# 95 Altima IAC/AAC



## rjab (Jan 29, 2006)

I've been chasing an intermittent starting problem for 2 weeks, so now joined this forum for help.

With the engine key on, the Idle Air Control /Auxiliary Air Control valve keeps turning on and off, that is the solenoid engages, then disengages a few secs later. With the distributor out, but hooked up, I was rotating the full 360 degrees, to ensure the power transistor for the coil supplies the needed ground, and noticed this. If I disconnect the electrical connector to the distributor, it stops. I don't believe I noticed this before. The solenoid is loud enough, to barely hear it from inside the car. Does not matter where the distributor shaft position is. Is this normal for it to cycle on and off with the key on but not running?

Also, I have a 12v test light on the negative coil wire. When the power transistor is off, there is 12 volts there, so light is on. When the ECM provides voltage to the base of the transistor, it turns on, the collector to emitter is shorted to ground, providing a ground path to charge the coil. Take away the base voltage, transistor is open, secondary field of coil collapses with spark.
Question is, the light I have on the coil goes dim for a couple of degrees of distributor rotation, just before it goes out completely when the transistor is on. I find this weird, as it means the transistor is leaking a bit. I would think the thing would quickly turn on/off. Is the dim light enugh reason to try a new one?
I'd try a new one, but they are $90. Already spent 180 on a distributor, which I needed anyhow, as I found it full of oil when I started this. Spent $97 on a new coil, since mine had a secondary impedance of 15M when hot, where spec is 11.5-12.5. Fortunately, I was able to return the coil. 

Thought this was fuel at first, since I had spark when it would not start. Fuel pressure measures correctly, and regulator tests correctly. Changed filter for grins.

When it failed, it was once every 3 days or so. By the time I would tow my wife home, it usually started after shoving it in the garage. Became more frequent, and found I had no spark. At first, plugs were clean, now very rich.


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## gfriedman (Oct 12, 2005)

Hmmm alot of info there. First off, the IAC cycles with input from the ECM. That's normal so I don't think thats causing your starting issue. From it being intermittant and plugs showing rich I would say there is a problem with your MAF. First off I would check the ECU for any stored codes. Next I would clean and check all the MAF connectors wires for continuity. Then I would test the MAF to see if it went south.


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## jserrano (Oct 27, 2004)

That electrical plug next to the distributor is where the ECU gets it's timing signals to control the power transistor and fuel injectors. 

When the intermittent NO START comes back, ascertain that you definitely don't have SPARK. If so, you can try this,

- Remove the distributor and leave the plug connected. 
- Next, put the ignition key to ON position (NOT START).
- Rotate the distributor shaft by hand.
- Listen for 'clicking' sound from the fuel injectors.
- ...also the ignition coil high voltage wire should arc when close to ground.

If there is no spark from the ignition coil then troubleshoot the primary low voltage ignition system. Otherwise, you are looking at the secondary high voltage problem.


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## rjab (Jan 29, 2006)

I did do that. It acts as it should when rotating the distrbutor by hand, out of the engine. All 4 plugs spark good. Then when installed in the engine, and cranking the engine, the spark is intermittent.

I replaced the $90 power transistor, but that didn't help. One thing that troubles me is the fuel pump relay keeps turning on, then off every 3-5 secs. Manual says it should turn on for 3 secs, then if there is no electrical pulses coming from the distributor, it should shut off. The output from the optical pulser in the distributor is 5vdc. Each time this cycling takes place, it momentarily drops to .2vdc. Seems like the distibutor may be at fault, but it is new (rebuilt).

I'll check the timing again, but I'm about to give up and take it in to a Shop. I hope this strange behavior isn't the ECM.

Keep the suggestions coming though. Wednesday is when I take it in. 2 nights to find the problem.


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## gfriedman (Oct 12, 2005)

Dude, I can't tell you how many times rebuilt parts turn out to be shit. The rebuilders often just clean 'em and throw 'em in a box to be resold. If there is still a warranty on it then get it replaced.


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## jserrano (Oct 27, 2004)

Check to see if the 12V or ground (orange and black wire) drops out when the optical voltage drops. Ground comes from intake manifold ground and power from the ECM relay. The fuel pump relay is also tied to the ECM relay, I believe.


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## rjab (Jan 29, 2006)

I think I may have found the problem. The connector to the distrbutor is making intermittent connection. I had the distributor off, and had spark when spinning the rotor shaft slow, but none when spinning fast. The connector retaining clip was broken off when I got the car, but I ignored it. Pressing it in firm helped, but pushing on the wires did the trick. The connector pins/clips look OK under magnification, but perhaps there's a problem inside. 
Can't get a connector from Nissan, so I'll search the junk yards. Hard to believe it would be that simple after all this, but I'll find out after I get a new connector.


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## jserrano (Oct 27, 2004)

Nice to hear that! For the meantime, you could probably just squeeze the female pins some so that is locks tighter on the male pins. (Don't get excited guys.)


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## rjab (Jan 29, 2006)

Guy’s,

This problem was finally resolved yesterday. To the guy who said “Dude, get another distributor,” you were right. Based on my 3 weeks of messing with this, the problem was as follows:

1.	Original Distributor was leaking oil internally, which you all know is common. Optical sensor and disk were coated with oil, causing intermittent spark. 
2.	Secondary problem was with the connector that plugs into the distributor. Mine was missing the retaining tab, so did not lock in correctly. It was broke when I bought the car. I believe I made it worse installing it and removing it so many times.
3.	The rebuilt distributor was faulty. 

The fact that the fuel pump relay kept cycling with the key on should have been a clue. It bothered me, since the manual stated that the ECM turns it on one time, and if it receives no electrical pulses from the distributor, it will turn off the fuel pump relay. You should get 5vdc out of the blue wire from the distributor, mine kept transitioning from 5vdc to .120 vdc. I couldn’t accept the fact that the new distributor was at fault.

Something else that I found weird, was every junk yard I went to was missing the connector. One guy who had one wanted $50, saying they were a high demand item. I finally found one for $20. I know mine was making poor contact, but I think this was a secondary issue.
When I returned the distributor, the parts guy was comparing it with the one he was giving me, and noticed debris between the disk and the optical sensor. I wish I would have done the same thing, as it was probably my problem, but we both decided going with the newer distributor was my best bet.

Hope this information will help someone else.


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