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Discussion Starter · #1 ·
I haven't been here for months, wild new format!
Now my problem:
A couple days ago my 79 zx started to intermittently miss on #4, no big deal, sticky injector, so today I replaced the injector and now it's running awful!
Way rich across the board as far as I can tell.
I checked all the connections,the throttle position switch,the cold start valve,the AFM moves smoothly and it's running so rich(white gassy smoke) that I can't tell if the fuel pressre regulator is ok or not.
I tested the diaphram and it's not ruptured, holds a vacuum, and in the past when I disconnected the regulator all that happened is the idle speed picked up, no rich problem like I have now.
So I don't know where to look next. I can hear the injectors working.....
And when I pulled the cold start valve out of the manifold, I just left the holes open and started it up, ran at a higher speed but all the extra air made it run about normal.
What should I look at next?
Any help greatly appreciated.
Now I'm going to the archives and will check back for suggestions,gotta get this car running right so I can get to work tomorrow.
Jeff 79zx ;^(
 

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Check the Head Temperature Sensor. I think on your year it is called a water temperature sensor. If there is a sensor below the #5 spark plug then it is a head temperature sensor. If it is bad it will tell the computer that it is cold and make the engine run rich.

Hope this helps you out
 

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Discussion Starter · #3 ·
Check out the O2 sensor, if you had a bad injector it is possible that it screwed up the sensor. The water temp sensor is another good possibility.
Good Luck,

Russel 83ZXT
 

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Discussion Starter · #4 ·
RE: HELP! 79zx runs rich no head temp sensor.

Thanks for the suggestion Russ, this 79 I've got is a fed. non cat. car, no head temp sensor.
What else could tell the injectors to give too long of pulse or cause the car to run so rich?
I'm getting near the panic stage, this is my commutor car and has always ran ok until I put this injector in.
Could this injector have the wrong resistance in the windings and be loading the whole injector circuit down?
Jeff 79zx
 

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Discussion Starter · #5 ·
Thanks for the suggestion russell but this 79zx doesn't run an o2 sensor, I'll check the water temp sensor next.
This definately shoots my one day off to **** damnit!
Keep the suggestons comin in folks!
Thanks jeff 79zx
 

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Discussion Starter · #6 ·
Try checking the "thermotime" switch (or sensor).
This is what controls your cold start valve, and may be telling ti to continuously pump in more gas.
 

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Discussion Starter · #7 ·
RE:Thanks Guys!

Well we got it cured!
It was indeed the water temp sensor.
By some freak of nature it decided to go open(infinite resistance) at the exact same time I got around to changing the injector.
Man I thought something terrible and mysterious was going on,I've changed injectors before and never had any problems.
Bummer is it's now going on 6 p.m.,took me four hours to track down another sensor, and I did more today than I normally do at work.
Some day off eh?
Thanks,
Jeff 79zx
 
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