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My 76 Z has had this reoccuring problemb for about 2 years. One minute ,It can be running fine and suddenly have rich mixture. While in rich mixture ,under load the engine will die at about 2500rpm. If turned off while under rich fuel mixture, the car will not restart. Waiting 20min to an hour after it happens will {usaly}usaly find it running fine again. My friends, I'm tired of getting 10mpg and being stranded on the side of the road. Please, help me.
I've tried many things to fix it. It has a new battery and alternator, new plugs and rotor.new cap and coil wire. Tried new coil. Reluctor and contacts are a bit dusty but no sign of burning. It has a 1 year old Air Flow Meter (rebuilt Motorsport) and a new fuel filter and clean air filter. I used to have two Z's and tried swapping out Air Regulator and Computer. Two of my injectors look like they've been replaced . I've had then out to clean them (and used a fuel additive) and noticed #6 had most of its ceramic broken away from the nozzle. I have cleaned the Throttle Body and ensured a clean Vacuum Advance line.
When it's having a bout of gout (rich mixture) and I'm on the side of the road, under the hood of a barely running loved one, pulling the lead from the Cold Start Valve dosen't help. Bypassing the Thermotime and Water Temperature Sensor dont help either. Pulling the Vacuum Line dosen't help. Leaving it and walking away dosen't help.
I have a Water Temperature Sensor on order, should be here in four days. If that dont do the trick, what should I try next ?
I know I'm new to this forum but I realy need some advice from people who love their Z's like I love mine, and not from someone who sees me as a customer. ($800 for new injectors [ : ( ] give me a break ) Any help from Z doctors out there would be greatly appreciated by me (and my feet). This ones got me stumped.
 

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Squalor:
Let's get into basics here. If you are pouring huge clouds of black smoke out the back you are running rich. For you to be running rich your ECU has to think the engine is cold. I recently went through this and it turned out that the bullet connectors where the lead from the engine temperature sensor connects into the wiring harness ( the lump in the wiring about 12 - 16 from the sensor) were corroded and reading massive (infinite) resistance so the ECU thought the engine was cold. It put the fuel injectors into a long duration pulse mode and literally choked the engine to death. It also gas fouled the plugs so I had to pull them, thoroughly clean and dry them, and then re-install them. If you don't have a '76 Z Nissan Service Manual - get one. Call Nissan Service Publications at (440) 572-7280. It costs $73 and will save you many times over that. The new air regulator and engine temperature sensor must have set you back at lest $200 already.
Since you say your problem is intermittent I'd be looking for those bullet connectors NOW. That is how mine started out - intermittent - and then it became permanent and my car ws down for a week before a friend of mine told me where to look.
The manual will tell you how to test the engine temperature sensor and the thermotime switch to ensure they are OK. Do that before you install the new engine temperature sensor and maybe you can get a refund on it and pay for the manual!!??
Good Luck - E-mail me directly if you have any more questions.
Phantom

> My 76 Z has had this reoccuring problemb for
> about 2 years. One minute ,It can be running
> fine and suddenly have rich mixture. While
> in rich mixture ,under load the engine will
> die at about 2500rpm. If turned off while
> under rich fuel mixture, the car will not
> restart. Waiting 20min to an hour after it
> happens will {usaly}usaly find it running
> fine again. My friends, I'm tired of getting
> 10mpg and being stranded on the side of the
> road. Please, help me.
> I've tried many things to fix it. It has a
> new battery and alternator, new plugs and
> rotor.new cap and coil wire. Tried new coil.
> Reluctor and contacts are a bit dusty but no
> sign of burning. It has a 1 year old Air
> Flow Meter (rebuilt Motorsport) and a new
> fuel filter and clean air filter. I used to
> have two Z's and tried swapping out Air
> Regulator and Computer. Two of my injectors
> look like they've been replaced . I've had
> then out to clean them (and used a fuel
> additive) and noticed #6 had most of its
> ceramic broken away from the nozzle. I have
> cleaned the Throttle Body and ensured a
> clean Vacuum Advance line.
> When it's having a bout of gout (rich
> mixture) and I'm on the side of the road,
> under the hood of a barely running loved
> one, pulling the lead from the Cold Start
> Valve dosen't help. Bypassing the Thermotime
> and Water Temperature Sensor dont help
> either. Pulling the Vacuum Line dosen't
> help. Leaving it and walking away dosen't
> help.
> I have a Water Temperature Sensor on order,
> should be here in four days. If that dont do
> the trick, what should I try next ?
> I know I'm new to this forum but I realy
> need some advice from people who love their
> Z's like I love mine, and not from someone
> who sees me as a customer. ($800 for new
> injectors [ : ( ] give me a break ) Any help
> from Z doctors out there would be greatly
> appreciated by me (and my feet). This ones
> got me stumped.
 

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I have a '73 240Z that had the same problems too. I changed my battery, alternator, mech. fuel pump, fuel filter, air filter, contact points, distributor, spark plugs and wires. It ended up being my elec. fuel pump. It all started when I was going arould 130mph. I heard a big boom, and from then on I only went slower. 120, 110,100, and so on until it only went 20mph. It hesitated while going those speeds and it wouldn't go any quicker. The worst was when it ckocked from 50mph and under, it died and I had to pull over for about 10-15 minutes each time it died. Good luck finding the problem.
 
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