Hey guys,

       back again to solve another mystery on my 1977 280z California spec coupe. So in short my number 1 cylinder doesn't fire (I have no idea how long it has been like this). Or if it does it is extremely weak.  Anyways, the reason I know this is that when I pull the spark plug wire the engine idle does not change noticeably.  Also the idle is slightly rough and will surge if I have it anywhere lower than 1000rpm, as well as the car doesn't like full throttle under load. I have also disconnected the fuel injector and that made no change at idle. Disconnected any other cylinder causes the idle to drop very noticeably. 

So, here are the tests I have run thus far.

First I checked for spark in a number of ways. 

• I pulled the #1 plug and had it zap the valve cover by cranking the engine over. worked fine, spark looked strong.
• I swapped plug wires just for the heck of it between #1 and #2. No change. Dead cylinder did not follow the wire
• I swapped spark plugs from cylinder #1 to #2 and vice versa. The dead cylinder did not follow the plug. Always dead on cylinder #1.

Next checked compression

• Even between #1 and #2 at 150psi. Didn't bother with the rest.
• Pulled valve cover and turned over motor. Valves opening and closing as should. The wipe pattern on the rockers looked very good.

Next I went to the fuel injector. Which is where I get confused.

• I listened for injector noise with a screwdriver. I swear I heard a 'tick tick tick' like all the others. However, I still heard that noise when disconnected. Possibly the sound from another injector is carrying through the fuel rail.
• Tested injector for ohms. It passed matching all other injectors.
• Next I checked the connector. It was fudged up, but I would get 12v with ignition on. Measured with a multimeter with  1 pin in the injector connector and the other pin in the injector connector and going to a ground on the intake manifold. Thus is is getting current. 
  • Just to be safe I rewired a new connector on. Tested perfect.
• Removed #1 fuel injector 
  • Tested with 12v batt very briefly to see if the solenoid would actuate. It did.
  • it also was not clogged and would spray fuel.
• Checked fuel rail for fuel coming out of #1 injector rail port. Worked perfect with starter signal disconnected and fuel pump on. So no clogs there. Gas looked crystal clear.
• Replaced #1 fuel injector
  • At this point might as well try. It did not help.
• Disconnected both #1 and #2 injectors while car was running. RPM dropped
  • Swapped #2 injector plug to #1 injector. No change in rpm.
  • Swapped #1 injector plug to #2 injector. It improved rpm.
    • however I did this test many times, and sometimes the rpm would not climb. It is not consistant.

So, what the heck is going on here. Is it possible that the ECM is for whatever reason not alternating the ground for cylinder #1? Or is it possible that the #1 injector is firing but angled somehow and completely missing the spark plug. I would like to emphasize that during this process I would check plug #1 consistently and I never noticed it really appear wet. As well as it appearance never changed in general. All the other cylinders have more carbon on them as they are running a bit rich right now. 

Any suggestions are welcomed, thank you!

 

 

 

Edited April 1, 20222 yr by ckurtz2

I missed it, thanks.  77 is an odd year.  So, they kept the ballast resistor, which is a current-adjusting device, and opened the gap for the plugs.  So it's the intermediate step between 76 and 78.  76 had the same setup but a smaller gap.  Electronic module with ballast.

Who knows.  I thought there might be an advantage to a more modern module.  In the big scheme it just means he's still stuck with plug fouling, probably from the cam.  Oh well.

 

76 was pretty primitive despite the new electronic ignition.  Get the sand blaster out.

I think you have the chronology right. 74 through 76 used a smaller plug gap (presumably matched to the spark energy) and then in 77 they redesigned the module and increased the gap width (again, presumably matched to the spark energy).

Then in 78, they changed things again, but the plug gap stayed the same. (.039 - .043). They did, however, do away with the ballast resistor, so there could potentially be a hotter spark if you used a 78 module. I have dug into both, but don't remember the details of what I found inside the 78. I have pics, but don't remember the circuit details without checking my notes.

78 guts:

Oh, and I do have to say that as much as I like talking about dissecting and analyzing electronic goodies, I don't think this (ignition module chatter) has anything to do with ckurtz2 issues.

Edited April 8, 20222 yr by Captain Obvious

1 minute ago, Captain Obvious said:

Oh, and I do have to say that as much as I like talking about dissecting and analyzing electronic goodies, I don't think this (ignition module chatter) has anything to do with ckurtz2 issues.

It was a potential solution to the fouling plugs.

On 4/1/2022 at 4:01 PM, ckurtz2 said:

Now, I was super intrigued by your post as it would make sense. However, I remember playing with the idle enrichment screw on the AFM to see what was happening if the motor was lean or not. Lets just say I fouled some plugs whoops. But here was cylinder 1 compared to #2, Which I think pretty accurately confirms no boom🔥 is happening in #1:(

 

On 4/5/2022 at 4:41 PM, ckurtz2 said:

 HAH!, my tuning shop is Chuck from Sakura in AZ. I don't think any fancy computers or anything will be used, just the ole noggin. This is my first Z that has never quite run right, and they know a lot more about how Zs are supposed to look/run etc, and have a lot more experience in troubleshooting than I do. If I never get it quite perfect, so be it, but I want to get as close as possible. As long as it doesn't hurt the engine and is daily driveable, I can always swap to a different EMS later (with my track record with the EFI system on this car so far, it is seeming O so likely. I don't want to throw in the bag yet though).

It will be interesting to see what he comes up with.  I think he likes the later ECM's with NISTUNE.   @cgsheen1

Anyway, it's been an interesting discussion.  I learned something about the 77's.  Good luck.

 

Lol, love to see the discussion, nice to learn something new:) 

Replaced plugs (gapped to 0.04), cylinder 5 came back to life. Ran waaay better, but it would still surge a little bit and miss. So I think that my whole electrical problem was fixed. Ended up being a loose plug at the dropping resistor, and spark plugs. Go figure, sometimes the most complicated of issues are quite simple. The new plugs are starting to already carbon foul again. So my plan is to replace the connections at the WT sensor.

     The vacuum sits at around 15.5hg so I think having it vacuum tested will be a very smart thing to do. And if it doesn't climb to something better, than another solution will have to be figured out. I think the main reason those plugs are fouling is due to the fuel pressure being too high (low vacuum means the fuel pressure climbs significantly:(. Maybe an interesting solution will be a fuel rail with a different fuel pressure regulator. Who knows at this point, time will tell. 

 

8 hours ago, ckurtz2 said:

Lol, love to see the discussion, nice to learn something new:) 

Replaced plugs (gapped to 0.04), cylinder 5 came back to life. Ran waaay better, but it would still surge a little bit and miss. So I think that my whole electrical problem was fixed. Ended up being a loose plug at the dropping resistor, and spark plugs. Go figure, sometimes the most complicated of issues are quite simple. The new plugs are starting to already carbon foul again. So my plan is to replace the connections at the WT sensor.

     The vacuum sits at around 15.5hg so I think having it vacuum tested will be a very smart thing to do. And if it doesn't climb to something better, than another solution will have to be figured out. I think the main reason those plugs are fouling is due to the fuel pressure being too high (low vacuum means the fuel pressure climbs significantly:(. Maybe an interesting solution will be a fuel rail with a different fuel pressure regulator. Who knows at this point, time will tell. 

 

vacuum will be effected by warm vs cold engine and ign timing as well. 

      Yeah, I think my problem is all in the cam now. Here's a little update. Cleaned up tons of grounds today, and replaced several connectors as well. Once warmed up it idles way better than a few days ago, but still not quite right. Shakes and you can hear a miss every once and a while out the exhaust. Took it for a test drive, and it felt the best it ever has. About at quarter throttle it pulls pretty nice, sounds like all 6 are firing, and feels smooth overall. All of the problems I have noticed are at idle or WOT. So I tested WOT a few different ways. I put it at WOT at around 2100 rpm, no stumbling and it would pull harder and harder until about 3100 rpm and then miss to all hell. I then started from around 2000 rpm to about 3600 rpm at a quarter throttle and it didn't seem to miss at all. I then tried WOT after getting it to around 3200 rpm using a quarter throttle, didn't like that.(Note: I don't want to try things higher in rpm, because the cam is still technically breaking in). 

      Ok, cool. Figured this would happen. So I pulled plugs and yep all the ground electrodes are white as day and the outer edges of the plugs all have a little bit of black soot. So my visual diagnosis is rich at idle and waay lean under load and higher rpms. This will be the baseline, hopefully this issue will be able to be worked out with some tweaking. I also want to mention I had the potentiometer on and cranked about 1/4 of the way. Didn't want to toy with the AFM... not yet.  

     

Excellent. Clean and tight connections are your friend. And yes... It sounds like your issues are first order related to the cam now. Hope you can get that tuned in!

Do you have an air/fuel ratio meter, or are you doing this all old school?

@Captain Obvious I think it is gonna have to be some old school fun (not fun) haha. I just need it to run well enough to where it doesn't bobble at idle as much and can actually work at WOT so I can have some fun while not hurting the motor. Depending on how good it works, then I will either hold out on a new EFI stuff for a few years, or next semester. Time will tell I guess. Just having a really hard time wanting to dump even more money into this car when it still has a crabby interior and I haven't even been able to drive on public roads. I've also been considering just swapping back to the original cam, but I'd rather get this one to work.