280z dies randomly while driving..

[Zed Head]

So at 4 minutes it died, then you got out and disconnected the coolant temperature sensor to restart it, then you reconnected the sensor and drove away?

This is a stretch but it sounds like it might be related to the ECU, at the coolant temperature circuit.  The ECU failures lead to either running rich and dying or just plain immediate dying.  Disconnecting the sensor stops current flow through that circuit in the ECU.  I wonder if that's the basic reason the ECU's die, the coolant sensor circuit goes bad.  I had a 78 ECU go bad, and it would restart also after it died.

If you wanted to try a weird experiment that might even keep you going for a little while, put a switch in the coolant sensor circuit.  Just run a long wire in to the cabin from each side of the bullet connectors and install a switch.  It could even be a momentary push button switch.  Then you can break the circuit as soon as it starts to die instead of stopping, getting out, and disconnecting it under the hood.  It might help you keep going and offer a clue to the real problem.

It sounded pretty good until it crapped out.

[cclxxxz]

21 minutes ago, Dave WM said:

1.1 ohms or 1.1K ohms?

 

1.1ohms or 1100 ohms.

If its 1.1k or 1100ohms then all is ok with that system, both the sensor and most likely the hookup, you can check that off as a non issue.

 

i will redo it just to be sure.. since i had my meter set at 200 .. im guessing the test isnt accurate.. will redo all of the numbers again..

 

5 minutes ago, Dave WM said:

so the Fuel pressure is good, the temp sensor is good, and the TPS is suspect, and the air temp sensor is suspect. Neither of those would account for a sudden loss of power, but would account for a chronic mixture issue (air temp) or a idle issue that was constant.

Since intermittent shut down is the real issue, I would focus on fuel or spark. Install a perm fuel pressure gauge (extreme caution here, you don't want to have a gas leak and engine fire) and the spark monitor. You are going to have to isolate the issue before any more testing. The ign switch is a extreme long shot since it typically would be a start issue and not a run issue. With the spark and fuel pressure monitored you would have to catch it next time it happens and see which of the problems it is.

and if all else fails (spark is good and fuel pressure is good) I think the FSM just points to a bad ECU, try giving it a smack (don't know if ZX has them in the same place as the Z) with your hand on the case and see if it has an effect.

 

will get an inline Fuel Pressure Gauge.. and a Spark Monitor connected asap.. 

 

i will check the exhaust downpipe.. and the egr pipe as well.. 

[cclxxxz]

7 minutes ago, Zed Head said:

So at 4 minutes it died, then you got out and disconnected the coolant temperature sensor to restart it, then you reconnected the sensor and drove away?

This is a stretch but it sounds like it might be related to the ECU, at the coolant temperature circuit.  The ECU failures lead to either running rich and dying or just plain immediate dying.  Disconnecting the sensor stops current flow through that circuit in the ECU.  I wonder if that's the basic reason the ECU's die, the coolant sensor circuit goes bad.  I had a 78 ECU go bad, and it would restart also after it died.

If you wanted to try a weird experiment that might even keep you going for a little while, put a switch in the coolant sensor circuit.  Just run a long wire in to the cabin from each side of the bullet connectors and install a switch.  It could even be a momentary push button switch.  Then you can break the circuit as soon as it starts to die instead of stopping, getting out, and disconnecting it under the hood.  It might help you keep going and offer a clue to the real problem.

It sounded pretty good until it crapped out.

Zed,

 

so when i got out.. i was just trying to wiggle the bullet connectors that usually helps the car idle better.. then short after i pulled the ignition coil wire out of the distributor and i tickled myself.. (lesson learned) but this tells me atleast i have spark from the coil.. ofcourse the car died .. i went back inside and turned the car off and then reconnected the wire from the coil to distributor..

then i went inside again and kept trying to start the car again .. once i got it to start but idling rough.. i went outside and disconnected the water temp sensor.. and this made the car idle a little better..  but theres a caveat .. when i do this trick.. i cant rev the car too much or else it would die.. so i crawled the car to work maybe around 1.5k-2.5k rpm.. shifting from 1st , 2nd and 3rd gear only .. peobably going around 25-30mph? 

 

the car does run really good when i dont have this problem.. 

 

later today after work i will take a video of the car on my way home and i can garaubtee i wouldnt have this issue..

[Zed Head]

1 hour ago, cclxxxz said:

once i got it to start but idling rough.. i went outside and disconnected the water temp sensor.. and this made the car idle a little better..  but theres a caveat .. when i do this trick.. i cant rev the car too much or else it would die.. so i crawled the car to work maybe around 1.5k-2.5k rpm.. shifting from 1st , 2nd and 3rd gear only .. peobably going around 25-30mph? 

This is another sign that something's wrong in the ECU, I think.  Most engines will go full rich, maximum temperature-based fuel enrichment, and die immediately if you disconnect the sensor. 

If you can find a spare ECU it would be worth a try.  Maybe you can borrow one.

 

[cclxxxz]

2 minutes ago, Zed Head said:

This is another sign that something's wrong in the ECU, I think.  Most engines will go full rich, maximum temperature-based fuel enrichment, and die immediately if you disconnect the sensor. 

If you can find a spare ECU it would be worth a try.  Maybe you can borrow one.

 

if i buy one is there a way of testing it if its good?

[Zed Head]

One of these -

http://datsunforum.com/efi-troubleshooting-kent-moore-j25400-analyzer/

[cclxxxz]

40 minutes ago, Zed Head said:

One of these -

http://datsunforum.com/efi-troubleshooting-kent-moore-j25400-analyzer/

itll be hard to find one i guess than buying another ecu.. haha.. 

[Zed Head]

If you know someone else with a 280Z maybe they'll let you put yours in to their car.  If the problem follows the ECU there's your answer.

People have been known to actually see the defects in their ECU's.  Burnt parts or cracked solder joints.  Might be worthwhile to remove yours and take it apart.  It's very easy to do.

[cclxxxz]

 

Hello so just a little update .. I was able to pull the 35pin ecu connector during lunch time and run some numbers.. 

so to begin with I would say its about 55-62 degrees F outside.. give or take i just looked at my phone for current outside temp and it says 60 degrees... mid day 12:30pm...

so I tested the following.. 

Air Temp Sensor: results 2.83 - 2.85  (Terminal #6 & #27)

 

Water Temp Sensor: results - 2.36 (terminal #13 & body ground)

 

Thermotime Switch: results continuity exist 58.8 ohms , CSV disconnected, terminal #27 & body ground.

Throttle Valve Switch - still fails at “idle switch check” will try to clean later today.. but passes the full throttle switch check anything greater than 34 degrees .. the ohm reading was greater than 34 degrees..

 

and heres a picture of the pipe under the egr valve and some of my exhaust manifold and downpipe.. 

 

 

so i guess i can cross out ..

 

AFM/Air Temp sensor

Water Temp Sensor

Thermotime switch

 

Known items/issues that has a problem..

TVS at idle .. 

loose bullet connectors for water temp sensor

taped up throttle body boot

lean air fuel ratio mixture

 

I also disconnected the vac hose off the FPR and its not wet .. its actually pretty dry and i had a hard time hooking it back up..

 

thanks always!

Edited February 26, 2019 by cclxxxz

[240260280]

Give the ECU a good smack the next time it dies. See if it helps... at least it will take out some of your frustration.

?

 

 

[240260280]

Can you disconnect the EGR from the top and look inside the manifold under it.  The corrosion occurs inside.

[Zed Head]

11 minutes ago, 240260280 said:

Can you disconnect the EGR from the top and look inside the manifold under it.  The corrosion occurs inside.

I think that the valve can get stuck open too.  That would have an effect.  You might just take the bolts out, lift it off and inspect it like 246 says, then make a temporary block-off plate if it's intact inside.

Beware, the bolts tend to break.