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

24 minutes ago, Zed Head said:

I'm not sure where you're getting your specs. from.  AFM Test #2 in the 1980 EFI book says ~150 ohms, not zero.  And 60 ohms is the typical resistance of a relay solenoid so I think that those are probably right also.

Ok that's good to know. I got my specs from 280z EFI Bible . Who knows it may be wrong. The test I am talking about was the AFM #2 or 3b. I guess it says small resistance, but I am not sure what it considers small.

Also thank you @Zed Head for listening to me. I know I am posting a ton, but it is a good way for me to log what is happening as I go along, and any advice given has been super helpful.

 

In addition, I can confirm that one of the injector seals was leaking (nearest the front of the engine where I heard hissing). It had a big tear across the small o-ring. In addition, I spilt water all over the intake and let it dry before I loosened any bolts. I hoped that the water would find its way around the manifold and seep into areas where the gasket was leaking. It turns out that a large part of the intake gasket was moist where I could hear the engine hissing. Do you think it's possible the gasket is bad here? the nuts were torqued on pretty tight, so I don't think it was too loose, but I could have been wrong. I actually think it was way over torqued. Here are some photos of what I mean. On the intake itself, you can also see where fuel seepage was happening. If I over torqued things is the gasket reusable? I put it on in January as new.

 

Edited May 2, 20213 yr by ckurtz2

Actually it looks like it was sealing where it needed to seal.  Which way are you installing the yokes?  They should have the edges pointing toward the manifolds, with the nut riding on the top of the curve.

You're making progress.  Use this EFI book, it has all years through 1980 listed.  1975 was their first shot at publishing a guide so it might have errors.

 

1 minute ago, Zed Head said:

Actually it looks like it was sealing where it needed to seal.  Which way are you installing the yokes?  They should have the edges pointing toward the manifolds, with the nut riding on the top of the curve.

I had the yokes the proper way, I had to use two washers for one of the mounts though, because I was missing one on the car to begin with. Can I just reuse this same gasket and plug everything up properly torqued this time? It was new in January.

Then my big leak must have been that injector seal, praying that is was at least haha. There's not much more for me to look at for vacuum problems once everything is back together. 

Also, thank you for that guide! I am going to start using that one:)

Good progress. One layer at a time.

I wouldn't worry too much about the AFM numbers right now. I've seen a couple anomalous readings from AFM's that worked great on the car. Might not be a problem there.

I gotta admit though that with so much going on a the same time that I'm getting a little lost on what you're working on... Is there one test that is giving you trouble that you need help with? Pick one and work through it? Then move on to the next?

@Captain Obvious

Yeah sorry about that, I kind of just updated things as I went...I just went very quickly haha. Essentially, it has been narrowed down that the main cause of my motor running like crap is not electronic, however the AFM may be slightly at fault. However, with a vacuum test it showed I had 0 vac at idle. Which is confusing to say the least, but I have never used this vac gauge before. However, I also pulled several vacuum ports and tried to plug with my finger and I felt no suction, and the motor did not run worse. So it must have poor vacuum. However, I think it must have some vacuum, because when I give it throttle the AFM meter moves too. In addition, since I did those previous vacuum fixes you mentioned a long time ago I am now able to rev it. I could not do that in January. So progress is being made, no matter how small.

I heard hissing coming from where injector 1 was. I pulled off the rail and saw that the seal was ripped and not seated. Another vacuum leak right there. I also saw that many other injectors were not seated properly. Likely due to my stupidity of not greasing them before the first install. Learned my lesson:) So tomorrow that will get replaced. In addition, I removed the intake and exhaust and put them back on making sure they are torqued properly. Essentially, I am taking no **** from this car and finding every vacuum leak possible:). 

If the car still runs like marbles, well I will cry myself to sleep, burn the car to the ground, curse the heavens, or take it as a taunting from the car for a hammer. Lets hope it doesn't come to that🤠

11 minutes ago, ckurtz2 said:

take it as a taunting from the car

Now go away, or I shall taunt you a second time!   

Injectors leaking air is a big deal. Take care of that and we'll see what happens next.

          Hey guys I am back. New injector seals seated nicely. I was on a camping trip so just got back to working on the car. Anyways, fired it up, and it ran about the same, I can still hear a hissing in the same spot. The only other spot that I could imagine be leaking vacuum is the vent PCV hose from the block to the intake near the headers. I pulled it and it definitely had cracks, but looking from the inside shining a light and bending the hose it looks like none of the cracks go through. I still think it needs replacement, I just can't find one in stock. I also for the hell of it loosed the cog tension on the AFM about 4 teeth. It helped, but it still wanted more fuel, so I stopped knowing that something else is amiss.

         I had a new water temp sensor laying around so I decided to toss it in. There was a positive impact, but only marginal. So right now I am thinking a new AFM may be justified, but I am curious what you guys may think. I also redid all the engine bay wiring harness connectors, so those are now a solid connection. When revving the car I also noticed it would occasionally pop through the intake, so maybe my ignition timing is off? It is just hard to set it, because I can't keep the car to hold a steady idle when it is warm. Looking forward to hearing advice!

 

I'm sorry for not reading up the thread but something that I did once was put the valve cover gasket on upside down. There's a difference at the front and if you get it wrong it'll leave a little gap on the thermostat housing side.

Sorry again I don't know about the hissing, could be a snake up in there?

 

On 5/1/2021 at 3:44 PM, Zed Head said:

When you moved the AFM vane you were adding fuel.  Seems like a vacuum leak somewhere, or the typical "lean AFM/electronics" problem.  The "temp sensor tweak" is the cure for that.

Not sure what's going on with your voltages.  Are you sure there's not a decimal on the display?  What kind of meter?

http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html

This modification really is worth trying.  It has worked for many many 280Z owners.

The hissing might be the FPR.  They hiss as fuel squeezes through.

@siteunseen now that you mentioned it that had me thinking. Took a peep though and all looked good

@Zed Head that tweak is very intriguing, and I won't hesitate to use it as a last resort. However, for now I am trying to get the system to function as it should without any extras, but if she is too stubborn I'll just have to do it haha. 

Now, I pulled the AFM to give it a nice "bench test" instead of going through the car's wiring harness. Thought it would give a more accurate result. Everything was pretty much the same! 

However, between pins 7 and 8 I was reading 182.2. It is supposed to read "approximently 150ohm". In addition, pins 6 to 8 read exactly 182.2 (supposed to be 180 so that one checks out good). I found it interesting how both of these tests are the exact same resistance. What could that mean? What is the function of pins 7 to 8? Simply put, pins 7 to 8 have about 21.3% more resistance than it should, which isn't "approximately 150ohm". I am not afraid to put a new AFM from zcarsource on her, I just want to hear honest opinions of you think I should get it done. 

 

 

1 hour ago, ckurtz2 said:

However, for now I am trying to get the system to function as it should without any extras,

It has been proposed that either today's fuel is not the same as in the 70's, or that the electronic components in the ECU's have aged.  Either way, without a time machine your quest might be impossible.

The AFM's from MSA seem to run rich.  So one of those might get you closer.  But might cause problems if you need to pass emissions.  Good luck.

I think that I already commented on the 180 versus 150 measurement.  I don't think it matters.  "Approximately 150 ohms" just means there should be "some" resistance.

Edited May 13, 20213 yr by Zed Head
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