77 280z began blowing black smoke.and missing.Idles fine for 10 seconds or so before

[crazy428z]

my 77 280z will start and idle fine...then begins missing and blowing black smoke out of exhaust.IVE REPLACED THE afm,the water temp. sensor,fuel filter,and tuned it,and I still have the same problem.this does not happen gradually,but all of a sudden,like a switch or relay kicks on.anybody out in Z land have or of had a simular problem,that might have an idea what might have went wrong? Any help would be greatly appreciatted.

[Zed Head]

Download the FSM. Run through the tests in the Engine Fuel section. You'll need an ohm-meter and a fuel pressure gauge. Without measurements it's just gambling. Measurements at the ECU connector are best.

More history on the car and engine would be good also. Did the engine run fine for ten years and start doing this or did you just buy the car and it's done this since you got it?

[Zed Head]

I just noticed that you've reposted your problems and already have a bunch of replies in another thread. It's all the same crowd...

[FastWoman]

I would bet money that you have a bad connection to your coolant temp sensor.

[grantf]

My guess is a very rich running engine. Fastwomans bet would be a possible cause. So I second that. When I was having trouble with my car one symtom was black exhaust. The temp sensor was one of of many culprets. I'm sure if you looked at the plugs they would be black also. Did you replace the AFM with a new one?

[crazy428z]

dont know what this FSM is{field service manual ?} I do have a disk from nissan that has the circuit tests using 35 pin connecter.Thats how I ended up replacing AFM.I should go through it again though.As for history of car,I bought car three years ago not running and it had been sitting in a garage for two years.I got it home, went through all wiring and connecters,and replaced EFI relay,and lo and behold,she ran.Scince then,2000 dollars later, and a lot of work put in,everything relating to engine is new, including fresh rings and bearings 2000 miles ago.Shes been running top notch for ayear before Itore it down,and scince I put it back together.And about the other thread....I just touched a computer for the first time in my 48 years yesterday.Someone else even printed out the info. I needed from nissan disk on to paper for me.Anyway please understand this is all new to me. Thanx.

[Zed Head]

Wow, 48 years before you had to submit! That's impressive, as is your ability to communicate on the internet right away. The internet is a strange place, good luck with it.

You might have the Factory Service Manual (FSM) on that disk already. If not, you can down load it here - http://www.xenons30.com/reference.html

The TPS, coolant temperature sensor and the AFM are the primary sources of fuel enrichment, through the ECU. BUT, your problem does sound very similar to an ECU problem that comes up occasionally. I had a bad one that went really rich all of a sudden, then died completely, and a member here, Z Train, has also wrote about ECU problems that caused rich running. He and others have reported that they could bang on the side of the ECU and fix it temporarily. Apparently some of the old solder connections can crack and lose contact. It's a stretch but something to consider if all of the test numbers come out right.

[240260280z]

I would bet money that you have a bad connection to your coolant temp sensor.

My money is there too.

[crazy428z]

Thanx for reply,and advice.Wouldnt I get a bad reading from ohm meter when doing circuit test through ECU pin connecter,if that were the case?

[Zed Head]

I'm not really sure, I never tested mine, it was actually a spare that I was checking out. I installed it, started it up cold, drove about a mile then it died and it wouldn't start and run without choking and dying again. I swapped the original back in and put the bad one on the shelf.

Here is the thread by Z Train - http://www.classiczcars.com/forums/showthread.php?36903-280Z-ZX-ECM-tech&highlight=rich

It looks like the pictures have expired though so a little tougher to see what he was talking about.

[FastWoman]

Crazy, yes, you would get a bad reading, but only if you are smart about how you catch it. What you should do is to make sure the black smoke is coming out of your tailpipe before you shut the engine down. Do not do anything else. Proceed immediately to the critical measurement: WITH THE IGNITION *OFF*, pull the ECU connector, and take your #13 pin reading. If it reads normal, plug the connector back in, and start the engine. Does the engine still blow black smoke, or does it run normally? You want to find agreement somewhere.

You can also take the other approach and clean/replace any connectors that look questionable. My own CTS and thermotime connectors were pretty crusty/crumbly. If yours look like mine did, I'd replace them anyway. The problem might go away.

The other things I'd check are the throttle position switch, the air temp sensor, the AFM, and the cold start valve. (Check the CSV to make sure it's not stuck open. Check the AFM vane to ensure it doesn't stick open, and check its connections to make sure they're good. Check its potentiometer board to be certain it's clean and in good order.) As Zed suggested, it could also be your ECU, but perhaps not as likely. Give it a few bumps/kicks to see whether that kills the black smoke.

[crazy428z]

I finally can get back to all of you that gave me advice on my 77 280z,and the rich running condition I was having.I tried tapping on ECU,and even swapping it out with another I had;with the same results.I ran a fuel pressure test and found PSI to be in mid 40"s{44 to 46 PSI}I then replaced fuel pressure regulator.I had to pull the injectors,and found one that was jammed,{maybe from excessive fuel pressure?},so I replaced them with a set that I had cleaned up.Lo and behold...she runs, and not too shabbily either.Thanks for the tips though,as they were all good advice.Now, not to abuse this new fount of info,but does anybody out there know if the vacuum advance operates on full engine vac.,or if it is reduced?The hood that is on my 77 is not the original hood,and is missing vac. diagram.