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Tencent's ten-cent fix
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deprivation
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PostPosted: Tue Oct 23, 2007 3:05 pm    Post subject: Tencent's ten-cent fix Reply with quote

I have been having odd running issues: weird idle, a bit of pinging, missing, etc.

So, I did Tencent's JB-Weld throttle fix. It's very easy to do and I will post pix next week. I also made some additions to the procedure such as JB-welding an allen wrench to the TPS cam so it's easier to adjust in situ and adding silicone gaskets to the throttle shaft.

I also re-set the timing by Tencent's method, which is, very roughly, set the timing on a nice hot engine to 40 degrees total advance, which is as he notes about 2" clockwise from the v-notch. Mine was off by about 3-5 degrees and my intermittant pinging went away.

It still runs rough with the o2 sensor connected and NOW my oil light buzzes and the OX/BATT light stays on when I start the engine. Blipping the throttle makes the OX/BATT light go out but for some reason my oil press is in the crapper.

I ordered a new pressure valve spring, senders and for good measure, a HD oil pump from BD.

Just keepin' ya posted. Anyway my point is: the advice here is pretty f*ckin' good.

THANKS TO EVERYONE WHO'S HELPED ME GET THIS FAR!!!!!
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psych-illogical
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PostPosted: Tue Oct 23, 2007 3:48 pm    Post subject: Reply with quote

Glad to get a second data point on the JB weld TB fix. I was lookin' at my TB last weekend and you could drive a truck between the bore and the throttle plate. The shaft seemed nice and tight but there's a lot of wear of either the plate or the bore in the TB. I'm anxious to see any pix you took. I've been following the other thread that's been going on about the TB stuff and one thing I've noticed is that my idle bypass screw has little to no effect on the idle speed. Not surprising considering the amount of light I can see when I hold the TB up to the light.

Not sure about your OXS/Batt light issue. Does it stay off once you've blipped the throttle? Mine does the same thing every once in a while and it stays off after I give it a little blip. I've learned to quit worrying about it.

My OP wasn't exactly in the crapper but sometimes got low enough for me to worry about. The HD oil pump plus the addition of a cooler has made all the difference in the world.
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Yellow Rabbit
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PostPosted: Tue Oct 23, 2007 5:16 pm    Post subject: Reply with quote

Where did you get the throttle shaft gaskets? Do you have pics?
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deprivation
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PostPosted: Tue Oct 23, 2007 8:07 pm    Post subject: Reply with quote

psych-illogical wrote:
The HD oil pump plus the addition of a cooler has made all the difference in the world.

I may PM you regarding the pump replacement. I've never done that job before.
psych-illogical wrote:
Not sure about your OXS/Batt light issue. Does it stay off once you've blipped the throttle?

Yep. But it picked a bad day to come up, ya know?

psych-illogical wrote:
one thing I've noticed is that my idle bypass screw has little to no effect on the idle speed.

Exactly. That's what got me seriously looking at the Tencent TB fix. I'd have the thing all the way in and maybe I'd be able to knock a little off the idle but that's it. Now I can practically stall the damn thing out.

The key to the JB weld fix is to get a good sticky layer of grease on the plate and shaft and very carefully remove any traces of greace from the TB throat. Mix up the JB ahead of time so it's thick, too. And finally, be prepared to sand away about 70-80 percent of the JB weld.

Yellow Rabbit wrote:
Where did you get the throttle shaft gaskets? Do you have pics?

You can still get the gaskets at VW america, supposedly. I made mine with black silicone ATV. I've got a million job things right now but I will post the TB fix procedure in the near future.
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tencentlife
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PostPosted: Tue Oct 23, 2007 8:55 pm    Post subject: Reply with quote

Do it up, dep. Sounds like you got it right.


Since I did this:
Image may have been reduced in size. Click image to view fullscreen.

Added the arly dual-switch brackets to my late TB,

I did this:
Image may have been reduced in size. Click image to view fullscreen.

Added a new bearing plate to the underside where the single-switch plate used to attach. The worst shaft wear is in the lower bearing, which has a much shorter drilled hole to bear the shaft, which is of course one of the main reasons the late TB switches get so ornery. This plate goes right over the original seal, but has a new drilled hole that is a perfect fit for the shaft. Nice and straight.
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psych-illogical
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PostPosted: Wed Oct 24, 2007 9:15 am    Post subject: Reply with quote

One thing I've not yet seen mentioned in any of these TB posts are the little screws that hold the throttle plate in. I'm not close to my van at this moment (I'm actually being very unproductive at work) to be able to check but I would assume that the screws are peened to prevent them from backing out? I know that this is an often dicussed point for the throttle plate on the BMW motorcycle forums. It'd suck to suck one of those screws down into your motor. Rolling Eyes I'm guessing that, in order to replace the throttle shaft bushings and/or seals, that the shaft needs to come out and consequently, to remove the shaft, the throttle plate needs to come off? On my motorcycles I have to grind off a little bit of the threaded end of the screw (the peened end) with a dremel to be able to get the screw out. Is it the same with these TBs?
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iceracer
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PostPosted: Wed Oct 24, 2007 9:19 am    Post subject: Reply with quote

The throttle plate screws are Torks. I removed mine several times when rebuilding. Just put them back in and snugged them down. Now I wonder if I should have locktighted them in. HMMMMMMMMMMMM
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tencentlife
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PostPosted: Wed Oct 24, 2007 11:15 am    Post subject: Reply with quote

Yes, they are tiny Torx screws. They aren't peened to speak of, I think a little Loctite was used and would be a good idea. They have to come out to remove the buterfly, etc. As for being sucked into the engine, I don't think it would be a big deal. I've seen engines gobble up little fasteners before, hardly anthing is as hard as the stellite valve seats and valve facings, so stuff just gets mashed and spit right out the exhaust pretty quick.
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tclark
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PostPosted: Thu Oct 25, 2007 9:55 am    Post subject: Re: Tencent's ten-cent fix Reply with quote

deprivation wrote:


adding silicone gaskets to the throttle shaft.


I also have a TB issue
http://www.thesamba.com/vw/forum/viewtopic.php?t=260502&sid=eb1f8c87912c969febe0e456f4afffa8
but fluked out on parts hunt found this
http://members.shaw.ca/trclark/throttle/1_9TightThrottleBody.jpg
from what I can tell this one is dam near perrrrfect
but to reduce wear in the future adding silicone gaskets top & bottom on the shaft seems it would reduce wear & allow simple replacement of the gaskets when wear did occur saving the tb body & the butterfly ...
is that the assumption here ??
ps what size silicone gakets did you use http link ??
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deprivation
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PostPosted: Thu Oct 25, 2007 11:03 am    Post subject: Re: Tencent's ten-cent fix Reply with quote

tclark wrote:
ps what size silicone gakets did you use

I sort of made the gaskets. I built on Tencent's JB Weld TB fix: apply grease to surfaces that you don't want stuff to stick to. So, I applied a film of grease to the shaft and used a q-tip soaked in Brakleen to carefully clean the surface of the existing TB gasket. Then I used a small wooden dowel to apply silicone ATV around the base of the shaft/gasket.

The ATV cures in a day. I then carefully slipped an exacto between the shaft and the new silicone to make sure it didn't stick to the shaft. Instant gasket! It's not as tough as the original rubber gasket but engine vacuum will hold the silicone against the shaft.

I called my VW dealer and they said the could order new gaskets for $6 each but I'm too cheap to drop $12 on that.
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PostPosted: Thu Oct 25, 2007 11:05 am    Post subject: Reply with quote

You mean the shaft seals? They're not going to do anything to alleviate wear. Bronze bushings would be the answer. The seals actually don't do a lot anyway, you can have worn bearing areas around the shaft, and the amount of air leakage is much too small to have any effect on idle. Vac leaks really need to be pretty huge to throw off idle if the other feedback systems are working properly. To see what I mean, take a good idling motor and pull off the vac line to the fuel pressure regulator. Idle goes up slightly for a second, until lambda and the idle speed controller bring it back into range. So new shaft seals are nice but I wouldn't sweat them. What I would sweat is excessive wear in the shaft bearing areas, and the poor fit of the butterfly when closed.

The worst troubles that result from extreme TB wear are these:

1. On Digifant single-switch units, the worst wear is on the lower bearing bore and shaft, which is stupidly half the area of the top one, so that makes the actual cam position when the throttle closes erratic. It won't come to rest in the same exact position every time, and engine vacuum and heat expansion also throw it off. That means you can't get the tiny microswitch to close consistently unless you increase the depth of engagement. If you manage to get consistent switch closure, which you have to have to get consistent idle and activate the idle speed valve controller, the engagement is too deep, and so the switch doesn't open soon enough on tip-in, so the motor bucks when transitioning from idle to power. This wasn't a problem on the Digijet TB's with the dual switches on top, where the bearing wear is much less extreme at the same time the switches are much less sensitive.

2. Butterfly wear is so extreme that plenty of air slips around the edges even when closed, making it impossible to reduce base idle speed to the 850rpm spec. The idle speed controller on Digifant and DIS on Digijet can only add speed to idle, not subtract it, so your idle is always too high even if those systems are working.

3. Air leakage around the forward edge of the butterfly alows air to flow over the EEC control port, generating a vac signal there at idle. That opens the EEC control valve, which vents fresh air thru the charcoal canister where it picks up fuel vapors and carries them to the intake plenum. That means both unmetered air and unpredictable concentrations of fuel vapor are varying the idle speed and mixture. If your lambda and idle speed control systems are working, they will compensate and you probably won't notice. Except when you first start the motor, when the lambda system isn't working yet. The EEC control valve opening will also fluctuate if idle speed fluctuates because air speed across the TB control port will vary. Even if the feedback systems are working fine, butterfly wear here can cause difficult hot-starting and stalling, because the charcoal canister will absorb the most fuel vapors on hot days when heat drives fuel expansion and evaporation in the tank, and the EEC system is adding that excess fuel vapor to the hot-start mixture while the lambda system can't correct for it because it isn't online until a minute or so after startup.

tclark, that TB in your pic looks to be pretty good, much better than your old one for sure. I would get that one in a heartbeat if I were you.
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tclark
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PostPosted: Thu Oct 25, 2007 11:53 am    Post subject: Reply with quote

tencentlife wrote:
You mean the shaft seals? They're not going to do anything to alleviate wear. Bronze bushings would be the answer.

hmm yah ok i think i get it
So you drill out the shaft bore to an over size and put bronze bushings in bore then put the orginal shaft back in and if i still have this 5-10years from now i just replace the bronze bushings if i have wear ..

tencentlife wrote:

tclark, that TB in your pic looks to be pretty good, much better than your old one for sure. I would get that one in a heartbeat if I were you.

yah thats a done deal when i saw that pic Smile
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PostPosted: Thu Oct 25, 2007 12:09 pm    Post subject: Reply with quote

Quote:
So you drill out the shaft bore to an over size and put bronze bushings in bore then put the orginal shaft back in and if i still have this 5-10years from now i just replace the bronze bushings if i have wear


Yes, that's the idea, and that's how quality components are manufactured. Well-made carbs and TB's have bronze bushings from the factory, so they can be reconditioned. They also have miraculous developments like endplay control that prevent a round butterfly from turning into something that looks like the Nissan logo or something.
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PostPosted: Sat Oct 27, 2007 9:25 am    Post subject: Reply with quote

what lubricant if any do you guys use on the throttle shaft where it goes in the bore holes at the top/bottom of the shaft ?

a molly grease like on the cv's or dry film lubricant
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PostPosted: Sat Oct 27, 2007 10:46 am    Post subject: Reply with quote

I use a little Moly, 'cause I have it around. Drylube would be fine, I think.
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