Engine rough running - at wits end

[JSM]

Those look pretty dark for only 15 min of run time. The boot from the AFM to TB doesn't have any tears in it? Can you post a pic of the engine when you get a min? 

Edited March 1, 2017 by JSM

[the_tool_man]

8 minutes ago, JSM said:

Those look pretty dark for only 15 min of run time. The boot from the AFM to TB doesn't have any tears in it? Can you post a pic of the engine when you get a min? 

The boot looks like practically like new.  No tears.  All the soot has made me think it's running rich.  But the popping in the intake has everyone telling me it's running lean.  I don't know what to believe.

Photo of boot right after I got the car.  I've replaced the coil and plug wires since this photo was taken.  So disregard the beat up coil wire.

 

Edited March 1, 2017 by the_tool_man

[JSM]

Plugs don't lie! You have an overall pic? I have one AFM and the car runs perfect. I have another and it pops through the AFM. 

[the_tool_man]

24 minutes ago, JSM said:

Plugs don't lie! You have an overall pic? I have one AFM and the car runs perfect. I have another and it pops through the AFM. 

I have lots of pics. The only overall engine photo is from the day I bought the car (below).  The coil of wire around the AFM was what I stuck in it to hold the flap open and let the car run well enough to drive it off the trailer and into my shop, lol.  That AFM ended up having an intermittent fuel pump contact, and had been "adjusted" by someone.  I replaced it with a known good one from a running car.  I've included a couple of closer shots of the sides of the engine in case they help.  I've got close-ups of just about everything.  So just ask if you want more detail.

[siteunseen]

That looks really clean!  I'm hoping you figure out your gremlins soon. 8^)

 

What's the loop of wires around the afm*

Edited March 1, 2017 by siteunseen

[JSM]

Have you gone through all the checks in the FSM section EF-18 through EF-24 (Engine Fuel):

http://www.nicoclub.com/manuals/280z/1977/77_datsun_280z.pdf

if you down load this PDF, this starts on page 100. 

[Zed Head]

Are those irridium plugs?  And what's the gap?  It looks wide in your pictures.  77 doesn't have high-energy ignition, and uses about.032", not the .040" later systems used.

Still not sure what, exactly, the issue is.  It's not clear if you're just working on idle behavior or if you drive ti and it has problems.

The 6th plug seems white.  Could be you're running on 5 cylinders.

[the_tool_man]

Just now, Zed Head said:

Are those irridium plugs?  And what's the gap?  It looks wide in your pictures.  77 doesn't have high-energy ignition, and uses about.032", not the .040" later systems used.

Still not sure what, exactly, the issue is.  It's not clear if you're just working on idle behavior or if you drive ti and it has problems.

The 6th plug seems white.  Could be you're running on 5 cylinders.

Good idea.  I'll check the plug gaps.  I still have the old, conventional plugs, though they're really dirty.  I could swap those back in if you think they'd be better.

Once again, the car will start and idle, albeit roughly, when cold.  Once warm, it won't really idle for very long, maybe 15 seconds or so.  At any temperature, when I attempt to rev the engine, it will hesitate and pop a few times in the intake.  Then it will rev.  If I hold it at 2000 rpm or more, it seems to run pretty smoothly, with a slight tremble.  I don't know if that's normal or not, since I've never owned one of these before.  I have not attempted to drive the car, other than driving it off the trailer and into my shop.  The driveway is very steep.  And the thought of trying to back it up that hill with it sputtering and dying doesn't appeal to me.

I verified spark on all six cylinders with my timing light.

[Dave WM]

load test the white plug cylinder. See if that one is dead by pulling that plug wire off with car idling, does it change it idle, it should.

make sure you have the correct plugs, with the correct gap, correct heat range, use new ones, try again and note if they look carbon fouled.

for over rich check fuel mix which is what it looks like, check water temp sensor AT THE ECU resistance, compare to chart in the FSM for correct reading given water temps.

CONFIRM operation of CSV (pull it out and check for leaking)

check Air filter to make sure its not clogged, seems like the AFM would deal with this but what the heck.

check fuel pressure regulator, confirm pressure 36 psi engine not running but pump on (pull starter solenoid wire and turn ign key to start, read pressure).

check pressure again with engine running, should be somewhere near 30 psi.

Reseat the ECU 35 pin connector. when all else fails (all sensors are reading right at the 35 pin, and reseating does not help and you have eliminated ALL other possibilities like fuel pressure/CSV, then consider the ECU itself.

 

hopefully no one has monkeyed with the AFM settings.

 

 

 

 

 

Edited March 1, 2017 by Dave WM

[Dave WM]

back to a dead cylinder (if you find one that fails the load test), since you have checked for spark, next check for fuel, start with a stethoscope and listen to the fuel injector, should hear it clicking away, compare to the others. If you have a dead cylinder and you have compression and spark, then it pretty much has to be fuel. If the injector passes the click test, next up would be to pull it and do a flow test. But don't do any of this without conducting the load test 1st.

[Zed Head]

45 minutes ago, the_tool_man said:

At any temperature, when I attempt to rev the engine, it will hesitate and pop a few times in the intake.  Then it will rev.  If I hold it at 2000 rpm or more, it seems to run pretty smoothly, with a slight tremble. 

Went back through the previous pages and searched for "pressure".  I don't see a verified fuel pressure reading.  You have a lean plug, a rough running engine, in a car that might have sat for a while.  You've replaced some parts but haven't verified that specs. are right.  I'd get a fuel pressure reading before spending too much time on anything else.  You need to know the number.

Your dilemma is typical.  You're working on the easy surface items, but you really need to verify the essentials.  Fuel pressure is critical for electronic fuel injection systems.

[the_tool_man]

10 hours ago, Dave WM said:

load test the white plug cylinder. See if that one is dead by pulling that plug wire off with car idling, does it change it idle, it should.

make sure you have the correct plugs, with the correct gap, correct heat range, use new ones, try again and note if they look carbon fouled.

for over rich check fuel mix which is what it looks like, check water temp sensor AT THE ECU resistance, compare to chart in the FSM for correct reading given water temps.

CONFIRM operation of CSV (pull it out and check for leaking)

check Air filter to make sure its not clogged, seems like the AFM would deal with this but what the heck.

check fuel pressure regulator, confirm pressure 36 psi engine not running but pump on (pull starter solenoid wire and turn ign key to start, read pressure).

check pressure again with engine running, should be somewhere near 30 psi.

Reseat the ECU 35 pin connector. when all else fails (all sensors are reading right at the 35 pin, and reseating does not help and you have eliminated ALL other possibilities like fuel pressure/CSV, then consider the ECU itself.

hopefully no one has monkeyed with the AFM settings

Load test is a good idea.  I'll try that.  Plugs are new with correct heat range.  I'll check gap.  Water temp circuit has been verified.  I will test CSV.  Air filter was removed on day one.  FPR has been replaced.  Fuel pressure was good.  Leakdown was in spec.  Fuel check valve tested good.  AFM came from running car.