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Old 08-09-2006, 08:58 PM   #29
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1960 24' Tradewind
santa barbara , California
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Hello lebolewis,

Sometimes these problems are not easy ,and if your not familiar with auto
repairs on these types of systems it can be maddening.I think I would at this point I would run the engine and in the corner of the throttle body there is
the passage that the air is drawn into ,sort of shaped like a small kidney bean
kind of ,spray the WD 40 into that passage ,if then you do not get any idle
speed change at all ,then that means the IAC is commanded all the way shut.
If the speed raises or lowers significantly ,that means the IAC is not commanded closed .The PCM will try to slow the idle down if it can .A scan
tool will show this info ,but you do not have one ,so try that test ,also it
really isn't a corner obviousely on the TBI but it will be the only one there.
.High idle speed can only be excessive air getting in .Don't get into the intake manifold yet.The WD40 will not hurt anything ,so no sweat if it is all over the TBI area.These problems do have to be narrowed down to solve ,I would perform the same test or testing you are doing
as a repair facility myself.Make sure your PCV valve is good ,you can pull it
from the valve cover ,engine on, put your thumb over the valve ,suction
and see if the engine idle goes way down ,some suction at the valve is normal ,as it needs to be there to draw in the crankcase vapors.Way down
means 500 rpm or so ,if not continue with your testing .If your IAC test shows the valve is shut all the way ,then you know there is a vacuum leak somewhere .They do sell a plug tool ,thexton products made it to plug the iregular shaped passage for testing ,don't know today where you can find one
The other option is to take it in to a reputable shop ,does not have to be an
RV place ,and let them tackle it .sometimes it is easier than the stress.
Now all that being said Happy Birthday !!

Scott of scottanlily
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Old 08-10-2006, 05:23 AM   #30
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Fast Idle

Thanks to all of you for your advice and for "hanging in there" with me on this sticky problem.

Scott, I will try spraying the WD40 into the "bean hole" on the TBI. Do all TBI versions have a "bean hole"? If not, then mine is probably one of those. I have a feeling that the IAC pintle is extended all the way shut, one reason I think that is that it was fully extended when I removed it for cleaning. However, closed shut is probably it's normal resting position?

I thought about removing each of the vacuum connections to the TBI and the intake manifold, one at a time, and plug the connection, as a method of elimination. But I immediately realized that the openings are all different sizes and successfully plugging them would be a challenge. That Thexton Plug Tool would sure come in handy right now. I'm still thinking about how I might be able to do that. That seems fairly simple and a sure-fire way of elimination. Oh, will un-plugging any of those do any harm or cause the engine to stall?

I will also check the PCV valve and plug it's port to see if the engine slows to 500 RPMs.

Thanks for the Birthday greeting. .........To be continued.....Bill
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Old 08-10-2006, 05:47 AM   #31
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Fast Idle

Hey Scott, look what I found. Check the link.

http://www.sjdiscounttools.com/thx312.html

I will check with the local Auto Parts stores to see if any of them have this tool. This looks like a handy thing to have. Bill
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Old 08-10-2006, 06:27 AM   #32
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Idle speed is 550 in drive, 700 in neutral, +- 25 rpm.
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Old 08-10-2006, 06:32 AM   #33
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Vacuum Plugs

I always used golf tees or sharp pencils.
Bright yellow pencils are easier to see when you are done.
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Old 08-10-2006, 06:39 AM   #34
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Fast Idle

Quote:
Originally Posted by overlander63
Idle speed is 550 in drive, 700 in neutral, +- 25 rpm.
Thanks Terry, that's good info. Now I know what to shoot for. Bill
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Old 08-10-2006, 09:07 AM   #35
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leb--you sure are dragging this thing out !!!! Maybe you just have more patience or more willing to drive a vehicle with problems then I am. I would have at least diagnoised this thing and probably had the throttle body off. You could have pulled it off, made a gasket from gasket material and been done in less time than you've spent on this thread!!!!!!!!!!----pieman
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Old 08-10-2006, 09:55 AM   #36
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Quote:
Originally Posted by Mike Lewis
leb--you sure are dragging this thing out !!!! Maybe you just have more patience or more willing to drive a vehicle with problems then I am. I would have at least diagnoised this thing and probably had the throttle body off. You could have pulled it off, made a gasket from gasket material and been done in less time than you've spent on this thread!!!!!!!!!!----pieman
pieman - Wow! Too bad you are not here......you would have this problem fixed, long ago!! Yes, I am a bit more patient than you, apparently. Why? Couple of reasons, 1) this is not a disabling problem that has to be fixed TODAY! 2) I have other things on my plate and have to focus on this problem in my spare time. And mostly because I'm not the EXPERT in this stuff and I do not want to create additional troubles by screwing something else up while trying to fix this problem. Have you ever done that?!! Just taking the throttle body off and replacing the gasket is not the objective here. The objective is to fix the fast idle problem. And, based on what I know right now, replacing the gasket would just be wasted effort and the problem would still exist. Bill
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Old 08-10-2006, 12:59 PM   #37
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Fast Idle

Scott, some feedback on your suggestions.

First, there is no "bean shaped" hole anywhere on my throttle body (it figures) that I can get at. As I mentioned earlier, I have a Haynes Manual and there are at least 3 different versions of the TBI pictured in the manual. In one top-view photo, I can see what looks like a bean shaped hole on the right rear, but it is a different version of TBI than mine. On mine, the injectors and their mounting device covers the complete back area of the throttle body. They are mounted on a plate that is elevated above the TB surface about 1/4 inch. If the bean shaped hole is there, it is under that mounting plate somewhere. So I wasn't able to do the WD40 test on that.

I unplugged the PCV valve and blocked the air intake and got a slight decrease in engine idle speed (not down to 500 RPMs). Then I removed the hose right at the TB, plugged it with a golf tee and got a drop in idle speed to 800 RPMs. The elbo hose connection was either split or I split it pulling it off. It was hard and brittle. I will be replacing two of those.

I removed and blocked all of the vacuum hose connections to the TB and intake manifold, one at a time, and nothing helped.

Now the mystery connection. Just below and to the right of where the PCV valve hose connects to the TB, is what appears to be a VACUUM connection on the TB with a recently replaced rubber hose that goes to a switch device with an electrical connection and another stiff plastic hose that goes from the same device over to the vapor cannistor. The mystery is when I removed the connection there was no suction from the TB side....none! I wondered if it was plugged up or was it supposed to be that way? Wondered if that could effect my idle speed in any way.

With the PCV valve vacuum connection plugged, I get idle speed of 800 RPMs, in neutral, a little less than 700 RPM in gear and about the same with the AC on. When I turn the AC on, the speed initally drops to about 600 RPM, then the computer increases it back up to 700.

I'm now thinking that I will just replace the TBI gasket anyway, since I have a new one. I suppose that it is possible that there is a leak on the underside of the gasket, between the gasket and the intake manifold, that I couldn't get to with the WD40 test. The gasket extends out from the TB as much as 1/2 in in several places, making it difficult to get to the underside with the WD40. Can you think of anything else? Bill
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Old 08-11-2006, 12:34 AM   #38
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1960 24' Tradewind
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Lebolewis ,
I would pull the TBI off and just do the gasket ,Im surprised there is not a bean hole somewhere .The idle air comes in thru the passage around the IAC
to the engine ,so it is someplace.Some vacuum ports do not have suction at
idle ,so don't worry about that .The pcv test would tell me that its fine.Yes pull it off ,do the gasket .You do not have to mess with the injectors ,except
to unplug them ,electrical connections .There are the 4 manifold to TBI
bolts ,follow the haynes manual ,and you will get it .Those thexton plugs
are good ,but you past that part now.I will wait to see how tha gasket
replacement goes and the results,before I send you more ideas ,a step
at a time .Pulling of the vacuum lines will not hurt anything ,don't worry
on that.The only other thought I will give ,is the coolant temperature
sensor ,two wire ,a yellow wire and a black wire connector small plug,
If it thinks the engine is cold all the time ,it will idle fast also ,but the IAC
pintle will be retracted some ,not closed .That would be my other thing to check .The temp gauge is separate and has no relation to the coolant sensor
for the computer.Your manual should give you some info on that under
emission controls and fuel systems .The air port is somewhere by the IAC
motor .Now on page 6-2 in my chevy truck haynes ,shows the coolant sensor
picture #6.Also on page 6-6 the ALDL connector can be used to flash the
check engine light for codes ,jump A and B key on engine off and the light will flash, it shows the procedure on the same page .Go with this for now and
see where your at.

Scott of scottanlily
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Old 08-11-2006, 06:38 AM   #39
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Idle Adj

Got a digital camera? Post pictures. Might clear up a lot, a lot quicker. Just a suggestion.
Beginner
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Old 08-11-2006, 08:31 AM   #40
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Quote:
Originally Posted by Beginner
Got a digital camera? Post pictures. Might clear up a lot, a lot quicker. Just a suggestion.
Beginner
Yes, that would explain a lot. I thought of that some time ago, however my digital is a real cheapo, actually free, with a fixed focus lens and it will not show detail closer than about 4 feet. Bill
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Old 08-11-2006, 12:48 PM   #41
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Fast Idle

Ok Scott, more work done......and the fast idle is still present!!!!!!

I replaced the TBI gasket this morning. It went pretty easy except for the removal of the grommet that feeds the injector wires down through the TB top and out. I couldn't figure how to get that thing out, it's not your ordinary grommet, it's odd shaped and it's special made. I didn't want to damage it.....probably cannot get a replacement easily. I finally got it out with minimal damage. The 2 air filter housing mounting rods do indeed screw into the top of 2 of the 3 TBI mounting bolts, on my version. I temporarily removed them so I was able to torque to spec all three TB mounting bolts. Reassembled everything and still have idle at 1000 RPMs in neutral and 800 RPMs in gear. I suspected as much when I examined the old TB gasket and found it to be in very good shape. But I did find the "Bean HOLE" you mentioned! (it's much bigger than a bean and more like a Trapezoid shape). And.....looking down in the bean hole, I noticed that the IAC was open in it's "at rest" position. With everything reassembled, and the engine running, I sprayed WD40 into the Bean Hole and the engine speeds up, momentarily. That tells me that the IAC is "open", even with the engine running at 1000 RPM idle!! Does that suggest a defective IAC?? .....or what??
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Old 08-11-2006, 06:17 PM   #42
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No, that's pretty much how it's supposed to work. The IAC will be open a small amount when the engine is idling, although it shold try to close until the idle drops. After all this, you MAY have a IAC that is stuck partly open. They are about $30 or so for a new one, if you want to diagnose the old one by installing a new one.
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