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Hey guys. My 02 crew cab v6 has been giving me an issue lately. It has 215k miles and has been a great truck. However, lately it has been idling very rough when cold. It sounds like it is about to die at 750 rpm. The sound is like it is starving for fuel. If I rev it up it runs fine and it drives down the road just fine with no hiccups. It also seems to run fine at idle after its warm. The problem is getting worse and today I noticed it coughing at 1000 rpm too. The truck had a fuel system service at a dealer at around 130k miles but has had nothing since except for cooling system parts and oil changes. No code has been thrown. Does anyone have any suggestions?

Here is a video of how it sounds.


https://youtu.be/BD5aFyW--4c
 

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Vacuum leak?
 

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I was gong to post this in my old thread (probably still will) but I'm experiencing the same exact issue. Only difference is that it's not temperature dependent. Mine sputters and vibrates at 1k RPMs at all times.

My issue began two days ago after following the Nissan Service Manual for setting TPS. While proceeding I noticed the screw by the Air Idle Screw was bent. I removed the spring assembly, straightened the piece, then adjusted the screw so that the throttle stop thingy was within spec. I then adjusted the TPS per manual using gauges, performed throttle relearn, and it's idled low ever since.

Adjusting the screw by the air idle thingy will raise your RPMs enough to solve your issue, but doing so keeps your throttle body valve slightly open enough to throw off the TPS setting (per the service instructions).

Note: I apologize for my poor description and wording. I'm sitting in programming meeting, so I can't properly label photos and lookup correct part names. Hopefully one of the smarter folks on this site can better elaborate on what I've said here.
 

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I was gong to post this in my old thread (probably still will) but I'm experiencing the same exact issue. Only difference is that it's not temperature dependent. Mine sputters and vibrates at 1k RPMs at all times.

My issue began two days ago after following the Nissan Service Manual for setting TPS. While proceeding I noticed the screw by the Air Idle Screw was bent. I removed the spring assembly, straightened the piece, then adjusted the screw so that the throttle stop thingy was within spec. I then adjusted the TPS per manual using gauges, performed throttle relearn, and it's idled low ever since.

Adjusting the screw by the air idle thingy will raise your RPMs enough to solve your issue, but doing so keeps your throttle body valve slightly open enough to throw off the TPS setting (per the service instructions).

Note: I apologize for my poor description and wording. I'm sitting in programming meeting, so I can't properly label photos and lookup correct part names. Hopefully one of the smarter folks on this site can better elaborate on what I've said here.
That's not the idle air screw, you're adjusting the wrong thing - Nissan says that's should never be touched. The idle air screw has no spring and is a plastic phillips screw
 

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Correct... If you look in the last pic, at the very bottom you will see a small bent screw. That screw is pushing against the plastic air idle screw. Udjusting that will adjust the throttle.
 

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Correct... If you look in the last pic, at the very bottom you will see a small bent screw. That screw is pushing against the plastic air idle screw. Udjusting that will adjust the throttle.
Actually that's not the idle air adjustment screw to adjust idle via the fsm procedure,

The idle air adjustment screw is near the firewall facing straight out pointing towards the driver side fender. Its hard to see and unless you're looking for it, you won't know it's there.

Look on the upper intake manifold, kind of low down there, close to the firewall, with a flashlight and you'll see what looks like a flat plug nearly flush with the intake manifold. It will have a large Phillips head

It is plastic, and if you don't have the right size Phillips you'll strip it out on the first attempt of turning it. If you strip out the Phillips then you have one more shot of turning it with a large flat head .

That's the real adjustment screw and it opens up or closes idle air flow

You can adjust idle with your screw but that's not the right way to do it
 

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As far as not being the right way to do it goes, I mentioned something similar in my initial post. Though not as concise as yours due to my lack of experience I stated that adjusting throttle this way would prevent proper calibration of the TPS (per the service manual) due to the gap difference it causes between the throttle and throttle stop. That being said though, adjusting the small screw I mentioned will in fact increase throttle and solve the sputtering and vibration. Could possibly serve as a simple temp fix.

What the OP (and myself) really need is guidance on how to increase idle without messing with any of the aforementioned parts. My research up to this point has pointed towards there being no other way.
 

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Could possibly be your IAC valve.. try cleaning it and see what that does.. check for stored codes, the light don't always illuminate.
 

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Truck was running fine until I set the TPS per the manual and did the idle relearn. Then it started idling low and vibrating at stops, but drove perfectly.I readjusted everything back to where it was originally and now the idle is twice as bad, and studders when driving. Currently it's not drivable. I'll rip the engin apart tomorrow purely out of curiosity, but more than likely I'll be parting it out for whatever I can get. I hate this f---ing truck.

https://m.youtube.com/watch?v=4K-HbhcoNcM
 

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Removed the TPS. Idles high, but steady, and drives without shuddering, so that's clearly the culprit.
Glad you got it

Did you ever figure out what the factory adjustment of the throttle drum stop screw is supposed to be? The one you're never supposed to touch? I can't find it anywhere and mine has been touched
 

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Appreciate the find Kevin, although it wasn't the Throttle Drum Screw that I adjusted it was the Fast Idle cam screw that I tinkered with.

Over the past few months I've noticed a slight coolant drip under the Intake manifold. It was small, so I paid it no mind. Yesterday I removed the Manifold and plugs as part of my diagnostics. When I removed the #2 spark plug it was soaked in coolant. It sits almost directly below the minor coolant drip. This is observation #1

When I scanned the underside of the manifold I noticed dried coolant on either side of one of the hoses (source of coolant drip). This is observation #2

The leaking hose feeds into what appears to be a hydrolic component. When Coolant is cold (cold start) the plunger is in, as it warms up the plunger moves out and pushes on fast idle component, which in turn decreases the throttle drum. Problem is, I cannot move the fast idle cam by hand like I see people do in videos. This is observation #3

My conclusion is that the fast idle component (spring) is too hard for the plunger to move, which explains why it (the adjustment screw is bent again. Because the area where the screw is is very strong metal, the pressure built up behind the plunger must be extreme enough to leak from the hose, and possibly foul out the plug. Replacing the fast idle assembly is the obvious course of action, but... the assembly is hard to find and the spring for it is discontinued. Go figure!
 

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Appreciate the find Kevin, although it wasn't the Throttle Drum Screw that I adjusted it was the Fast Idle cam screw that I tinkered with.

Over the past few months I've noticed a slight coolant drip under the Intake manifold. It was small, so I paid it no mind. Yesterday I removed the Manifold and plugs as part of my diagnostics. When I removed the #2 spark plug it was soaked in coolant. It sits almost directly below the minor coolant drip. This is observation #1

When I scanned the underside of the manifold I noticed dried coolant on either side of one of the hoses (source of coolant drip). This is observation #2

The leaking hose feeds into what appears to be a hydrolic component. When Coolant is cold (cold start) the plunger is in, as it warms up the plunger moves out and pushes on fast idle component, which in turn decreases the throttle drum. Problem is, I cannot move the fast idle cam by hand like I see people do in videos. This is observation #3

My conclusion is that the fast idle component (spring) is too hard for the plunger to move, which explains why it (the adjustment screw is bent again. Because the area where the screw is is very strong metal, the pressure built up behind the plunger must be extreme enough to leak from the hose, and possibly foul out the plug. Replacing the fast idle assembly is the obvious course of action, but... the assembly is hard to find and the spring for it is discontinued. Go figure!
The fast idle cam has two marks on it, one closest to you on the low side of the cam and one further away on the high side

With a hot engine, adjust the fast idle cam screw so that you are at the line closest to you. The cam should not be touching the assembly because you don't need fast idle with a hot engine

When warming up the engine it should be around the high side mark

I didn't find this info in the manual, I just figured it out myself

I also cannot turn the fast idle cam by hand on mine, I don't have a bent screw either

Does the plunger move at all from a cold start to a hot engine?

The problem sounds like either the plunger is seized or the spring area is seized not allowing the plunger to move

If it's seized in the cold position then there's your high idle problem (if you have one)

If you have a low idle problem then this is not the culprit because with a warm engine the fast idle cam should not even be contacting the throttle at all so even if it were seized on the hot position, it would not cause a low idle problem

The thermal plunger can be bypassed just FYI, loop the hoses together and eliminate all the related hoses and lines from the under side of the upper intake manifold

And then if you're concerned about cold starts I THINK the ecu should richen up the fueling at a cold start even with deleting the fast idle cam. It should see the low intake air temp and low coolant temp, and richen her up just with those on its own without the use of the mechanical plunger. Although I'm not sure how that would translate as far as a smooth cold idle
 

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I'm in agreement with everything you said. What I mentioned previously realates to my coolant leak and possibly the sudden fouled #2 plug causing low idle choking and shuddering while driving. A fouled plug would definitely do it. I appreciate you tested the resistance of your idle cam. Good to know mine isn't harder than it should be. At this point the coolant bypass is pretty much my only option without new parts. Will likely do it tomorrow.

As far as the high idle months ago, I believe that was the TPS. I had it idling and driving decent enough to sell before dialing in the TPS, so I probably should have just left it alone.

And dispite all my frustration-related *****ing, I am learning something new here, so it's not all bad :)
 

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There is no spring behind that plunger; it's a wax element. Depending on the temperature, the wax will melt or cool, causing it to expand or contract, which operates the plunger. If it's seized, which is what has appeared to happen, you need a new wax element. It'll probably be Nissan # 16391-31U00 for a VG33E.
 

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Sorry I must have miscommunicated something. Easy to do given the complexity of our topics. The Plunger, assuming it's not supposed to go all the way in, is working as designed. Also, I was mistaken in my previous comment: I thought the individual in this video moved the Fast Idle Cam easily by hand, but looks like he's actually using a screwdriver for leverage. On top of this it seems his idle cam is bent as well, meaning this is more a matter of poor design rather than me having a unique issue. I will shoot a video on my situation and thoughts later tonight, then post it in here. This way it will be easier to spot any ignorance on my part.

In the meantime this is the video I've been referencing for knowledge on how the FIC works. Start around 3:50.
https://m.youtube.com/watch?v=k_L9DQyI5Aw
 

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Sorry for the delay on the video. I have a couple manifold hoses which need to be replaced before I can reassemble everything. Took what I thought was the correct part numbers from the pipe diagrams to the Nissan dealership, but turned out to be the wrong hoses. Also turned out they were all they had in stock. At $25 for each piece of rubber, I need to figure it out before placing an order online. Why Nissan couldn't just put all parts together according to their assembly is beyond me. Even the parts guy said they suck
 

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