# 02 Frontier 2.4L idle fluctuation issue



## OE812 (Jun 4, 2006)

I have a hot idle dip on my 2.4L Frontier. In drive, the rpms are around 700 but the idle will fluctuate +-150rpms. I have changed cap, rotor, fuel/air filters, plugs, pcv, throttle gaskets, and cleaned the EGR intake ports. You can actually hear the engine missing at idle.

Any ideas on what could be the problem?


----------



## azrocketman (Oct 5, 2005)

First, look for any vacuum leaks, typically a cracked hose. If you spray carburetor cleaner on a suspect area and the idle speed increases you have found a problem.

Second, try cleaning the Mass Air Flow (MAF) sensor. You can use alcohol, TV tuner cleaner (without lubricant), or spray solvent sold for that purpose. You can use a cotten swap to assist but be careful as the MAF is kind of delicate (and expensive to replace). 

By the way, is the check engine light on? If it is what code is being indicated?

Steve


----------



## OE812 (Jun 4, 2006)

azrocketman said:


> By the way, is the check engine light on? If it is what code is being indicated?
> 
> Steve


Yes it is Steve. I bought the truck a month ago and it has had a persistent P0400 code (EGR insufficient flow). I cleaned the egr ports, replaced the TB gaskets and started performing the EGR troubleshooting. EGR BPT had a busted diaphapm so I put black RTV. That part is costly so I was just trying to save some bucks. 

Is the idle issue related to the P0400? What have you seen as the problem on the P0400 code on these engines?


----------



## azrocketman (Oct 5, 2005)

Most of the EGR related items I've experienced are related to the EGR ports in the intake manifold being clogged. It is also possible that the EGR valve or supply tube are carboned up and restricting flow. You might want to look at Nissanhelp.com for technical service bulletins (TSBs) that are related to the EGR system.

Does the problem occur with a cold engine? Generally, EGR flow is inhibited when an engine is cold.

How many miles on the truck?

Steve


----------



## OE812 (Jun 4, 2006)

azrocketman said:


> Does the problem occur with a cold engine? Generally, EGR flow is inhibited when an engine is cold.
> 
> How many miles on the truck?
> Steve


Cold engine or warm doesn't matter. I have 163,000 miles on truck.


----------



## azrocketman (Oct 5, 2005)

I do not think the EGR is the cause of the idle problem. I'd look for the vacuum leak or cleaning the MAF.

Steve


----------



## OE812 (Jun 4, 2006)

azrocketman said:


> I do not think the EGR is the cause of the idle problem. I'd look for the vacuum leak or cleaning the MAF.
> 
> Steve



azrocketman:

I will check for a vacuum leak. I attempted to remove the MAF from the throttle body but could not. I appeared to be stuck. I see a very very very thin wire when viewing the MAF from the TB top; is this the part to clean? I do not see any debris/dirt on it.


----------



## azrocketman (Oct 5, 2005)

OE812 said:


> azrocketman:
> 
> I will check for a vacuum leak. I attempted to remove the MAF from the throttle body but could not. I appeared to be stuck. I see a very very very thin wire when viewing the MAF from the TB top; is this the part to clean? I do not see any debris/dirt on it.


The wire is the part that gets dirty. It does not take much to affect the MAF's operation; a coating of oil/dirt will do it (oil contamination from K&N reusable filters has been indicated as a problem in the past). Again, the part is fragile so be careful cleaning it.

One suggestion, based on other cars troubleshooting methods is to disconnect the MAF connector. This forces the computer to revert to a backup mode of operation. If the vehicle runs better in the backup mode this is an indication that the problem is MAF related.

Steve


----------



## rogoman (Dec 16, 2004)

Use only ELECTRICAL CONTACT CLEANER or a cleaner specifically made for MAF hot wire cleaning. This is the only thing you should use to clean your MAF. No windex, no carb cleaner, no brake cleaner, no rubbing alcohol, and no Q-Tips.


----------



## azrocketman (Oct 5, 2005)

rogoman said:


> Use only ELECTRICAL CONTACT CLEANER or a cleaner specifically made for MAF hot wire cleaning. This is the only thing you should use to clean your MAF. No windex, no carb cleaner, no brake cleaner, no rubbing alcohol, and no Q-Tips.


I've used an alcohol dampened cotton swab with success in the past but, it does represent a risk because the MAF is delicate. If the OE812 feels more comfortable without any contact with the MAF element then I'd limit the cleaning to just spray type cleaners.

Steve


----------

