engine and drivetrain Tii Throttle Body Replacement

[OriginalOwner]

The obvious question not asked nor answered:  why change it ??  Perhaps whatever problem there is can be solved in a manner not requiring remove/replace of the throttle body.

 

Cheers,

 

Carl

Edited January 23, 2014 by OriginalOwner

[thehackmechanic]

Carl, ha! Beat you by 2 minutes!

[RED1602]

I took the car for smog test last year in July like I have been doing for years and she would pass by a little adjustment to the air or the fuel mixture. But last year no matter what it would not pass.

It idles only around 2000 RPM even after it worms up anything less than that and the car dies.

I drive the car and when I get to a light I have to manage the throttle so it won't die.

I blip the throttle idle goes up and then down and the car dies.

While running if you touch the eccentric cam thing in the tuna can the idle goes up and down and the car dies.

The Mechanic said that it seams that the shaft that opens and closes the throttle body butterfly is worn out and that is why it won't idle below the 2000 RPM. (car was hooked up to an analyzer the whole time) 

I found a good used TB on line so I thought I start  by replacing that. 

Edited January 23, 2014 by RED1602

[thehackmechanic]

As a previous poster said, if the bushing for the throttle body shaft is worn out, it can allow extra air to enter the engine, which will make it run lean, which could account for your symptoms. One way to check for vacuum leaks is to spray something like starting fluid or carb cleaner around the engine and see if the idle smooths out. This is more difficult in practice than it sounds, since a) I found that you have to extend the intake away from the engine with a big fat hose (I use a Porsche air duct which is exactly the right size) because otherwise, stuff sprayed around the engine finds its way in through the TB and you haven't actually found an intake leak, and the effect of finding an intake leak often isn't as dramatic on the RPM as you'd think. I do this with an exhaust gas analyzer, and, as I said, extending the intake to the TB. You can also try it by taking an 18" or so length of hose about the diameter of a garden hose, putting it to your ear, and moving it around to listen for intake leaks.

 

Search "tii intake leak" and you'll find common sources, including:

 

--Dipstick

 

--Intake gaskets 

 

--On a '74 you have metal plenums, they're tighter and less leak-prone than the early plastic ones 

 

--Cold start system / plunger not fulling extending, auxiliary air source not completely closing 

 

If you suspect your TB has a worn bushing that's letting air in, and you find a cheap TB on eBay with a good tight bushing, there's nothing wrong with changing it. But I'd recommend that you look at it in the context of one step in the process of chasing an intake leak.

 

I'd also recommend you start by adjusting the valves and verifying that the engine timing is correct. Timing will play havoc with the idle and correct running on these cars. On mine, the distributor wasn't even advancing.

 

 

Rob

[lilmo]

I would suggest working on the sync procedures before changing out the TB.  I've sync'd my tii enough to know that the symptoms you describe can result from chasing my tail, i.e., quarter turn of this screw, sixteenth turn of that screw, 2 degree turn of the dizzy.  Still not quite right?  Then another eight turn on the first screw . . . . .  Start with the baseline procedure from the manual.

[RED1602]

I'm listening and taking it all in guys, please keep them coming.

Thanks

 

KM

1970 1602 W/s14 (M2) 
1974 2002 Tii (Show) 
1989 325ix (Winter) 
1991 325ic (Summer)
2008 128i (Daily)

[JohnS]

Note that tiis came with two different types of throttle bodies (early and later style).  Both my '73 and '74 have the later style throttle body that supposed to be easier to adjust the mixture on.  I think that later style ones are the preferred ones, but either type will work on any tii.  Just an FYI...

[bnam]

I agree with lilmo.  The mechanic seems to have indicated that the worn throttle linkage shaft (not a worn throttle shaft/bushing - if I've read what you wrote correctly) is the cause.  If that was really the case, you can put the new throttle shaft into your old throttle body and solve that issue without disturbing the other (idle air mix) settings.  

 

But, that may not be the problem and you may want to see how much of the bad running can be eliminated on your current set up.

 

The manual is pretty straightforward and I did not have any issues synching the setup on my 74tii (as first time owner of a Tii or any  BMW).  I had a challenge trying to get my off-idle mix correct, but it helped to have an O2sensor setup.

 

B

[jgerock]

First thing I would check is the little spring under the round lid for the throttle body. If that is weak, the butterfly will not close properly (or will be slow in movement).

Your throttle body may not look like this one.

 

Here is an example of "pinning" the upper cam

 

I vote for not R&Ríng the throttle body just yet.  Let's see what is going on with your existing set-up.   Maybe the main throttle lever return spring (horizontal) is weak or broken>>>?

[OriginalOwner]

+1 lilmo on messing with that little screw thingie inside the tuna can ..... jgerock shows an excellent picture thereof.

 

on my '74tii that adjustment is finicky and often changes with the color of the sky, or which shoes I put on that morning.  I don't want to say that messing with it is an art form, but it's worth the effort to first mess with it awhile.  Make sure the engine is at operating temperature, then tweak it and drive around and see how it acts.

 

and +1 jgerock on the main throttle lever return spring, make sure it's giving you plenty of pullback force.

 

Cheers,

 

Carl

[RED1602]

Thanks everyone I'll try to check all that next weekend, And let you know the results.

Thanks again

KM

[Mike Self]

Mike McCartney's second 2002 restoration book has a very comprehensive section on setting/tuning tii fuel injection systems.  I've never owned a tii, but after reading the section I think I could perform the tasks to set the system up properly.  

 

If you don't have a copy of the book you should get one, or have someone on the board scan the appropriate pages for you.

 

cheers

mike

[RED1602]

I'll look for the book, thanks Mike!

Edited January 24, 2014 by RED1602

[OriginalOwner]

Downloads:  Video and Manual .... this just got posted in another thread:  http://www.2002tii.org/kb/59

 

Cheers,

 

Carl

Edited January 24, 2014 by OriginalOwner

[LarsAlpina]

Maybe some more questions:

 

Did the problem with the engine dying below 2000 rpm occur just overnight or from one day to the next? Or was that a process with things getting worse slowly bit by bit? Did you change any parts or turn any screws right before it occured? Do you use the car regularly or are there longer periods when it is standing still?

 

Regards, Lars.