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Discussion Starter #1
Been having trouble with my 85 300ZXT lately missing and cutting out. Checked the MAF sensor, changed the fuel filter and the fuel pressure regulator (based upon some of the codes i was getting).

This still has not solved the problem; runs fine for about ten minutes then starts missing (or stuttering) and smells like its running rich. If you try to give it throttle, it bogs down and sometimes backfires unless I down gear to get the rpm's up first. Has a low idle as part of this problem.

The other strange part is that there is an electric motor on the passenger side front just up behind the air dam that is now running all the time. I used to just hear it before the car started. Now it runs non-stop and its blowing air through the small black tubing attached to it.

does any one know what this motor is and what it controls or about what might be causing the stalling/missing problem?
 

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that motor you hear is an injector cooler fan. it normally runs after the car is shut off to prevent the injectors from overheating. it isnt the cause of the problem.

if you have a haynes maual trouble shoot it. check things that are heat sensetive.

hope it helps
zelotic
 

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THe motor you hear sounds like the air supply to cool the injection system
(supposed to protect from vapor lock). The reason it runs all the time is your temp sensor is stuck open (bad). disconnect the power to the motor, or fix the sensor.

intermittant starting or short term running might be: MAP going bad, or
fuel pump/fuel pressure regulator not developing and holding pressure,
or O2 sensor bad.

Try disconnecting your neg terminal on battery for a few minutes, reconnect and try starting again. Check your ECU codes first before disconnecting the battery.
 

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The electric motor thing is probably a vacuum pump that helps the vac tank keep enough vac to operate interior HVAC and cruise control when on boost.
The vac tank has a switch that turns the vac pump on when the vacuum in the tank gets to a low level. The vac tank is connected to the plenum so it gets vac from there if available.
If the vac pump runs all the time then then either the switch is bad or there is a vac leak.

If there is a vac leak then that may be causing or contributing to the missing and cutting out you describe.

After replacing the parts you described, did all error codes go away?
 

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the temp sensor for the injector cooling fan is located on the drivers side of the lower intake plenum....... its pretty hard to get to, and youll have to pull the upper intake off to do this....oh and its $50 at the dealer. If ou live in a cool climate then I wouldnt really worry about the cooling fan too much. but if your in the south then get it done, or you might find yourself vaporlocked on the side of the highway this summer.
 

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Don't listen to anyone but Mister_T, They are all way off.

It is not your injector cooling fan, that is on the drivers side of the engine bay, right next to the headlight.

Your problem is most likely a vacuum leak. The reason the vacuum pump is running all the time, is becuase it can't keep up with the leaking hoses. Search around your engine bay for a hose that might've gotten blown off, or a leak around your MAF. If your still having problems finding it. You can look on twinturbo.net for a boost leak detector. It's basically a 3" piece of piping with a hookup that fits to a bike pump. You pump it up, and listen to where air is escaping.
 

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Discussion Starter #7
Thanks guys for the input. I knew it wasn't the injector cooling fan cause I know where it is and how it sounds.

I''ll go with the idea that it is the vacuum pump that is running and try to figure out where the leak is.
 

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take a look at the hose connecting to the valve next to the battery. on my 86T that had split, causing the vacuum pump to stay on all the time. very hard to spot.
 

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on my 86 na the injector cooler fan is on the passenger side.
 

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tn85man: "just up behind the air dam"

On turbos, the injector cooling fan is on the other side, right by your Coil.

Just rip that **** out. You don't need it, and it'll create less noise.
 

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I have the same problem in my car. Turns out there were a couple of vac hoses around the throttle body that were falling apart. When I tried removing them, they just fel apart in my hands. That's a good place to check since there are a lot of vac hoses under the throttle body.

zelotic: if that is the injector cooling fan you pointed out, what is the thing behind the driver side headlight?

Where in TN are you tn85zman?
 

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valkyrievf2x wrote:
"zelotic: if that is the injector cooling fan you pointed out, what is the thing behind the driver side headlight?"

You would find that it is an AIV unit.
 

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Thought I'd ask. never seen it before in either of my Z's (85Na and 85T). I think AIV is "auxiliary Intake Valve" or something like that.

Learned something new today:)
 

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i hadnt a clue what it was until yall said it was the AIV
 
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