# 97 Altima idle speed unstable



## Redcar (Aug 4, 2005)

Hello all, I am new here. 

My 97 altima recently had idle problems. The idle of the car was normal (~750) when I stopped before a red light and AT was at "D". However, if I
applied any load to the engine at this time, for example, turned on A/C, turned the steering wheel, press the PowerWindow button, the idle dropped to 500 and backed to 750 in about 0.5s. At mean time engine vibration got worse. It sounds to me that ECM tried to maintain the idle at 750 and sent the instruction, but there was a hesitation for the idle to stablize at that point. I also noticed that in local run (30~40mph) if I push the brake slowly, the ilde also drops to 500 and backs to 750 in 0.5~1s delay.

The car just passed smog test in CA and the emission output was very good - emission polluents well below average.

I tried to fix the problem by a major tune-up, in which i changed spark plugs, wires, distributor cap, air filter and fuel filter. After the tune-up the car was more powerful, but the idle problem was unresolved.

Any ideas?


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## LONDONDERRY (May 19, 2004)

Look at the idel air control valve, it may be getting clogged. My car has a similar problem as well. 



Redcar said:


> Hello all, I am new here.
> 
> My 97 altima recently had idle problems. The idle of the car was normal (~750) when I stopped before a red light and AT was at "D". However, if I
> applied any load to the engine at this time, for example, turned on A/C, turned the steering wheel, press the PowerWindow button, the idle dropped to 500 and backed to 750 in about 0.5s. At mean time engine vibration got worse. It sounds to me that ECM tried to maintain the idle at 750 and sent the instruction, but there was a hesitation for the idle to stablize at that point. I also noticed that in local run (30~40mph) if I push the brake slowly, the ilde also drops to 500 and backs to 750 in 0.5~1s delay.
> ...


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## Redcar (Aug 4, 2005)

*Thanks for your input*

Did you fix the problem after you cleaned the IAC valve?
I guess the IAC valve is in the throttle body. Is it a huge work to clean it? Where can I find the instruction on how to clean it?

Your reply is appreciated.


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## KA24Tech (Feb 2, 2004)

The IACV is located under intake on the front of the engine,which happens to be the opposite end from the throttle body. First pull the intake tube from the inlet of the throttle body. Then with a flashlight open the throttle plate to inspect the condition inside the TB. My guess it is really dirty and the air bleed is plugged. I think the IACV is working since it comes back up after a second although as Frank says it may be dirty as well.
To clean the throttle body you can hold open the throttle plate and then spray it with carb and choke cleaner. Let it sit for a few seconds and then scrub it with an old toothbrush. Then spray it clean. Hold it open for awhile after you have finished to allow part of the cleaner to evaporate and then start it up. 
Inspect the spark plugs and do a tune up if it has been a while. Also try running a product I recommend all the time from BG called 44K with a tank of premium fuel. This should help it as well.

Troy


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## Redcar (Aug 4, 2005)

*Thanks Troy.*

Just bought a Haynes repair manual. Will clean IACV and TB to see if things will get better.


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## speedman (Feb 4, 2005)

*Hey!*

I have a 97 altima manual 75,000. Same problem and a few other ones. Let me know how it goes. Thanks.


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## jserrano (Oct 27, 2004)

Also check the EGR valve for carbon buildup.


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## duke3478 (Aug 11, 2005)

listen to your ALTERNATOR, too. Since you notice your problem is triggered by amp draw, the alternator could be on the way out.

You should be able to have your lights on, AC on, idling in drive, and still raise and lower the windows without stalling or even stumbling.


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## speedman (Feb 4, 2005)

On mine the alternator was replaced a year ago, so it seems to be working fine.


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## Redcar (Aug 4, 2005)

*Problem still not fixed*

I sent the car to Nissan dealership for diagnostic and was told that everything was fine with the car except that fuel system was dirty, throttle body had carbon built up and the base idle was too low. I had the fuel system and throttle body cleaned and base idle adjusted to manufacturer standard. The dealership cleaned the fuel line using a pressure gauge and added BG44K to the tank after the service. Now the car runs very smooth and is very powerful.

However, the idle problem is still unresolved. In addition, one more problem comes. Since the dealership raised the base idle a bit, the car idled at around 800~900rpm before a red light. If I put the car to "P" at stop, sometimes the idle jumped to 1500, very weird if I gave some gas the idle dropped to ~800 again. It sounds to me that shifting to "P" has left the throttle position valve open resulting the high idle. I know this is abnormal but the dealership told me that because the idle came to normal after I gave some gas, this should not be a problem.

I am very tired of this problem and am thinking to get rid of this car. You guys have any idea if I have missed any part in fixing it? So far I have spent $500 on it - changed spark plugs, wires, rotor cap, fuel injector, air filter, fuel line cleaning, throttle body cleaning, and dealer diagnosis.


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## jserrano (Oct 27, 2004)

The low idle drop because of electrical power draw is due to the alternator. It is called magnetic drag and basically caused by a braking action on the alternator rotor which is felt back on the crankshaft through the drive belts. This is somewhat normal and I understand that some types of alternators, like the high output amp types, doesn't seem to manifest this "problem".

The best you can hope for is a weak grounding somewhere that aggravates this.


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## KA24Tech (Feb 2, 2004)

Make sure the A/C or defroster is off and see what the idle does. 
I also agree that it could be a poor ground as well. Check all the connections to the battery and the engine for anything loose or corroded.

Troy


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## rps180 (Aug 20, 2005)

Another known problem with this series Altima is a bad intake manifold gasket. A quick way to check this would be to start the car and leave it in idle. Then using brake cleaner, spray along the area where the intake manifold bolts to the head. A bad intake manifold gasket will cause the idle to temporarily go up since it will suck in the brake cleaner.
Don't forget a carboned/gunked throttle body will have the same effect.


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## Redcar (Aug 4, 2005)

*Connection sounds ok*

The battery terminals and engine connections sound fine. The battery voltage is 12v at cold and 13.8v when engine is on. Is there a good way to check poor grounding?

Another intermittent problem arouse after TB cleaning. Occasionally when I stopped the car with transmission at "P", the idle jumped to ~1200 from ~800. I could feel a shock in the car due to this jump. However, if I switched the transmission to "D", the idle could get back to ~800. This problem is not solid. What are possible causes to it?


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## KA24Tech (Feb 2, 2004)

back the idle screw back down because you cleaned the TB air bleed very well it sounds like.
To check the grounds hold the negative meter probe on the battery and toch the grounds on the engine and body with the positive lead. Turn the scale on the meter down to a volt if it is analog. The readings should be below 0.2 volts or 200 mv.

Troy


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## Redcar (Aug 4, 2005)

The voltage diff between battery negative and engine ground is about 15mV, so I think the electric system is properly grounded.

What else do you guys think might be the cause to the idle problem? It is really a headache to me.


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## KA24Tech (Feb 2, 2004)

Check the intake manifold gasket by spraying carb cleaner around where the intake connects to the head. If the idle goes up then there is a problem with that.

Troy


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