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Discussion Starter #1
I'm posting this to get the opinions of the folks out here since I don't have experience with the throttle bodies other than R&R.

Today I was going to install a new/used TB top plate/cover and gasket on my good running Caprice after cleaning the OEM unit. I was investigating an idle issue today. After getting to operating temperature, the idle would wander when I was stopped at a light for longer than a few seconds. The engine would increase and decrease in speed. Sometimes the idle had gotten so low that the engine stopped running.

There were no diagnostic codes.

When I was removing the TB, I noticed that two of the four screws were only snug tight; if that. I'm thinking that may have been the root cause right there.

Since I had a clean nice looking operational TB from KW, I was thinking about replacing the OEM unit with KW's all together.

I was wondering if the difference in size (52 to 58MM) with an OEM engine, with only a few different PCM tweaks would cause any problems?

So if anyone has any thougts on this, I'd appreciate hearing them!

Thanks!
 

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The 52mm should have some tweaks to PCM for trans to shift properly,and under the right line pressure. The 58mm requires the intake openings be opened up as well...
 

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Discussion Starter #3 (Edited)
Thanks for the reply. I've been cleaning up the 48MM yesterday and again this morning with elbow grease & TB Cleaner.

I thought I'd ask you opinion on cleaning the thru bores for the air IN/OUT.

Do you think it would safe to use a brass toothed brush to clean that area?

I ask because I've got a lot of that area cleaned, but there are some stubborn spots from what I can only assume is 176,000 worth of air passing thru.

The brass-toothed brush would certainly make life easier for cleaning the butterflies themselves, as well as the rest of the bore that has yet to clean up.

I've stuck a piece of heater hose in one side to stop the butterfly from closing







 

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When really bad,I'd remove sensors/IAC motor. Then soak for a few days in a coffee can filled with gasoline. Really loosens stuff up. Removing top plate,and bottom casting is also helpful. Throttle body cleaner,and a toothbrush seem to work well. Carefully removing tension off the return spring makes the job easier. Fine/extra-fine ScotchBrite for really stubborn deposits..






 

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JR..

if you change the size of the TB, you will need PCM re-tuned, even from going 52mm-58 or any size other than stock 48mm

you will need to machine the intake manifold to accept the 58...requiring removal (don't ghetto hack a grind job to do it with intake on motor)

there is no performance gain for your mods going to 58. You would be fine with the 48 if that is what the car is tuned for

Use "throttle body" cleaner (read NOT carb cleaner) on TB. You could use a brass, or nylon bristle, brush if you need to

your wondering idle could be a dirty or failing IAC. Since the TB is off, remove it and clean the IAC and the orifice it goes into. DO NOT push or pull on the IAC printle
 

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By memory there is a coating you do not want to remove. This is why you use a cleaner labeled TB safe.

From my limited experience(3) it would be a waste of time to do the TB and not to take apart the IAC to clean it. The top plate may need cleaning.

I just used TB cleaner and dollar store "make up pads"(cloth disks) and "Q tips"
 

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I'd just clean & use the original TB if it's in good shape.
How is the shaft? Any significant slop when closed?
Many times a highish mileage TB has wear and the shaft can get sloppy when closed.
This can lead to inconsistent TPS reading @ idle, and a wandering/varying idle speed.
A TPS can also wear out, and give some idle issues. They're easy to test with a DVM watching ohms readout, or if you have scanner or data cable & software.
 

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Discussion Starter #8 (Edited)
When really bad,I'd remove sensors/IAC motor. Then soak for a few days in a coffee can filled with gasoline. Really loosens stuff up. Removing top plate,and bottom casting is also helpful. Throttle body cleaner,and a toothbrush seem to work well. Carefully removing tension off the return spring makes the job easier. Fine/extra-fine ScotchBrite for really stubborn deposits..
When I replied the first time, I was at a coffee break for myself, and then posted the pictures of the 1/2 cleaned TB. When I went back out to the garage I decided to go ahead and continue with the TB Cleaner with the brass bristle brush.

I assume this is your work in the pictures? Did you decide to use only part of the casting since that's all that's necessary since you did the TB coolant bypass?

JR..

if you change the size of the TB, you will need PCM re-tuned, even from going 52mm-58 or any size other than stock 48mm
Okay, when I got a few things from Kevin at the same time 3.5" MAF also, I had originally planned on only installing these when I rebuild the engine a ways down the road. Since I was going to be getting after the TB, I thought I'd ask the question.

you will need to machine the intake manifold to accept the 58...requiring removal (don't ghetto hack a grind job to do it with intake on motor). Use "throttle body" cleaner (read NOT carb cleaner) on TB
Come on now partner, after reading all my posts and replies over the years you should know me better than that. I'm an anal retentive mechanical designer. I don't take short cuts or do anything half way. Just look at the pictures below.

Use "throttle body" cleaner (read NOT carb cleaner) on TB.
Same as above, but appreciate you putting it out there.

CLEANING

your wondering idle could be a dirty or failing IAC. Since the TB is off, remove it and clean the IAC and the orifice it goes into. DO NOT push or pull on the IAC printle
I cleaned the heck out of the TB Body, and all of the orifices, and the lower casting. I was really impressed how well everything turned out.

I didn't touch the printle at all, as I remember reading thru threads here not to do that. I used a pick and removed any small pieces of gunk on the inside of the spring though.

Everything came out exceptionally well. Sure I took a few hours doing everything, but the results seem to be pretty good. Here's a few pictures of the sinished product.


[url=https://flic.kr/p/24GbAYU]

[img]https://farm1.staticflickr.com/795/27333015798_62cb31b361_h.jpg[/url]

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Last, what is this gasket used for?

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