to get used to. He had a couple of really, really bad starts that he didn't handle well. Lots of jerking. After the second, the car no longer will go into gear while the engine is running. If you turn the engine off, you can get it into first so we could at least get it back home, but no shifting. We're starting research and will start checking the master/slave and hope it's something there.

 

l'll bet the fluid is low in the hydraulic clutch system.  I'll bet you find it there.

A suggestion - he might do better without you in the car.  Our daughters got their intro to manual transmissions with their uncle as the instructor and I think it worked better than if my wife or I had done it.