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Discussion Starter · #1 ·
Good morning friends,
Just purchased a dream car that I have always wanted that has been sitting for 10 plus years and now I picked it up with the hoping of getting it running again.
I have put in new Injectors, Fuel pump, had the Head resurfaced with new seals. To start it you have to hold a little throttle for a minute or two then it will idle fine for another min or 2 the you have to hold a little throttle again for another minute other wise it idles so slow it dies most on the time but now at this point it has now gotten through the warming up stage running just fine....
I have had some people say that my Idle air control valve is bad(vacuum type with water line under it also with electrical plug not fuel injected type)is bad but others have said my ECU is bad.
Have any of you had this problem and also I am a good parts changer but not a great engine mechanic so if you might know of a shop in Sacramento CA that still works on these great cars I would so appreciate it.
Brian
 

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I had a very similar issue. My fix involved 3 different tasks:

1) Leaking fuel injector. I replaced all 6 (since it needed new ones anyway). The worst offender had a busted lower seal that created a pretty massive vacuum leak.
2) Replacing vacuum hoses. Several vacuum hoses were cracked from age, replacing them fixed these additional vacuum leaks.
3) Replacing the AAR (What you refer to as the Idle Air Control valve). Mine was stuck closed, and therefore was not allowing enough air at idle to sustain the engine after a cold startup. Just like yours, mine would idle just fine after the engine was up to operating temp.

Take a look at your AAR (slide off both hoses, disconnect the electrical connector, and undo both 10mm bolts holding it down) and you may find that it is also stuck closed. There are several threads on this site and others detailing proper operation of the part. The most important part for you, though, is to ensure it's open enough to allow for extra air to bypass the throttle at cold engine temps.

Vacuum leaks are also well documented. Use your ears as well as your eyes. Good luck!
 

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To clarify, I wouldn't replace your AAR until you've verified that it is not operating properly and cannot be fixed. It's a very mechanically simple device. Sometimes it's possible to coax a poorly operating instance back to life.
 

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Discussion Starter · #4 ·
Thank you very much, Yes that was a main thought at the beginning but the biggest problem is that part is not available any more.... I have search and searched for it a long time....
Mine looks like this.....
Machine tool Machine Metal
 

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Discussion Starter · #5 ·
I will test it several times to check it... I have replaced pretty much every vacuum hose then spraying choke cleaner all around all vacuum areas to see if any idle change, wasn't any....
 

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Another easy way to test the AAR circuit is to "bypass" the part entirely and use a length of hose in its place. That way, you can simulate the cold operation of the AAR (obviously the hose is not going to close when your engine gets up to operating temp, so I made sure and only used that as a test).

I'm a fan of isolating problems as much as possible so as not to introduce unknown variables. The "AAR bypass" allowed me to do that while I fixed a couple more vacuum leaks and I was able to see definite improvements in cold engine operation. Fixing the vacuum leaks solved my problem where I had to crank the starter for 10 or 15 seconds before the engine would reliably turn over. Fixing the AAR solved the "too low RPM @ cold engine idle" that meant my engine would choke and die. Now that both of those issue are fixed, it runs like a dream!
 

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Discussion Starter · #7 ·
Thank you very much, I'll give that a shot... Question?, What does that electrical wire that plugs into the AAR run back to? Does it run strait back to the ECM or to the Temp control sender? Was wondering how to also check that wire harness that plugs into the AAR
 

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Hopefully when you got new injectors you got them for a turbo. You don't want to put non turbo injectors in a turbo car. Can cause some serious problems down the road. Also, there is a difference between the AAR and the IACV and they're frequently identified wrong. Your car has both units on it. The pic you showed is the AAR. The AAR can usually be fixed. I sell rebuilt ones even for the turbo cars. They're not cheap though so be advised you'd have to save up to get one of them. When your car gets warmed up, what is the idle rpm at? I'd bet money that it's too low. It should be at 900 rpm in neutral or even 925 especially with an automatic trans. I'd hazard a guess to say that it's probably about 700 or 750 which is typical. The only way to raise the idle speed is to adjust the throttle plate set screw up which has a lock nut on it and the screw is upside down. If you can't get the screw adjusted you may have to pull the throttle body off and do it that way. Turn the screw half a turn to 1 full turn and see what that does. The may solve your problem at least temporarily. Z man of Washington
www.zspecialties.com
www.datsunstore.com
360-668-2979
 

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Discussion Starter · #9 ·
Hopefully when you got new injectors you got them for a turbo. You don't want to put non turbo injectors in a turbo car. Can cause some serious problems down the road. Also, there is a difference between the AAR and the IACV and they're frequently identified wrong. Your car has both units on it. The pic you showed is the AAR. The AAR can usually be fixed. I sell rebuilt ones even for the turbo cars. They're not cheap though so be advised you'd have to save up to get one of them. When your car gets warmed up, what is the idle rpm at? I'd bet money that it's too low. It should be at 900 rpm in neutral or even 925 especially with an automatic trans. I'd hazard a guess to say that it's probably about 700 or 750 which is typical. The only way to raise the idle speed is to adjust the throttle plate set screw up which has a lock nut on it and the screw is upside down. If you can't get the screw adjusted you may have to pull the throttle body off and do it that way. Turn the screw half a turn to 1 full turn and see what that does. The may solve your problem at least temporarily. Z man of Washington
www.zspecialties.com
www.datsunstore.com
360-668-2979

Ok yes your pretty much there..... I have adjusted the idle screw up which is under the manual ball joint linkage to open the throttle a tad to about 1100 rpm while in park then when you put it in Drive it drops to about 850 rpm, but should it have some kind of censer that automatically adjusts the rpm when going from park/neutral to drive/reverse?
as far as the injectors, I will have to look that up and dee what injectors I put in....
Thank you for your response, I really like my car and want to get it on the road..
Brian
What kid of cost am I looking at for the AAR rebuilt if you don't mind me asking... I have not been able to find one, all I find is that they are discontinued....
 

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Another input, twice a year depending on where you live, I clean my ECU's with avionics cleaner/electronics. then use the air can stuff to blow it out. I f you live in high humidity areas. works for me all the time.
 

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Discussion Starter · #12 ·
Another input, twice a year depending on where you live, I clean my ECU's with avionics cleaner/electronics. then use the air can stuff to blow it out. I f you live in high humidity areas. works for me all the time.


Well thank you , I will definitely give that a try....
 

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Discussion Starter · #13 ·
I'm finding out there is another problem of once its idling at around 900 rpm then I put it in Drive the idle comes down to about 400 and dies...... if I adjust the idle while id Drive (parking brake on) to 900 rpm then put it bake in park or neutral then the rpm jumps up to around 1200......
Now I know there is a switch or sensor that is supposed to automatically adjust this but I have not been able to figure out where it is or how to test it?
Have any of you had this experience?
Brian
 
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