This is related to a few other threads I have going, but with a specific question.

If the Throotle Body is ported (previous owner told me that he ported TB), does the tbs have to be indexed to make up for the new shaft stop position?

If the TB is enlarged, does it allow the plates to move further into the TB at idle, thus allowing the saft going into the tbs to turn out of factory spec at rest?

My tbs's will not consistantly read 0 % closed throttle, or if they do they seem to miss read after light acceleration.

 

If you enlarge the "ports" in the throttle body, you need larger blades..... hence, the "closed" position isn't going to change a lot.

The LT1 PCM looks at the TPS voltage, and as long as its between 0.20-0.90V, sets that as the 0% throttle position (TPP). That's why there is no "adjustment" provided. Some people feel they get better results with closed TPS voltage in the range of 0.50-0.65V, and it you want to adjust it to that, you just need to "slot" the two screw holes so the sensor can be rotated to change the voltage to what you want.

If your TTP reads above "0%" at closed position, first check the linkage to make sure the blades are closing fully, then check the blade "stop screw" to make sure its not out too far to allow the blades to close fully. Finally, check the closed TPS voltage, per the above. You might also want to check the IAC counts to make sure that when you are all done, they are in the range of 20-40.

 

How are the tbs voltage and iac counts meassured? I have two different scan tools, but neither supplies this.

 

Some people shine up the inside and call it ported, not true. IF he ported it, it should be 52mm and have new blades etc. With a properly machined and assembled ported throttle body, you will NOT have to touch anything, bolt on and go.

-Shannon

 

Well, the blades appear to be about 50mm. What is stock.

I cannot get it to start with the maf disconnected and the bellows removed from the maf.

 

I agree, If the throttle body has been properly ported the thorttle shaft position should not change at all.

 

There is no reason to believe that he did it correctly. It just doesn't seem right that the blades would be fully closed at idle. I've always seen them set with a bit of a gap. I''ve been searching for pics of a propertb blade setup.

 

The blades need to be fully closed at idle. The IAC controlls the amount of air for correct idle, so there should be no air leaking by the blades. If you go to 3rd page on my webpage thats in my link you will see some of the throttle bodies I've ported and the way they seal in the bore.

http://www.cardomain.com/id/97pontta

I keep blade to bore clearance between .002-.004 perside, which is less than the thickness of paper. You don't want the blades to hit or bind, just seal very well.

 

fantastic pics. looks like mine issetup right. I am at a loss of what is wrong.

 

It should look like the blades are almost touching the bores.

There are plenty of guys out there that do a wonderful job at porting them. The ones I do are direct bolt-on without any ajusting at all, and thats the way a bolt-on should be

 

I have a close up of the TB blade I can e-mail someone to look at. It looks to me like it is totally closed, I can't even slide a piece of paper beteen them and the TB bore. The blades appear to be at a full 90deg angle to the bore.

 

The blades should not be at 90 degree. There should be a slight tip in on the blades. There should be a near airtight seal though. The stock size is 48MM, most over bores go to 52mm unless they waste their time and do 54.5 or silly things like that.

I've been building them for about 3 years now. If someone doesn't know what they are doing, they can completly ruin a good throttle body. I see back yard machinist do it allll the time.

Whats the problem that makes you think the TB is the reason the car won't start ?

-Shannon

 

It will start and run now, when put together, but not correctly.

Orginally, I got a bad tps code and the car was slightly bucking and running badly, getting worse everytime I started and drove it. Even after replacing the tps 3 times in 3 days.

Eventually I figured I had bad gas, which I removed when putting in a new fuel filter (BP has a sample of the gas now, but doesn't see how the water got into it from their pump).

But before realizing the bad gas problem, I cleaned the TB, iac passages and MAF, replaced the tps three times and the iac (original checked fine). Now the tps will not line up correctly; it keeps giving a 6 to 15 % open throttle reading at closed throttle (depending on which tps I use).

I noticed that the TB blades closed further after I cleaned them. I'm thinking that this is now taking the TB shaft out of range for the tps and closing off too much air. If I turn the tbs 1/8th in clockwise, the % trottle opening at idle is 0%.

The previous owner said that he "ported the TB," but it looks like he really "polished" it. The original tps works until I hit about 50% throttle, then the tps low voltage code goes off. The new tps works, but sets a low voltage tps code off at about 10% throttle.

I think that the original owner did not set the TB blades correctly, but it some how worked for the last 20K miles with the original tps until I cleaned things up.

So my first step is to set the TB blades in the proper position.

I was told to do this with a rag blocking the iac hole, and adjusting idle to 800rpms. To do this reguires running it with out the MAF, and is not starting without the MAF.

Also, my exhaust used to pop when deaccelerationg (M6), now it is quite when deaccelerating and makes a slight exhaust ping when I attempt to accelerate. I still have not added dry gas and new premium fuel yet, since I'm still not sure about setting up th TB. I'm running it off of fuel I use for the generator, so it is't the proper grade.

Thanks for you interst in helping.