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UPDATE: It turns out my hesitation issue was NOT due to the Throttle Body. I experienced the hesitation issue WITHOUT an engine light. When this happens you have to go to the dealership and have the TCM codes read. If you throw a code in the TCM then you'll have to get the CVT worked on.

This thread will apply if/when you experience the hesitation issue and get a check engine light with a code referencing throttle position or something similar.


Updated as per request from Warhammer. - njjoe




This thread describes how to replace the Throttle Body (TB), Spark Plugs, and the firewall Valve Cover. Refer to pictures throughout the writeup.

My MO is a:
2004 SL AWD
90K miles
K&N Panel Filter
Low PSI AC Line Insulation Upgrade

FAILURE MODE: MO sitting at a red light, engine warmed up and driving for ~30 minutes. Light turns green, push on gas pedal, RPM stay at idle. Completely floor gas pedal, MO slowly creeps forward then races off.

PROJECT TIME: 6-7 hours.

NOTE: This does not address the failure mode that others have seen where you push on the gas pedal, RPM's go up, and the MO does not move. This failure mode typically means the CVT is going bad.

About 2 weeks ago, I experienced the Failure Mode a couple times. Since then, I read a lot of threads about the issue. Every instance referenced having to replace the Throttle Position Sensors (TPS). There are 2 TPS's inside the black housing attached to the TB. Unfortunately, everything comes as a unit so you have to swap out the entire TB to resolve the issue.

I figured at the same time I would do a bit extra work and replace the spark plugs. I've heard that you can keep these plugs in the MO until after 100K miles. I say phooey because no spark plug on the planet will withstand 100K of driving. They start to loose their seals, spark density goes down, etc. I prefer to replace them in shorter intervals.

Of course, while working on replacing the TB and Spark Plugs, I ran into another issue! The drivers side spark plug tube had some oil in it! :eek: The pictures later will describe how this happened but it did not make me a happy camper. :banghead: After doing some research on this forum as well; another reason why I love this forum, I found out that a few members had misfiring caused by swamped plugs. The oil level would eventually reach the top of the plug and the energy would short to the tube. Replacing the valve cover solved this issue.

So...here's my parts list and where I got the parts:
Nissan Re-manufactured Throttle Body (Reliable Nissan)
Throttle Body Gasket (AutoZone)
6qty Iridium Spark Plugs (PulStar)
Firewall Side Valve Cover (Reliable Nissan)
Firewall Side Valve Cover Gasket (Reliable Nissan)

I have a hook-up at Reliable Nissan hence the reason I bought the parts there. He can match and sometimes beat WorldPartsExpress pricing before shipping! :29:

The ultimate goal is to get the upper intake plenum off so we can get under it to replace the plugs and the valve cover.

The first picture (1.jpg) is your baseline. The instructions for the intake plenum and throttle body (1a.jpg) are found in the Service Manual.

Start by removing the air box, hoses, and engine resonator attached to the throttle body (2.jpg).

You'll see the TB exposed with all connectors that surround it (3.jpg). You'll have to remove the hoses and connectors that will interfere with removing the upper intake plenum.

Remove some of the other parts that are holding down the upper intake plenum (4.jpg). You'll have 2 more bolts and a couple more small hoses on the front face to remove.

You have some other hoses and bolts that need to be removed behind the upper intake plenum so you'll have to start removing the wiper arms, the cross member, and other stuff to get to them.

Start by marking where your wipers sit with some blue painters tape, remove the wiper arm caps to expose the wiper arm retaining nuts, remove the wiper arm retaining nuts, remove the wiper arms, carefully pop off the rubber hood seal, and remove the 2 round clips on each side of the plastic finisher (5.jpg).

While removing the plastic finisher, disconnect the windshield washer fluid tubing adapter as shown (6.jpg).

Remove the 3 the wiper motor bolts and disconnect the wiper motor harness (7.jpg).

Remove the 10 bolts that hold down the metal cross member (8.jpg).

Now it's time to start removing the things that are holding down the back end of the upper intake plenum. On the passenger side there are 2 hoses and 2 bolts (9.jpg). The arrows show where the 2 bolts are. The arrow on the lower left points to a connector...this connector is attached to a bracket that has the bolt.
 

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Now it's time to get the old TB off by removing the 4 small bolts around it. It's also time to remove the 2 bolts behind the upper intake plenum, a breather hose, and 2 cooling lines off the TB tube (10.jpg).

With the upper intake plenum off, it's time to get to the radiator bank of plugs. Remove the coils by removing the 3 connectors and 3 bolts (11.jpg).

Removing the coils will expose the spark plugs (12.jpg). Don't forget to put masking tape over the intake manifold! Don't want dirt or other stuff to get in there!

Be sure to keep your coils organized (13.jpg). I like to put them back right where I found them. Also take some time to observe the condition of your plugs. This tells you a lot of what is going on inside your cylinders! You can see that each plug has a brown-ish ring at the top. This is due to failing spark plug seals. Some gas is getting by!

This picture is a good representative of what my plugs looked like (14.jpg). Relatively clean with some carbon buildup. Quite normal looking!

When replacing the plugs, be sure to put some antisieze compound on the threads (15.jpg). I also put some terminal grease on the top of the plug so it's easy to get the plug installation tool off.

After the radiator plugs are replaced, it was time to go after the firewall plugs (16.jpg). To remove the coils, follow the same procedure by removing the coil bolts and plugs. Don't remove the driver side coil plug because it's almost impossible to get to. Remove its bolt only, pull the coil, then pull the plug. Easy!

This is the oil that came out of the firewall driver side spark plug tube (17.jpg)!!!

Luckily, Reliable Nissan had a valve cover and gasket! So instead of finishing up my job Friday evening, I finished up Saturday mid day. OH well...

To remove the firewall side valve cover you have to remove 10 bolts (18.jpg). The center bolt on the passenger side (left) is only accessible by a hand wrench. I had an open end box end wrench that I used to get it off.

I attached the description and specs for the valve covers from the Service Manual. Note that the gasket calls out an RTV Silicone Sealant or equivalent (18a.jpg). You'll use this while installing the new cover.
 

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I also attached what the Silicone RTV Sealant needs to look like to get a good seal (18b.jpg).

The locations where the sealant needs to go is quite logical for the shape of the new cover and gasket (19.jpg).

A close-up view of the sealant (20.jpg).

When you go to install the new valve cover, be sure to put oil on the 3 rubber o-rings as shown (21.jpg). This will allow the rings to slip nicely over the spark plug tubes! Otherwise, you risk introducing the same issue of allowing oil in the spark plug tube. I bet anybody $20 that the original tech that put this motor together just forced the valve covers on without oiling the rubber rings.

After following the reassembly instructions for the valve cover, install the coils, coil plugs, etc etc etc reassemble everything until you get to the point where you can install the new TB (22.jpg). Be sure to check all hoses, clamps, connectors are installed as you work! Otherwise, it will be a PITA down the line!

It's good to note the difference between the new and old TB's. The stamp on the top of the new TB does state it's re-manufactured (23.jpg & 24.jpg). Yes...it has a Nissan stamp! A new TB will cost you over $550 while the rebuilt one I got for about $165. A big difference. The rebuilt TB has a 12K mile or 1yr warranty, whichever comes first.

After you get the new TB on and plugged in, simply reinstall the air box, tubing, and resonator (25.jpg). I also took some time to fix the foam insulator around the intake over the radiator!

To fix the insulation, I used whatever I had laying around the garage. Just some Camper Seal Foam Tape (26.jpg).

I just layered it up until it matched the height of the original insulation. 3 layers (27.jpg).
 

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Here's another snapshot of the finished insulation (28.jpg). Not perfect...but it works!

At this point, it's important to check the motor works before you reinstall the cross member, wiper arms, etc. I performed the Accelerator Pedal Released Position Learning (29a.jpg) and Throttle Valve Closed Position Learning (29b.jpg) BEFORE starting the motor. Otherwise who knows what the ECU might see.

Then I said a little prayer...due to the rework of course :)...and turned over the key. No issues at all! After letting the motor sit for a bit I turned it off and reassembled the cross member, wiper motor, arms, finished, etc (30.jpg).

Finally, I took my MO out for a spin. When I got to my destination, I performed the Idle Air Volume Relearn (29c.jpg). Took me a couple tries but I got it. It's important to have a watch with a second hand with you because timing is key!

Talk about smoooooooooooth riding now. My MO is has its responsiveness back! No more sluggish feeling for sure! You can definitely tell when a motor has new plugs and good working parts. My wife was out running errands on Sunday and she said she got up to 60MPH and didn't even realize it! I drove my MO to a popular fishing hole on Saturday evening and not a hitch! I'm really happy with the results!

Total damage for just the parts was ~$500. This is after the TB core charge is reimbursed, which I will take care of tomorrow. I saved myself ~$750 in labor alone so it was a good weekend. The results, responsiveness of my MO, etc was worth it.

So...questions, comments, concerns, etc are welcome. I hope the pictures and writeup helps!

Enjoy! Do I hear a nomination for making this thread a sticky?!?!? :4:
 

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Definitely worth a sticky!!! Nice work!!!

BTW - Looks like those plug were in great condition. I've driven two cars well past 100K miles with original plugs and no drop in performance.
 

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Thanks!

The plugs did look good all the way around and I was quite impressed by them. I remember working on 80's era vehicles and swapping out the plugs once every other year. Again, older vehicles hence the reason my subconscious urged to swap them out prior to 100K miles. The only thing that really concerns me is the blow-by on each of the plugs. Just shows they deteriorate over their life. Maybe as I work more on late models my opinion of spark plug construction and longevity will change.
 

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Was hoping for some more feedback folks. Maybe the writeup is so crystal clear that nobody needs to ask questions or make comments? In that case...I did one hell of a job... :p
 

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It sure does look bigger doesn't it? Didn't notice it until you brought it up. Thinking it might be the camera angle. Either way I'm not 100% sure...it's good that it works correctly though. :)
 

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100% Sticky, what a great writeup!
 

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Warhammer,

an excellent job! And a great writeup!
 

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SWEET! Another sitcky for the Warhammer! :)

Glad you liked it guys. Hopefully this helps someone in the future.
 

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Thanks!

I think I also might have a loose ground connection somewhere in the dash. Since I did the TB I've only experienced the acceleration issue once. Otherwise it's been smooooooooth. I'm doing research on where the ground points are under the dash. Will probably have to take the entire thing apart to get to them though. Multiple ground points throughout the entire MO so thinking about going after them as well.

It's good to feel the acceleration issue not happening every other day. :)
 

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Awesom write up!!

Warhammer, awesome write up!!

I have a question for you though, My 03 has been hesitating and very sluggish since 75k or so and it just rolled 100k. I have done everything to fix it ( MAF, Throttle position sensor, o2 sensors etc) to no aviail. Did you have the same issue before the gas pedal issue? Ours just did the gas pedal thing about a week ago and I saw your write up and im hoping this is the solution.

Any info you can provide before I pull the trigger on the parts would be appreciated
 

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If you're swapped out the Throttle Position Sensor then you swapped out the TB. Sounds to me like you either have a ground issue or the Accelerator Pedal Position Sensor (APPS) is going bad. There are 2 ground points under the dash; i.e. one on the drivers side and one on the passenger side. I think the passenger side is the one that can come loose and cause a sluggish feeling issue. You have to tear the entire dash apart to get to those so if you do one, might as well do the other.

The APPS is about $150 and is an easy swap. Pick your poison. Either easy swap or difficult rework.
 

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If you're swapped out the Throttle Position Sensor then you swapped out the TB. Sounds to me like you either have a ground issue or the Accelerator Pedal Position Sensor (APPS) is going bad. There are 2 ground points under the dash; i.e. one on the drivers side and one on the passenger side. I think the passenger side is the one that can come loose and cause a sluggish feeling issue. You have to tear the entire dash apart to get to those so if you do one, might as well do the other.

The APPS is about $150 and is an easy swap. Pick your poison. Either easy swap or difficult rework.
My bad, I replaced the APPS already as well as the MAF etc. The symptoms are similar to yours with the exception that the dead pedal has only happened two or three times while the hesitation issue has been consistent for the last 20k miles. By consistent I mean occurs regularly and feels like the the car cant decide to get fuel or not and cuts in and out of power. Mostly little power!:confused:

Are there relearn procedures for the MAF, APPS and O2 sensors?
 

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Discussion Starter #19
Could you describe the hesitation in more detail? Is it EXACTLY like my issue or different?

Mine was simple in that I would have the MO warmed up, sitting at a red light, light turns green, I go to push on pedal...and...nothing. I had to floor the pedal in order to get my MO to move. If your failure mode is something different then we'll have to analyze that some other way. Other forum members have had a similar issue but when they push on the pedal the RPM's go up but no movement. Typically means a bad CVT.
 
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