81 280zx N/A running rich/backfiring... Please help - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 14 (permalink) Old 04-17-2017, 10:07 AM Thread Starter
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81 280zx N/A running rich/backfiring... Please help

Any help here would be HIGHLY appreciated!!



I picked up an 81 280ZX 5 spd N/A and was told it had been sitting for about 2 years and needed a fuel pump.



I installed a new fuel pump, drained all the old gas, put new gas in and got it to start and run, but it runs like ****.



Looked under the car after it had reached normal warm temp and the catalytic convertor was glowing orange so I figured it must be stopped up so I cut it out but it didn't help it run any better.



So, I changed the oil, put a new set of properly gapped plugs in it. Runs and sounds a little better than before, but still not right.



I noticed that the SOLID RED check engine light stays on. If you give it any gas, it mostly just sputters and backfires for about 5 seconds but then it will clear up all of a sudden and rev up to 4-5k rpms and sounds like its hitting on all cylinders. (I should note that I noticed that the yellow FUEL light stays on until right as soon as I can get it to clear up from sputtering. It flashes off and the car revs right up, but backfires when going back to idle..



I have checked many switches and connections. I noticed the thermotime switch was partially broken and the connector was it terrible shape, so I replaced both but it hasn't made a difference.



I unplugged the CHTS while the engine was running and it immediately shuts the engine off. Im assuming that means that its ok...??



I found one small vacuum hose that is attached to the very rear of the intake manifold on the driver side that has been disconnected on end, but cannot tell where it originally went. Also, capping this hose with my thumb while the engine is running did nothing.



Any ideas on what I should do next? Coolant temperature sensor? The car warms up normally and does not overheat. temp gauge seems to be working fine



I listened to all the injectors with a stethoscope and they are all ticking away when the car is running.



Any advice here will be appreciated....Thanks
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post #2 of 14 (permalink) Old 04-17-2017, 10:35 AM
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FSM fuel injection section. You checked the plugs and they are carbon fouled I presume. The water temp sensor (not the gauge one, the one that tells the ECU the engine is cold) would be 1st. Its all well covered in the FSM where to start and how to check with simple tools like a VOM.
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post #3 of 14 (permalink) Old 04-17-2017, 11:08 AM Thread Starter
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Originally Posted by Dave M View Post
FSM fuel injection section. You checked the plugs and they are carbon fouled I presume. The water temp sensor (not the gauge one, the one that tells the ECU the engine is cold) would be 1st. Its all well covered in the FSM where to start and how to check with simple tools like a VOM.

Ill see if I can dig that up
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http://www.atlanticz.ca/zclub/techti...ectionbook.pdf


not a zx but mostly applies for basics.
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post #5 of 14 (permalink) Old 04-17-2017, 09:24 PM
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Garage
FSM for ZX

Here is a link for the ZX

http://www.xenonzcar.com/s130/fsm.php

'79 280ZX Daily
83 slicktop being built
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post #6 of 14 (permalink) Old 04-18-2017, 03:26 PM
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Before you throwing lots of money at expensive parts you probably don't need (what many newbies do) - do these two things:
1. Make SURE your vacuum system is tight. The easiest way to do this is replace all vacuum hoses with new ones. On the ZXs, there are two small lines that go through the firewall and are supposed to run flapper doors for the heater/AC. Those are hard to replace so for the moment, just cap them off.
2. Disconnect, clean (if possible) and reconnect EVERY electrical fitting under the hood and at the ECU. This includes injector plugs, battery terminals, fuses, fusible links, and especially ground wires. If you can get at the plugs to clean them, just plug-unplug numerous times to clean up the connections.
3. (I know I only said two things, but...) Make absolutely sure your battery is tip-top, preferably almost new.
4. Use only NGK or Nippondenso spark plugs. Don't ask me why, but nothing else works half as well.

These cars are very sensitive to good vacuum and good electrical connections. I'm guessing that ust doing these few things will make the car run much better. If it's still kinda funky, they start looking at things like gummy injectors or other fuel probs. With gas blends these days, a car that has sat for awhile, especially outside, can start to get varnishy gas. That might require flushing lines, new fuel filter and possibly getting injectors ultrasonically cleaned.
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post #7 of 14 (permalink) Old 04-19-2017, 10:40 AM Thread Starter
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Originally Posted by Dave M View Post
FSM fuel injection section. You checked the plugs and they are carbon fouled I presume. The water temp sensor (not the gauge one, the one that tells the ECU the engine is cold) would be 1st. Its all well covered in the FSM where to start and how to check with simple tools like a VOM.
The sensor you are talking about is the single wire one at the bottom-most point? In other words, from this sensor, at about 2 o'clock you have the thermotime switch and at about 10 o'clock you have the gauge sensor?
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post #8 of 14 (permalink) Old 04-19-2017, 10:41 AM Thread Starter
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Originally Posted by 6shutr View Post
Before you throwing lots of money at expensive parts you probably don't need (what many newbies do) - do these two things:
1. Make SURE your vacuum system is tight. The easiest way to do this is replace all vacuum hoses with new ones. On the ZXs, there are two small lines that go through the firewall and are supposed to run flapper doors for the heater/AC. Those are hard to replace so for the moment, just cap them off.
2. Disconnect, clean (if possible) and reconnect EVERY electrical fitting under the hood and at the ECU. This includes injector plugs, battery terminals, fuses, fusible links, and especially ground wires. If you can get at the plugs to clean them, just plug-unplug numerous times to clean up the connections.
3. (I know I only said two things, but...) Make absolutely sure your battery is tip-top, preferably almost new.
4. Use only NGK or Nippondenso spark plugs. Don't ask me why, but nothing else works half as well.

These cars are very sensitive to good vacuum and good electrical connections. I'm guessing that ust doing these few things will make the car run much better. If it's still kinda funky, they start looking at things like gummy injectors or other fuel probs. With gas blends these days, a car that has sat for awhile, especially outside, can start to get varnishy gas. That might require flushing lines, new fuel filter and possibly getting injectors ultrasonically cleaned.
Good info here, thank you
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post #9 of 14 (permalink) Old 04-19-2017, 11:51 AM
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Originally Posted by dcooper23 View Post
The sensor you are talking about is the single wire one at the bottom-most point? In other words, from this sensor, at about 2 o'clock you have the thermotime switch and at about 10 o'clock you have the gauge sensor?
the single wire is the temp gauge sensor, there should be a two conductor small sensor, that is the temp sensor for the ECU. the larger two conductor is a thermos time switch used to activate the cold start valve.


You really just need to read read read the ECU section and do the testing there. As mentioned before don't start throwing money at it with out 1st clean and check all connections and grounds. Then go thru the diagnostics per the FSM.
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post #10 of 14 (permalink) Old 04-19-2017, 02:27 PM Thread Starter
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the single wire is the temp gauge sensor, there should be a two conductor small sensor, that is the temp sensor for the ECU. the larger two conductor is a thermos time switch used to activate the cold start valve.


You really just need to read read read the ECU section and do the testing there. As mentioned before don't start throwing money at it with out 1st clean and check all connections and grounds. Then go thru the diagnostics per the FSM.
I understand that but about this sensor: I do not have another two conductor sensor aside from the thermotime switch. In reading the FSM, it says that only Canadian models get the type that you are talking about. I know my car is an American issue and I do not have it
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