# 94 Nissan Altima 230K miles - Erratic idle in morning



## acuevas (Dec 4, 2009)

Hey All,

My Nissan altima has an interesting issue. In the morning when first starting it, the idle is a little erratic after warm up. Then after about 30 mins of driving it seems to 'normalize' itself. However, do get a few misfires throughout the day. Any ideas are most welcomed.

Thanks.


----------



## smj999smj (Jan 1, 2006)

Obviously, condition of plugs, wires, cap and rotor should be taken into consideration. Recheck the base idle setting and adjust as necessary, which needs to be in spec for the IACV-AAC valve to work properly. Sometimes one or more fuel injectors can leak down after the engine shuts off, causing gas to pool in the cylinder and foul the spark plug on start up. I fuel pressure leakdown test would help confirm or eliminate that as a possiblity.


----------



## acuevas (Dec 4, 2009)

Thanks smj999smj,

Here are a few repairs that i have done that may help in honing down the issues. I replaced the sparks plugs, cap and rotor. a fuel pressure test was done and apparently the test was ok. 

I did a code check and was advised that two codes were retrieved:
1. Code 12 - airflow meter circuit. (i cleaned the MAF so this could have triggered the code.) 
2. Code 34 - detonation sensor

I was thinking that it could be the idle air control valve. Can the valve just be cleaned and if so how?

Thanks.


----------



## smj999smj (Jan 1, 2006)

It's possible you could have damaged the MAS by cleaning it, as well. Make sure you erase the codes and if the code returns, it could be something to look into. During the fuel pressure test, did they check for leakdown over the course of 30-minutes, or just confirm that the pressure is within specs? If an IACV-AAC valve is dirty, it can be removed and cleaned with throttle body cleaner. If the valve has an electrical or motor issue, cleaning won't do anything. Also, the location of the IACV-AAC valve isn't in the most convenient place to access, being below the intake manifold. I would try following the factory service manual to adjust the base idle before attempting to clean it. It's also not a likely cause of misfires after warm-up. Something else you may want to check is the intake manifold gasket; try spraying carb cleaner where the intake mounts to the cylinder head while running and see if it causes a "flare" in RPM; if it does, you probably have an intake gasket that has a slight leak, which isn't uncommon on the U13 Altimas.


----------

