Throttle body/Maxbore question

I just got my TB back from Maxbore. It is much improved. Wondering though, if it should have any light showing through? It is similar on the top of the butterfly. I am ok with it not being perfect if this is the norm, just double checking. I am sure he does the best he can with the state he receives it in.

 

If that's how it came back from Maxbore, I'd say you're good to go.

 

Your good.

 

Curious, do you have a before picture? I recently pulled my TB off to replace the TPS. Here's what it looked like for reference, 173k miles:

 

That looks about how mine was.
I have another pic on here somewhere & it seemed a little worse than this pic. I haven’t mastered the one handed cell phone pic taking

 

It’s normal to have a small gap like that before and after rebuild.

 

K. disregard the below post. I guess it just has to have give, screw stays with it whilst the "dash pot" should be responding to the vacuum.

Also, there’s no space between the adjuster screw for the “vacuum actuated dash pot (aka Damper)”, as Maxbore put it. I’ve been informed on here that mine was not a dash pot.
Shouldn’t there be a minuscule (.003?) amount there? Or does mine set right up to the adjuster screw?

 

Right. Kinda just figuring this out. His instructions were to make sure there was vacuum at the dash pot/damper, which would close the butterfly all the way on startup. Mine had no give to it at all, meaning when I forced the cable wheel to fully close, the butterfly stayed where it was, which would cause undo stress to the butterfly. It looks as though the damper screw was messed with. Did I do this? Maybe. Anyway, I set it back to have the yellow marks/threads line up, so now there is some give at the damper.

 

Let us know how it works out.

 

Will do. Per usual with me, it got more involved. In whatever number ditch effort to help the idle, I had indeed messed with the adjuster screws. So I set to getting them back to good. Then remembered that I had managed to strip where the nut goes on to the cable wheel. At the time I just made do. Now I figure I should get my hands on a die set, especially since he (Max) had it apart for the 1st time in 21 yrs & he put a spacer in. Plus, I had surgery recently. I ended up with a pinched nerve in my arm, so I'm attempting to listen to it. Very difficult to do, however I know I don't want it getting worse & it was feeling a little taxed.
Anyway I'll be back at it tomorrow. A neighbor has a tap & die set which he will kindly lend me.

 

Not sure how it works with your TB (elctronic?). I mean I imagine it's the same principal, just happens differently. The butterfly is supposed to be open a pinch. Then on startup, it closes. Mine is done through the dash pot/dampener. There's vacuum applied to it & does it's thing.
If I want to do this manually, I turn the linkage wheel back because if it's set right, there will be just that much room before it hits the stop screw to totally close the butterfly.
(Someone please correct me if I'm wrong).

Point is, just looking at it without manually closing the butterfly, you're not getting the whole story. The 1st gens have an issue with the butterfly moving over, so one side gets more worn. Yours looks pretty even. However, that's a bit of miles.

I'd close it & then see what light there is. Also, if it's rubbing or feels like it's sticking when being opened/closed. Should be a fluid motion....

A few minutes later - On 2nd look, is that already closed? Seems so straight up & down....

 

I set the screws back to where they were & this is the result with no vacuum.


Then, theoretically, applying vacuum will close it all the way. Yes?

 

Yes, if it is being held open by light spring pressure, not stuck or prematurely hitting an improperly set stop screw.
That is the action of the THROTTLE OPENER, the function is to give the engine a little more air at starting only. The dashpot is a completely different thing and only "slows/damps" the last few degrees of throttle closure. The dashpot (front of TB) does not have any vacuum connection and should not prevent the throttle plate from closing, ever.

If you want some refresher posts covering this and some related stuff use this search criteria to see it covered from several angles. Some of your previous posts will come back.
Of the 45 or so returns, focus on the posts with the bold throttle opener.
Use TW search not Google.

 

I am going to look at the posts. However before I go touching anything to do with any screws, would I be correct in thinking that the 9-11 at idle is when the truck is at a healthy idle? In other words, mine is at 9.8 with an idle of 1,000-ish.
That’s just the starting point & the fun never ends. When I snapped the throttle to 2800, we only went to 10.2…. Not sure what it should have been, but I’m guessing 10.2 is a leeettle low….

 

The "9-11" spec is the angle of the throttle plate with vacuum on the throttle opener. In this condition the throttle linkage is against it's stop screw and the throttle opener is completely out of the picture. The throttle stop screw should be set so the throttle plate is closed with vacuum on the opener or held closed with light finger pressure (overcoming the TO spring). In this case "closed" means the throttle plate is as closed as it can get without actually touching the wall of the body. This prevents the plate from getting stuck or sticking (wedged) in place. That is the only job of the throttle stop screw, it is not intended to have anything to do with idle speed (like on a carburetor). A "catch 22" arises as moving the stop screw will also change the idle TPS reading, possibly why the spec has an acceptable range.

IIRC we had some confusion about where the stop screw was located, I don't remember if that got cleared up. The million dollar question is "how much gap should the plate have when its closed". There is no official spec for this. It just should not bind or stick with just a fuzz extra for reliability and to allow for a little wear.
Understand that the idle air control valve under command of the ECU is responsible for achieving the correct idle RPM by regulating the air bypassing the throttle plate. The IAC is capable of supplying/restricting enough air to compensate for minor variations in the small bit of air that does get by the throttle plate and to some extent small vacuum leaks in other spots. If a vacuum leak gets bad enough and beyond compensation by the IAC it can raise idle speed, among other things.

Now your issue of relatively no change in the throttle angle when you "snapped" the throttle. Is the TPS plugged in? It could be as simple as your reader not sampling fast enough to catch a quick blip.
In theory if the ECU is getting other inputs like from the MAF, crank/cam sensors and RPM it should say to itself "Hey, looks like we are way over idle speed, what's up with the throttle position reading?" and set one of the TPS trouble codes. The FSM has the resistance specs for checking the TPS in the open and closed position. The change should be smooth and steady as the sensor travels through it's range. No skips or dead spots.

One would think/hope Max Bore calibrates essentially a new (larger) bore diameter, throttle plate and stop screw setting while retaining the 9-11 sensor reading. Your reading suggests at least the TPS signal (idle) is within range.

Carry on

 

thank you! I suppose if one used voltage as a measuring stick, that could work? Mine reads at .75 closed. However if I close the gap due to the throttle opener, it’s at .51. Ideally, it would be .55 = .1 x 5.5 or 10%.

The .51 I am set at now was just from me closing it as much as I could. This using voltage just occurred to me this morning. Point is, now that I have seen your post, I realize mine is set too closed both due to the info you imparted & potentially, the voltage aha!

Also, being that it would be a challenge setting it using the ECM connectors, one could backprobe the connection itself. That way you’re right next to the throttle body.

 

& yes, another question -
Again, 3 wire type TPS

When I check VTA/E2 at the ecm, I get readings

However, when I check VTA/E2 harness side, disconnected, I get nothing.

Even though this isn’t something that is always included in testing, I just do it. It means to me that all is good from ecm to harness connector.

I could backprobe it, however now you’ve added vc into the mix. & I suppose, unless necessary, we don’t wanna go jabbing pins in the back of the connectors if we can help it.

Anyway, is there something different about this circuit that would cause there to be no voltage unless connected?

& as a comparison, I recently tested my vapor pressure sensor which is 4.9 (PTNK/E2). I did get a 4.9 harness side whilst disconnected. This is also a 3 wire type with a range of readings.

 

I'm a little lost with the "checking by voltage" thing.
As far as the harness vs ECM. The harness should be conveying anything it sees at the ECM. You should be using the same ground point you used at the ECM when checking at the harness end. Delicate microprocessor systems sometimes have an "in house" ground point so signals referenced to ground have a uniform comparison point. Never the less at some point closer to the battery all grounds are connected together or "bonded" as they say.

I would be setting the throttle stop by eye/feel then verify the idle TPS is in range and hope for the best but it sounds like it already is. IIRC the TPS signal can be read with a reader/scanner, ignition on/engine off and should change as you open and close the throttle by manipulating the bell crank at the TB.

I would also be looking at why the idle is 1K, should be around 750 in neutral/AC off. Might try giving this a shot. Assuming no vacuum leaks, engine running and warmed up, back off the stop screw exactly one turn (so it can easily be returned to it's current spot) and see if the idle speed drops. If it does there may be too much air getting by the plate and the IAC can't deal with it. If that's the case it will be a balancing act to get idle speed and TPS in range.

 

In addition to this, I'd also suggest making sure the throttle cable itself is not too tight. Mine was ever so slightly too tight, and it resulted in a higher than expected idle. There is also the opposite- where the cable can be too loose, and when you hit the pedal it doesn't open the throttle until a noticeable time later and with a bit of a jerk. Goldilocks- gotta get that cable adjusted just right.

 

This is my confusion as well. Or at least I think we’re on the same page.

Per FSM instructions

VAT/E2 at ecm - key on - check voltage fully closed & fully open. I pass.
Then when I check the TPS harness, disconnected, key on
VAT/E2 - 0.00 - shouldn't I get a, as I have now learned to call it, ghost voltage?
So for ha-ha’s
VAT/VC - 4.69
E2/VC - 5.05

I decided to back probe the tps connected connector & this is when I did get what I got at the ecm for VTA/E2.
So, disconnected, at tps harness, key on = 0.00
Connected, back probing at tps harness & evm I get passing readings.

Maybe some types of sensors do not produce a ghost voltage? I had just checked my vapor pressure sensor & did get 4.95 for PTNK/E2 at the VPS disconnected harness.

Referencing colors just in case that’s in question.
LG - E2
Y-R - VAT
G-B - VC

Unfortunately my scanner insists my truck be on in order to connect. Bluedriver
Wish I had realized this was a drawback. I would have opted for something else.