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

@siteunseen thank you for the help! I have some good news for today

 

So I decided to just swap the AFM as a future investment for the car. It had been tampered with previously before I got the car, so I had no idea where the OEM specs were for the cog. Picked it up from zcarsource about 20 minutes from my house.

Slapped it in and WHAM nothin, though it may have ran just a tad better. I also bench tested it, and the specs were a little closer to the online manual's. @siteunseen You were right though, the 150ohm didn't matter.

I pinched the return line briefly and it started leaks all over the fuel rail showering a highly pressured mist, so that with the pressure test confirmed the fuel pressure is solid. Also good to note I have a new pressure regulator.

I hadn't timed the car since the first start, and after fixing all the vacuum leaks it had me wondering. So while the car was running I moved the distributor and wellah! Idled much better (was still popping out the intake) and I could actually free rev it. It seemed like it wanted more, so i pulled the bolt out and twisted it past the little mount it had. Here, it ran even better, although when the car is warm it still stumbles at idle. However, it now free revs as I imagine the car should, and sounds healthier. So, what could this mean? Should I do some tests on the dizzy like if the vacuum advance works and such. Educate me, cause I am an idiot. So far my best theory is that somehow I messed up the mechanical timing and the ignition timing is compensating. Now that fuel and vacuum and the EFI system is set, its a matter of timing this puppy.

When running the timing light I could see that it was off of the pulley indicator and was reading somewhere in the negatives.

Here is a photo of what the dizzy is set to temporarily. We are close to settling this engines demons once and for all.

 

 

 

I have mine at full advance and it runs fine. By that I mean loosened the bolt and turned it all the way clockwise. Fyi, I'm not any kind of trained mechanic just seat of the pants and what sounds good to my ears. You seem curious to figure it out which is good in my opinion.

No worries, you are still a huge help. I am just a college kid with a dream and set of tools so🙃. I am pretty much wondering why I need to push the distributor past the stock adjustment plate to get it to run right. I know the timing is off, but I don't know why it is off so much. Even at that point it still stumbles a little bit, the engine is just 1000% happier running like that then it was before at 10deg btdc like the sticker on the hood recommended. 

Remember, when you check the timing with a light, to get a accurate reading, you need to disable the distributors vacuum advance.  Unplug its vacuum line and cap it so you don't have a leak.

There should be another bolt on the distributor that faces downward. It will add a little more adjustment range. It's possible the distributor quill is not exactly in the right place.

Or the plugs wires aren't in the normal locations

I did not know that the vacuum advance was supposed to be capped. Great tip, thank you. Which bolt are you referring to? I checked all around and all I could find were the two mounting bolts and the adjustment bolt. In addition I checked my firing order, all looked good there!

I stand corrected. I am praying that this might rest the demons once and for all. I had the firing order different, adjusted after the following photo I attached. Is this wrong? If it is I wonder how the hell this car ran enough to even try and idle. 

 

Now that I look at it though, the order seems the same, the distributor just seems rotated on one of the photos. Correct me if I am wrong

Edited May 14, 20213 yr by ckurtz2
I noticed something

Look for the vertical line molded in the cap. That's #1.

 

http://atlanticz.ca/zclub/techtips/distributor/correction.jpg

 

 

Edited May 14, 20213 yr by siteunseen

Actually, not trying to one-up anyone, but the vacuum advance on the Z's is ported vacuum.  So it's closed at idle, no vacuum.  But, if you have the vacuum advance hose on the wrong port you might get full vacuum advance at idle.  Which would screw up your timing light reading and your idle timing.  I'd hook up the light, then remove the vacuum hose.  If timing changes the hose is on the wrong port.

If you're still not sure of firing order and timing, then set your damper pulley mark at zero to ten and remove the distributor cap.  The rotor should be pointing at whatever terminal is "number 1".  Move your number one wire to that terminal and check your timing again.  If things are screwed up then you might have a problem with your damper. 

Make sure you know where you started so you can at least get back there if things don't work.

The two pieces of metal that slide to adjust timing.  One is bolted to the bottom of the upper part of the distributor. That bolt should be in a slotted hole

Hey guys thanks for the tips. I found that other adjustment screw and it helped give me lots more range. The firing order, distributor allignment, etc are all correct. I decided to swap the spark plugs, because the old ones were fouled from my AFM "diagnosing". Anyhow, she runs much better, especially when cold.

A few things to note, it takes a long time to start (I am thinking that the fuel pressure bleeds off) and it runs much better when cold. However when warm there is a very clear missfire happening and very, very occasional pops out the intake, but the new spark plugs mostly fixed that. It just sounds like its stumbling. I have done tons of little tricks and tests to rule out spark, which is completely fine. I also believe the timing is almost good, as I have the distributor set where it runs best. Now the missfire and stumbling baffles me, but I have some questions.

First, I reppined the fuel injector connectors for new ones and I am worried that I have every single connector exactly backwards. What I mean by that is that the two wires were swapped potentially. Would this affect how the injector fires. Online has many different opinions as they are just "solenoids" and will work no matter what. Other people say that if they are backwards they may fire out of phase. 

Second, does it matter which injector connector goes where. I remember reading somewhere that it didn't matter on these old z cars.

Last of all, I was wondering if someone could test their own car with the ignition on, and see which port in your injector connector is the switched positive and which is ground. That way I can determine if mine are backwards.

We are so close to correcting all the millions of mistakes I made on this car originally, I see the endzone.