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Discussion Starter #1
Over the weekend, I decided to pull out my rotary tool, pull off my throttle body, and port and polish it myself. I've seen a lot of people installing ported and polished throttle bodies on their Commanders, but there aren't many write ups on how to actually port and polish one, so I thought I would make one here. Note that I'm not using the best tools for the job, but I'm using what I've got. Here's the process.

Step 1: Get the tools. I ended up using a Wen rotary tool to do all of my work, with a number of different accessories. I used a drum with 60 grit, 120 grit, and 240 grit sandpaper. I also used a 240 grit sanding wheel. Finally, I used some polishing compound and a wool polishing wheel to finish everything off.


This is what the throttle body looked like initially. As you can see, the inside is pretty rough, and there's a part sticking out in the middle. You'll want to grind most of this away, but it's important that you leave the section where the plate makes contact pretty much untouched, as you don't want to leave the throttle body unable to close. I would recommend removing the plate if you can, but I stripped the heads of both screws holding it in so I didn't bother with that.



The first step is to use 60 grit to sand away everything you don't want. I only took off about a millimeter all around, but there's room to take off more. I've read that any more than an 83 mm opening won't help because that's the size opening the engine block has, but I'm not sure about the accuracy of that statement. You can see the spots I left untouched.





After you feel you've gotten most of the material ground away, hit the throttle body with some 120 grit. This will start to smooth things out.Then, to finish smoothing it all out, hit the throttle body with some 240 grit. It can be hard to get every area with the sanding drum, which is where a sanding wheel can come in handy. I would also recommend using sandpaper in the future for the really hard to reach spots. Next, it's time to use some polishing compound and polish everything properly. It should feel smooth after this.



After hitting it with some throttle body cleaner to get everything cleaned up, it's time to reinstall it. Assuming you already have the air box off because you had to remove the throttle body, it's a pretty simple process. Just put the bolts back in and connect the harness.


I didn't put the intake back on yet because I wanted to make sure everything still worked, so I connected the battery, turned the key, and started the Jeep up. It sounded great, then started to idle roughly. Disconnecting the battery again fixed that problem, or so I thought. I threw everything back together. Still a good looking engine compartment.


After putting everything back, I drove around for awhile, at which time the engine light came on.


I was worried I damaged a sensor somewhere, but I pulled the codes using the key toggle trick and it threw P0171 and P0174. These codes mean the engine is running lean, and I figured it was because the computer couldn't figure out it was getting more air. I disconnected the battery again and made sure the cat was fully discharged, then reconnected it again. The check engine light disappeared.

However, driving it around wasn't perfect. It still had a bit of a rough idle, and occasionally the RPMs would jump. I attribute this to the computer taking awhile to learn the new throttle body, because the cat is running well now.

As for gains, I can tell you that this isn't a miracle worker. I can definitely feel a bit more throttle response, but it's not too great. As for gas mileage, it seems to have improved, but I can't be sure yet. In a couple weeks, I'll be taking a 150 mile road trip that the EVIC normally says I average around 15 mpg on, so I should be able to tell you how much it's improved after that.

As far as this mod goes, it's not too difficult. I'm no mechanic, and I'm definitely not the best with a rotary tool, but it didn't seem too bad for me. It was definitely time consuming, taking me almost 4 hours to port and polish the throttle body. However, in doing it myself, it cost me almost nothing, and with that price I think it's well worth it.
 

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The throttle body relearn procedure is as follows:

1. With the vehicle off and in park, put the key in and turn it to the ON position (Not start)
2. Slowly press in the throttle pedal to WOT, and slowly release
3. Repeat step 2 for a total of three times
4. Turn ignition to OFF

My initial impressions leads me to think that there isn't much power to be gained through this bore-wise, because you're leaving the area where the throttle plate seals to the throttle body untouched. Not a bad idea, but you're leaving that bottle neck in the system. The air will speed up to go through the center section and then slow down on the other side of the engine before entering the engine. This change in air speed may be the primary reason for the engine needing to relearn the throttle input. Any gains you would see through this would be from the surface finish rather than the increased bore. The fact that you got some throttle response out of the project speaks to your finished product, however.

If you want to take it a step further, I think there may be a little more yet to get from an ultra smooth finish. You could hit up the auto body section and get some 400, 600, 800, 1000, and 1500 grit wet sand paper and hand sand the surface to a matte finish, from which you should be able to get a near-mirror finish with aluminum polish on your dremel or a drill attachment wheel polisher, depending on the amount of work you put in.

Nice write up. :)
 

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The throttle body relearn procedure is as follows:

1. With the vehicle off and in park, put the key in and turn it to the ON position (Not start)
2. Slowly press in the throttle pedal to WOT, and slowly release
3. Repeat step 2 for a total of three times
4. Turn ignition to OFF

My initial impressions leads me to think that there isn't much power to be gained through this bore-wise, because you're leaving the area where the throttle plate seals to the throttle body untouched. Not a bad idea, but you're leaving that bottle neck in the system. The air will speed up to go through the center section and then slow down on the other side of the engine before entering the engine. This change in air speed may be the primary reason for the engine needing to relearn the throttle input. Any gains you would see through this would be from the surface finish rather than the increased bore. The fact that you got some throttle response out of the project speaks to your finished product, however.

If you want to take it a step further, I think there may be a little more yet to get from an ultra smooth finish. You could hit up the auto body section and get some 400, 600, 800, 1000, and 1500 grit wet sand paper and hand sand the surface to a matte finish, from which you should be able to get a near-mirror finish with aluminum polish on your dremel or a drill attachment wheel polisher, depending on the amount of work you put in.

Nice write up. :)
Sounds just like the OIL change light reset procedure.
 

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That would be a very strange way to reset an oil change light. My oil change reset is done through the EVIC menus.
Off on a tangent, but:
It's different for 08+
For 2008 and up models.

Engine Oil Change Indicator System

Oil Change Required
Your vehicle is equipped with an engine oil change
indicator system. The “Oil Change Required” message
will flash in the EVIC display for approximately 10
seconds after a single chime has sounded to indicate the
next scheduled oil change interval. The engine oil change
indicator system is duty cycle based, which means the
engine oil change interval may fluctuate dependent upon
your personal driving style.
Unless reset, this message will continue to display each
time you turn the ignition switch to the ON/RUN
position. To turn off the message temporarily, press and
release the MENU button. To reset the oil change indicator
system (after performing the scheduled maintenance)
refer to the following procedure.

1. Turn the ignition switch to the ON position (Do not
start the engine).

2. Fully depress the accelerator pedal slowly three times
within 10 seconds.

3. Turn the ignition switch to the OFF/LOCK position.

NOTE: If the indicator message illuminates when you
start the vehicle, the oil change indicator system did not
reset. If necessary repeat this procedure.
 

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I did something similar to my old Camaro way back in the day, Knife edged the plates (dual TB) and cleaned up the intake manifold burrs and opened that up as well. Made a big difference in conjunction with siamesed runners (TPI 350).
 

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Discussion Starter #7
My Jeep has learned the throttle body by now, so no need to go through the step process you stated. Also, I'm not sure if you can see it in the picture, but the throttle body makes contact with the plate at a slant, so there isn't simply a vertical ring of extra material. It's distributed out along a slant, so the effect of that extra material is lessened, still giving me more throughput in the throttle body. In the future, I will probably try to clean it up even more and give it a proper polish, but for now I was just working with the tools I had.
 

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My Jeep has learned the throttle body by now, so no need to go through the step process you stated. Also, I'm not sure if you can see it in the picture, but the throttle body makes contact with the plate at a slant, so there isn't simply a vertical ring of extra material. It's distributed out along a slant, so the effect of that extra material is lessened, still giving me more throughput in the throttle body. In the future, I will probably try to clean it up even more and give it a proper polish, but for now I was just working with the tools I had.
Looks great. :respect:
 

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Off on a tangent, but:
It's different for 08+
Interesting, and indeed strange. I've seen the aforementioned throttle body relearn procedure outlined multiple times for the hemi, so perhaps it performs a double duty in '08+? I'm stumped.
 

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The PCM needs to learn the throttle position values (either from TPS sensor or gas pedal for Drive-by-Wire). The PCM needs to learn the volumetric efficiency values of the engine, this it concludes from closed loop operation with the O2 sensor, i.e. the corrections it needs to make to get the correct AF ratio are the results in variances in the VE. Another way to look at it, the PCM is calibrating the system constantly.

Keep in mind, when you dump the volatile memory of the PCM (reset it), it needs to relearn and recalibrate, this is sometimes called quick learn mode.

Pressing the gas pedal all the way down, just tells the PCM what are the resistance (voltage drop) values of the potentiometer in the TPS or the gas pedal (DBW). It will get them during normal driving, but if you made a big change, like installed a new Throttle Body, TPS or DBW gas pedal, doing the procedure will help the PCM learn it right away and thus save some poor driving until the PCM learns it. Since you didn't change the TPS or DBW Gas Pedal, there was no change for the PCM to learn with the procedure someone quoted in an earlier post.

BTW, the oil change message reset, that only works if you have a message warning to change the oil, doing the procedure when you do NOT have the message will NOT do anything. So doing the procedure without the oil change message just calibrates the throttle position sensing. If you reset the oil change warning, maybe it will recalibrate the throttle position sensing as well, no big deal, it never hurts to recalibrate as long as you do it right. And even if you do it wrong, the system will correct itself while driving.

Looks like your TB is DBW anyway, so its the gas pedal that the PCM is measuring and calibrating itself to.

The changes you made to the TB will effect airflow under different conditions, loads and rpm's. That is VE, doing the procedure quoted won't calibrate the system for those changes in VE. You have to drive around in various conditions and loads, throttle positions in closed loop, i.e. warmed up, before the PCM made adjustments (calibrated) to the changes. You didn't do anything to change the throttle position sensing (i.e. change the sensors).

That is why you didn't miss anything by NOT performing the stated procedure, and you did see some warnings/symptoms of the Engine Control system being out of calibration, and after some driving it seemed to calibrate itself and perform better.
 

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Discussion Starter #12
Update to the mod:

After a few months of use, I can see marginal improvements in gas mileage. However, a word of caution. When cleaning my throttle body, I sprayed the cleaner directly onto the throttle body because I was unaware of the electronics. Now my TPS sensor is failing. Therefore, to anyone thinking about cleaning or porting their own throttle body, I recommend that you simply spray a cleaner onto a rag and then wipe down the throttle body.
 

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The TPS mounts to the outside of the throttle body and does not come in contact with the inside of the tb. The idle air sensors inside the tb and should not fail by using the cleaners. You can actually remove it and spray out the carbon to help clean up a rough idle. Or replace it for around $25
 

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Discussion Starter #14
Correct, spraying into the throttle body should cause no problems. The issue I've run into is that I believe I allowed overspray to come in contact with the outside of the throttle body and into the electronics where the TPS does sit.
 
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