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Discussion Starter #1
Here is my problem. When I first start my Z, when it is cold, it runs like a champ. After it gets warm, right when the needle on the temp gauge moves, it starts to miss and run very bad. The idle will fluctuate +/- a few 100 rpms, the throttle will lerch when i reach 2000 rpm and then take off like a bat out of ****. This is real bad in stop and go traffic.

I have replaced cap and rotor, plug wires, plugs(ngk R), water temp sensor, fuel injectors, battery cables, cleaned of ALL the connectors on EVERY elctrical plug, set the throttle position sensor, timed the car, and tested the mass airflow sensor. It still does this.

My question is this what does the thermotime sensor do? Could it be the fuel pressure regulator? I did notice one thing that baffles me. The air regulator (i think thats what it is. It has an electrical plug on it with two hoses and it is kinda round on top of the intake manifold.) the electrical piece inside the tube keeps coming out. It does not unplug itself but rather the whole assembly comes out.??

Any help anyone can give me would be appreciated.
Sorry so long.
Tim 78 280z
 

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> Here is my problem. When I first start my Z,
> when it is cold, it runs like a champ. After
> it gets warm, right when the needle on the
> temp gauge moves, it starts to miss and run
> very bad. The idle will fluctuate +/- a few
> 100 rpms, the throttle will lerch when i
> reach 2000 rpm and then take off like a bat
> out of ****. This is real bad in stop and go
> traffic.

> I have replaced cap and rotor, plug wires,
> plugs(ngk R), water temp sensor, fuel
> injectors, battery cables, cleaned of ALL
> the connectors on EVERY elctrical plug, set
> the throttle position sensor, timed the car,

> and tested the mass airflow sensor. It still
> does this.

> My question is this what does the thermotime
> sensor do? Could it be the fuel pressure
> regulator? I did notice one thing that
> baffles me. The air regulator (i think thats
> what it is. It has an electrical plug on it
> with two hoses and it is kinda round on top
> of the intake manifold.) the electrical
> piece inside the tube keeps coming out. It
> does not unplug itself but rather the whole
> assembly comes out.??

> Any help anyone can give me would be
> appreciated.
> Sorry so long.
> Tim 78 280z

I am not familiar with the 280, but does it have a coolant temp sensor? I know mitsubishis run poorly on bad sensors.

Hope this helps, Evan
 

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> Here is my problem. When I first start my Z,
> when it is cold, it runs like a champ. After
> it gets warm, right when the needle on the
> temp gauge moves, it starts to miss and run
> very bad. The idle will fluctuate +/- a few
> 100 rpms, the throttle will lerch when i
> reach 2000 rpm and then take off like a bat
> out of ****. This is real bad in stop and go
> traffic.

> I have replaced cap and rotor, plug wires,
> plugs(ngk R), water temp sensor, fuel
> injectors, battery cables, cleaned of ALL
> the connectors on EVERY elctrical plug, set
> the throttle position sensor, timed the car,
> and tested the mass airflow sensor. It still
> does this.

> My question is this what does the thermotime
> sensor do? Could it be the fuel pressure
> regulator? I did notice one thing that
> baffles me. The air regulator (i think thats
> what it is. It has an electrical plug on it
> with two hoses and it is kinda round on top
> of the intake manifold.) the electrical
> piece inside the tube keeps coming out. It
> does not unplug itself but rather the whole
> assembly comes out.??

> Any help anyone can give me would be
> appreciated.
> Sorry so long.
> Tim 78 280z

With the problems that you've decribed, it's a good idea to check the fuel system. Start back to front, and check evrything. (Filter, hoses etc.) If you have sensors, and wires that are falling out, that can't be helpinng, so it would be a good idea to get that fixed, of course, so that you don't have more than one thing causeing the car to malfunction.

Check the air intake. Make sure that there is nothing that could be restricting air flow. Make sure that nothing got through the filter, and is now clogged between the filter and the manifold.

Good luck, and let us know how it turns out.

Chris Behney
Redline Autosports
 

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your air regulator is bad. there is a disc inside the unit when it is cold it lets there air to bybass the throttle plate. when the engine warms up the disc closes. the electrical connector is connected to a bimetallic spring that when heated will close the disc. the problem with your air regulator is it is creating a vacumn leak when warm and when you get to 2000rpm your vacumn is around 0.

hope this helps you out.

> Here is my problem. When I first start my Z,
> when it is cold, it runs like a champ. After
> it gets warm, right when the needle on the
> temp gauge moves, it starts to miss and run
> very bad. The idle will fluctuate +/- a few
> 100 rpms, the throttle will lerch when i
> reach 2000 rpm and then take off like a bat
> out of ****. This is real bad in stop and go
> traffic.

> I have replaced cap and rotor, plug wires,
> plugs(ngk R), water temp sensor, fuel
> injectors, battery cables, cleaned of ALL
> the connectors on EVERY elctrical plug, set
> the throttle position sensor, timed the car,
> and tested the mass airflow sensor. It still
> does this.

> My question is this what does the thermotime
> sensor do? Could it be the fuel pressure
> regulator? I did notice one thing that
> baffles me. The air regulator (i think thats
> what it is. It has an electrical plug on it
> with two hoses and it is kinda round on top
> of the intake manifold.) the electrical
> piece inside the tube keeps coming out. It
> does not unplug itself but rather the whole
> assembly comes out.??

> Any help anyone can give me would be
> appreciated.
> Sorry so long.
> Tim 78 280z
 

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Discussion Starter #5
The thermotime switch opens the fuel nozzle in the throttle body during cold start. After warming up it shuts off the fuel to the nozzle.

I suspect a bad air flow meter. Just went through this whole bunch of crap myself. To test this theory you need to put a resistor (400 ohm up to 1k ohm) inline with the temperature sensor black wire. This connector is located just after the AFM and the throttle body and strapped to the metal lines. Looking at the engine from the front of the car the temp sensor is the one on the right or drivers side on the thermostat housing. There are 3 things there. Water temp sensor for guage, thermotime switch and the temperature sensor to the computer. Solder a male and female pigtail connectors to the resistor and plug in with the black wire. Also fix whatever is loose that you mentioned.. Let me know what happens..

Joe
 

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Discussion Starter #6
> The thermotime switch opens the fuel nozzle
> in the throttle body during cold start.
> After warming up it shuts off the fuel to
> the nozzle.

> I suspect a bad air flow meter. Just went
> through this whole bunch of crap myself. To
> test this theory you need to put a resistor
> (400 ohm up to 1k ohm) inline with the
> temperature sensor black wire. This
> connector is located just after the AFM and
> the throttle body and strapped to the metal
> lines. Looking at the engine from the front
> of the car the temp sensor is the one on the
> right or drivers side on the thermostat
> housing. There are 3 things there. Water
> temp sensor for guage, thermotime switch and
> the temperature sensor to the computer.
> Solder a male and female pigtail connectors
> to the resistor and plug in with the black
> wire. Also fix whatever is loose that you
> mentioned.. Let me know what happens..

> Joe

Fix the Air Regulator first had the same problem the guts kept falling out. I just pulled one from a junkyark Z or ZX non-turbo. Just make sure it looks the same. Works great now. Good luck. Sam 75 280z
 

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To add to Grandpa Joe:
The single wire sensor just provides feedback to your water temperature gauge inside. The Thermotime switch(the larger of the two - two wire sensors) fires your cold start injector (the 7th injector that is mounted on your intake manifold) for start-up when the engine is cold. The engine temperature sensor feeds back to the ECU which controls the pulse duration of your other six injectors. If it is shorted or dead it will literally choke your engine to death.
The air regulator allows additional air to the engine during warm-up. If it doesn't open your engine will idle like crap until it warms up and then it will be fine. If it is stuck open your engine will idle fine cold and then give you fits.
I just ordered one from Nissan - $102. Get the hoses on either side of it and also replace the reinforced hoses that route the radiator water through its base to heat it up too. They are probably all on their last legs. Mine are.
Have fun.
Phantom

> The thermotime switch opens the fuel nozzle
> in the throttle body during cold start.
> After warming up it shuts off the fuel to
> the nozzle.

> I suspect a bad air flow meter. Just went
> through this whole bunch of crap myself. To
> test this theory you need to put a resistor
> (400 ohm up to 1k ohm) inline with the
> temperature sensor black wire. This
> connector is located just after the AFM and
> the throttle body and strapped to the metal
> lines. Looking at the engine from the front
> of the car the temp sensor is the one on the
> right or drivers side on the thermostat
> housing. There are 3 things there. Water
> temp sensor for guage, thermotime switch and
> the temperature sensor to the computer.
> Solder a male and female pigtail connectors
> to the resistor and plug in with the black
> wire. Also fix whatever is loose that you
> mentioned.. Let me know what happens..

> Joe
 

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107,695 Posts
Discussion Starter #8
Re: attn: Grandpa Joe, My problematic Z (long)

> The thermotime switch opens the fuel nozzle
> in the throttle body during cold start.
> After warming up it shuts off the fuel to
> the nozzle.

> I suspect a bad air flow meter. Just went
> through this whole bunch of crap myself. To
> test this theory you need to put a resistor
> (400 ohm up to 1k ohm) inline with the
> temperature sensor black wire. This
> connector is located just after the AFM and
> the throttle body and strapped to the metal
> lines. Looking at the engine from the front
> of the car the temp sensor is the one on the
> right or drivers side on the thermostat
> housing. There are 3 things there. Water
> temp sensor for guage, thermotime switch and
> the temperature sensor to the computer.
> Solder a male and female pigtail connectors
> to the resistor and plug in with the black
> wire. Also fix whatever is loose that you
> mentioned.. Let me know what happens..

> Joe

Joe,

I have problems similar to which have been described. I used a 1k resistor in line and the car ran great, under 2000 rpm I use to have a lag the resistor cured that bigtime. I ran great much longer than usual, it did start to cut out again though not as bad. Does this mean I need an air flow meter replacement?

Clif
 
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