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, 20213 yr by ckurtz2

1 hour ago, ckurtz2 said:

It is radial slop, so I can twist it about 1/4 in each way. I also can pull it further one way which I assume is the vac advance function. 

Actually that's the mechanical advance.  When you twist it the advance weights move out against the springs.

1 hour ago, ckurtz2 said:

surges when initially revving.

You should describe this in more detail.  Surging?

Ok, those are all super helpful things to know.

Here is a video from yesterday when it was at 18 deg btdc. When colder it would idle and rev almost perfectly, and then this weird issue developed once warm. You can hear when I rev it that it almost surges. It will rev up, stop, then rev up again. Essentially its super jerky. It didn't do this as much on the test drive, but I definitely noticed it bucking in first.

 

I am going to go ahead and do a hot valve adjustment. I have the car warming up now. Revs perfect cold with almost zero bobble. Warmed up a little bit and when I pumped the throttle it gave a nice intake backfire. I want to make sure it is not the valves fault. I will also take a photo of where the cam lines up at top dead center.

13 minutes ago, ckurtz2 said:

I will also take a photo of where the cam lines up at top dead center.

The engine sounds kind of "cammy".  Confirming cam timing and ignition timing will help.  I wonder if your damper is bad.  Your ignition timing might not be where you think it is.  Feels like this has been discussed, not sure.

Make sure that you pull the straight side of the timing chain tight when you set the timing mark on the damper to zero.  Get that tight then check your cam sprocket notch and groove.

Just did a valve adjustment. A lot of them had way to loose of clearance. Only one I didn't need to touch. Weird cause I already did the adjustment once. I would say it was a warm adjustment. I also agree it sounds cammy, but I don't know why. Everything seems stock under the valve cover, but I don't know how to tell if it is an aftermarket cam. In addition, sometimes it smoothes out like when cold, so it makes me think it is just missing or stumbling.

I rotated the engine clockwise carefully until I got to TDC. I have it on mark 3, so obviously the chain has wear. However, it looks like at this position the cam is advanced still. Is that ok?

This is where the crank pulley lines up and how the cam timing marks look correlated to it. 

 

Edited May 18, 20213 yr by ckurtz2

I'm not entirely sure if yours is within acceptable parameters, but this is how i understand it is supposed to look. This is taken when reassembling my motor, which seems to be running just fine. 

Most people say turning the engine over with the cam bolt is bad, and it is better to use the crank bolt, or a remote starter.  I have used the cam bolt in the past, without causing any apparent damage, but since have started using a remote starter.

1 hour ago, ckurtz2 said:

A lot of them had way to loose of clearance.

How did the cam lobes look?  Did you check the wipe pattern after installing the camshaft?  You said "reinstalled and so on", but....

Your cam is in the "after adjustment" spot, which is good.  It does indicate that your chain is worn but cam timing should be right.

 

What do you mean by wipe pattern? It definitely doesn't look amazing. There are some burn marks and light scratches to the eye, but over the finger everything feels smooth. I never did anything to the cam, just took it off and plopped it back in. 

I refired up the car.  Much quieter up front with less valve train noise. I definitely tightened it closer to the tight specs on the hot valve adjustment guide. I just let it idle and listened from the back end. The chop is erratic which leads me to believe it is not cammed. The plugs look great, except for plug number 2 and 1 which had a little bit more carbon deposits. I pulled the injector connector from cylinder 2 and I swear the car barely changed in behavior. Ran a tad worse, but not as much as the other cylinders. May just be placebo and me wanting to find the culprit though. 

So after letting it idle for a while I went to give the car about 3/4 throttle straight away. Essentially opening up the throttle body quickly to see how the car reacts. The only thing consistent I have noticed is that after sitting idling for a few minutes and I hammer the gas, there is always a pretty big missfire out the intake. This I think is the biggest clue we have thus far. 

Which leads me to believe it may be running a tad lean still? 

@Reptoid Overlords thanks for the confirmation photo! My chain is definitely stretched, but the #3 cam pulley position compensated. Mine may be running a tad more advanced then yours, but it looks to be in spec as well. I wish my cam sprocket looked as clean as yours! 😎

Ok so here is the plan. I am going to check the dizzy shaft tommorow and make sure it looks proper with the engine at TDC. Next, because my car is a 77 cali model I am going to disconnect the altitude switch under the dash and see by some miracle if that does something. After that I think it is time for the potentiometer magic to happen. 

Regarding the pot tweak, which pot should I get. I was looking online and there are so many options within the 1kohm limit I don't know which is best. In addition, do the bullet connectors have a certain size on the water temp sensor. I need to buy some connectors for the pot that match the water temp sensor's bullet connectors. Thanks for hanging with me over this tedious process thus far!

4 hours ago, ckurtz2 said:

@Reptoid Overlords thanks for the confirmation photo! My chain is definitely stretched, but the #3 cam pulley position compensated. Mine may be running a tad more advanced then yours, but it looks to be in spec as well. I wish my cam sprocket looked as clean as yours! 😎

It was only clean because it was new then.  I've never seen one at the 3 mark before, so I'm glad to get confirmation of what it's supposed to look like. You are making good progress.  I've been watching this thread, trying not to get too involved as not to potentially confuse things.   Hoping it all works out..