1977 280z EFI Nightmare

[ckurtz2]

ey guys!

I have a 1977 280z which used to have the California specific emissions tech. I recently "refreshed" the engine after I got it. I completely redid the fuel tank and fuel system from the tank back going as far as to replace all the hoses for the vapor tank as well. 

I am just going to list off new things.

• rebuilt fuel injectos
• new fuel pressure regulator
• new fuel damper
• fuel lines
• fuel pump
• rebuilt fuel rail
• rebuilt head and new headgasket
• all new seals around the engine
• spark plugs
• rotor
• distributor cap
• plug wires
• oil pressure sender
• water temp sendor
• water pump/ radiator / fan clutch / thermostat etc
• cold air intake
• intake hoses at AFM
• vacuum lines
• new fuseable links
• new fuses inside the car under the passenger dash area
• several cleaned up grounds throughout the car

 

I also modified the EGR system by removing it, along with the BPT system. I just did this to simplify things. I also have a 6 to 1 header from MSA going back to a 2.5 in exhaust. This deleted the catalytic converter it had.  Other major change is I removed the AC. Might still be some things left over like the vacuum canister, but they aren't hooked up.

Anyways, I am positive the mechanical timing on the engine is solid. I also set the ignition timing as the sticker on the hood. I think it recommended 10degrees BTDC, could have been after tho. The car starts beautifully like a top. However, cold or warm it cannot rev the car. If I hold the gas pedal down it will slowly rise, but then it sounds terrible and won't go further. My assumption could be it is misfiring. In addition as the car heats up it will begin to stumble, buck, and eventually die.  Quite sad to watch. I would also like to mention it idles right around 850rpm. Even when cold.

So I went to troubleshooting. If I unplug the water temp sensor the car will die pretty much immediately, so I know that it is at least getting connection. I tried adjusting the idle speed and it pretty much has zero affect until i close it, and then it will choke out and die. I also tried to test vacuum. People recommended removing the oil cap and see if the engine runs worse. I did, and it made zero affect to how the engine ran. Which made me think a vacuum leak, although I can't find one for the life of me. Except that maybe I did not plug the EGR right.

Next came the AFM. I noticed that as the car warmed up I could watch the counter balance thing on the AFM begin to bobble (representing the vane itself inside bobbling). As the car got to operating temp the AFM bobbles more and more until I can see it making extreme movements to stay alive. Then the car dies. So I thought, lets help the little bugger out. So I had a friend slightly hold the AFM open so it would run a little richer. The engine immediately ran SOOO much smoother. I tested further and had him open it slightly more as I followed with my foot on the gas pedal. And the engine would rev up with it. I actually could get it to rev all the way to 6k rpm. Sometimes it took a while to get there, other times it would rev there super quick. Never would reach redline though, most likely because the mixture was still way off.  So to me this rules out that spark as an issue. But I just have no idea what it could be. I really don't know where to start. I never got to see the car start before I redid it, because it was so crusty and likely had a blown head gasket.

I actually drove the car about a quarter mile, by running the AFM about 3 cog teeth richer. Although I had what felt like 50hp. Can't say it was a great idea, but I needed a pick me up.

I will provide some photos and let me know if you see anything immediately wrong with how I hooked things up. This is my first z car and I am on that initial steep learning curve. 

I also am based in Phoenix, Arizona. If you or anyone you know would want to help I'd be happy to host. 

 

Edited March 29, 2021 by ckurtz2

[Reptoid Overlords]

I believe the hose from your valve cover needs to be behind the throttle body vane..

Also, i cant see the ground connections from the EFI wiring harness.  They should have just enough length coming out of the harness to be connected to the intake manifold.

Edited March 28, 2021 by Reptoid Overlords

[Zed Head]

Here's your other thread, in case anyone thinks they've seen this one before.  Reptoid is right, there's something off about your PCV system.  Looks like the valve cover is open to the atmosphere.  That's not good.

 

[Patcon]

Try not to create multiple threads. It becomes confusing

[ckurtz2]

Just now, Zed Head said:

Here's your other thread, in case anyone thinks they've seen this one before.  Reptoid is right, there's something off about your PCV system.  Looks like the valve cover is open to the atmosphere.  That's not good.

 

Ok, I am totally up for suggestions, I tried to just "copy" what the engine looked like before I played with it. Here's a photo before I went and started toying and refinishing things.

[ckurtz2]

31 minutes ago, Reptoid Overlords said:

I believe the hose from your valve cover needs to be behind the throttle body vane..

Also, i cant see the ground connections from the EFI wiring harness.  They should have just enough length coming out of the harness to be connected to the intake manifold.

 I believe different 280zs had different PCV setups. Not sure if mine is right, but I do have it like it was when I got the unmolested car. Like everyone says though, who knows if what the original owner had was right. Regarding the EFI ground. If you mean the two connectors that ground on the intake, I believe it is grounded. You can see it on the first image below the air regulator. 

[Zed Head]

1 hour ago, ckurtz2 said:

 

•  
• rebuilt head and new headgasket
•  

 

Who rebuilt and installed the head?  Is it the one the car came with?

Your PCV hoses look right, I couldn't see that the one in front of the AFM was an elbow.

I'm afraid you have the typical internet dilemma of assuring everyone out here that things like cam and ignition timing are "right" and don't need to be verified, yet you can't get the engine to run right.  It's hard to get too involved when you don't have verification of those important things.  No offense, but the thought that runs through your mind is "why should we believe this guy"?

Anyway, two things that come to mind are:

1. a rotten EGR passage, where the blockoff plate doesn't work because the passages themselves are rotten.  Somebody had that problem a few years ago and he had all kinds of odd problems with the way the engine ran.  I think that he might have found it by measuring intake vacuum.  It was much lower than it should have been.  You might take an intake vacuum measurement since it is a measure of how the engine is pulling iar through the manifold.  It's a clue.

2.  

 

[Zed Head]

Could also be that some valves got bent during head installation.  A cylinder pressure measurement will show that.

[Zed Head]

In short - your symptoms seem to fit an engine that is not pulling through the throttle body.  Could be pulling through the PCV system, or the EGR system, or the valves and/or pistons are not generating enough suction.  I think that explains the AFM vane not moving.  There's no air flowing through it.

[ckurtz2]

36 minutes ago, Zed Head said:

Who rebuilt and installed the head?  Is it the one the car came with?

Your PCV hoses look right, I couldn't see that the one in front of the AFM was an elbow.

I'm afraid you have the typical internet dilemma of assuring everyone out here that things like cam and ignition timing are "right" and don't need to be verified, yet you can't get the engine to run right.  It's hard to get too involved when you don't have verification of those important things.  No offense, but the thought that runs through your mind is "why should we believe this guy"?

Anyway, two things that come to mind are:

1. a rotten EGR passage, where the blockoff plate doesn't work because the passages themselves are rotten.  Somebody had that problem a few years ago and he had all kinds of odd problems with the way the engine ran.  I think that he might have found it by measuring intake vacuum.  It was much lower than it should have been.  You might take an intake vacuum measurement since it is a measure of how the engine is pulling iar through the manifold.  It's a clue.

2.  

 

I had a machine shop resurface the head, and do a valve job, and install springs. I installed the cam and rockers and such. I was super carful when installing. Made sure the engine and head were both at TDC before installing. Of course there is always room for error. I think the next step is to do a compression test for me to check that. I am at college, and go home during the weekends to work on the car, so I can get you official TDC verifications this weekend. Trans is out to fix a leaky freeze plug, so I will give the compression check at a later date. Thanks for the help so far!

[ckurtz2]

9 minutes ago, Zed Head said:

In short - your symptoms seem to fit an engine that is not pulling through the throttle body.  Could be pulling through the PCV system, or the EGR system, or the valves and/or pistons are not generating enough suction.  I think that explains the AFM vane not moving.  There's no air flowing through it.

I agree, and I will do some more detective work in the upcoming weeks to give everyone some real numbers. Here is something I noticed. Does it matter the way the PCV system is set up? I noticed through a lot of photos people doing it different ways. For example, I have mine hooked up before the throttle vane, while some images show people capping it there and setting it up like this. Essentially, the reverse of how mine is capped.

I would give everyone numbers now, but the trans is out. The freeze plug behind the block had rusted through and was leaking. Took the liberty to change to a 5speed while the trans was out.

 

[Zed Head]

Nissan changed the hose routing in 1977.  

Here's something I've found useful.  The cars on BAT all have numerous pictures and usually run like tops.

Here's a 78. (Funny though, I see that the guy left the brake fluid reservoir open.  Still got a good price.)

https://bringatrailer.com/listing/1978-datsun-280z-84/