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Discussion Starter #1
Did I miss the obvious?:confused:
The throttles need to turn all the way round to their stops.

When pushing the accelerator pedal flat down, there is about 25% more rotation possible on the throttle linkages.
I adjusted most of the slack out of the accelerator cable, but no, still not getting full rotation.
Then I lowered the accelerator petal using the little adjuster bolt behind the petal.
Now when you floor it, the throttles open fully.:M5rev:

Quite keen to drive it and see how much difference it makes.

Am I on the wrong track here? Your thoughts appreciated:typing:
 

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The throttle cable is quite long & works hard on these machines..
it's under quite a lot of load.
Over time it will stretch, I've adjusted mine before and yes, it wasn't
making full throttle !

It was missing about 5% though and not 25% ! ! !


Regards,

Alan.
 

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The throttle linkages can always be pussed a little byeond their full opening. The only correct way to check is manually operate the throttle lever and push it against it's stop (basiclally a screw on the throttle body of cyl #5 and #6). You should hear a slight click from the throttle position switch (TPS), telling the motormanagement (DME) it should operate in full throttle mode (ignoring the O2-and MAF sensors and saturate the fuel injectors). If you don't hear this click, you must adjust the basic-throttle body sync which requires the calibration of the three TB's in idle and full throttle positions and adjust the throttle linkages to compensate for the errors.

If the TPS works, you must check the operation of the throttle bowden cable and adjust it if necessary.
 

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Discussion Starter #4
The throttle cable is quite long & works hard on these machines..
it's under quite a lot of load.
Over time it will stretch, I've adjusted mine before and yes, it wasn't
making full throttle !

It was missing about 5% though and not 25% ! ! !


Regards,

Alan.
I agree with you, Alan
Previously with other vehicles I've owned, there was a very small % of slack.
With this car , when I first drove it, I was not overly impressed with its power. I figured there must be something causing the loss that I could find, hence the reason I went ahead with the purchase. To be honest I reckoned it was the CATS. This car has probably been run on leaded fuel for at least 10 years of its life. I'm sure the cats are slightly blocked, thats my next port of call.

With the throttle properly adjusted, the car is significantly quicker. It now feels like an M5.:M5thumbs:

My 25% (okay, maybe 20%:cool2:) is a close representation of the incorrect adjustment.
 

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Discussion Starter #5
You should hear a slight click from the throttle position switch (TPS), telling the motormanagement (DME) it should operate in full throttle mode (ignoring the O2-and MAF sensors and saturate the fuel injectors). If you don't hear this click, you must adjust the basic-throttle body sync which requires the calibration of the three TB's in idle and full throttle positions and adjust the throttle linkages to compensate for the errors.
I hear a click from the TPS as I crack the throttles open.
Definitely nothing up at the WOT setting:confused:

The throttles look pretty far open, linkages at acute angles.
You sure on this one, Raymond?
 

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the throttle switch itself is adjustable as well. There is an adjustment procedure, measuring resistance from various pins at different throttle positions etc. I'll try to find a link.

Here we go, try this link: http://www.bmwtechinfo.com/repair/main/741en/index.htm
 

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Make sure you get it completely right, test with hot engine aswell

Its easy to set it too tight, you wouldn't be the first to snap a throttlecable.
 

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the throttle switch itself is adjustable as well. There is an adjustment procedure, measuring resistance from various pins at different throttle positions etc. I'll try to find a link.

Here we go, try this link: http://www.bmwtechinfo.com/repair/main/741en/index.htm
This only works for the last S38B36's and the S38B38's. All S38B36's before 1992 have a throttle position switch that contains two micro switches with which three states are detected

1: Idle (All throttle bodies are closed, the idle control valve determines engine speed)
2: Normal (DME can operate in so calles stoichiometric mode, using the MAF and O2 sensor signals)
3: Full throttle (DME ignores the MAF and O2 sensor signals)

Resistance can be measured, but for the S38B36 (bar the last batches) it should be zero Ohms (+1 Ohm) to compensate for the test-lead resistance. The TPS can be adjusted indeed, but this should only be done, after the throttle bodies have been synchronized.

I have an FAQ's article in preparation for this one, but this takes time.
 

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Discussion Starter #9
To give you guys an idea how far out of adjustment it was -

Pre adjustment:
the rotating bar that activates all the throttle linkages has a cam looking extention on the side that connects to the accelerator cable.
At WOT it was pointing directly down, the 6h00 clock position.

Post adjustment:
at WOT it now points to the 7h30 position
It
 

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the throttle switch itself is adjustable as well. There is an adjustment procedure, measuring resistance from various pins at different throttle positions etc. I'll try to find a link.

Here we go, try this link: http://www.bmwtechinfo.com/repair/main/741en/index.htm
This only works for the last S38B36's and the S38B38's. All S38B36's before 1992 have a throttle position switch that contains two micro switches with which three states are detected

1: Idle (All throttle bodies are closed, the idle control valve determines engine speed)
2: Normal (DME can operate in so calles stoichiometric mode, using the MAF and O2 sensor signals)
3: Full throttle (DME ignores the MAF and O2 sensor signals)

Resistance can be measured, but for the S38B36 (bar the last batches) it should be zero Ohms (+1 Ohm) to compensate for the test-lead resistance. The TPS can be adjusted indeed, but this should only be done, after the throttle bodies have been synchronized.

I have an FAQ's article in preparation for this one, but this takes time.
Bringing this back to see if there was any clarification. The bmw repair manual uses the 6 pin TPS most of us have that shows what pins should read out 0 ohms at idle/WOT.

My vehicle suffered a melted piston on cyl. #1 at 320k miles. I chocked it up to failed injectors until reading a bit about this. Most all of my combustion chambers showed cracks between valve seats due to strenuous heat cycling, and after completely rebuilding my engine and installing an AEM wideband, I'm still not happy with the AFRs coming through the exhaust.

At WOT the car dances between 13 and 17 on the gauge annoyingly back and forth. Sometimes it reads perfectly, but mostly it does this dance.

I also have a weird idle issue where the car will dance around the idle sometimes at 1k rpm and then going to 1300 and sometimes even 1700. Messed around with the TPS and it doesn't do it as much, but I am worried my car is never reaching the enrichment cycle at WOT.

Hopefully tonight I will grab a multimeter to make sure the car is 1. reaching wot on the sensor by pressing the linkage to full open and 2. reaching wot by depressing the accelerator fully open.
 

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At WOT the car dances between 13 and 17 on the gauge annoyingly back and forth. Sometimes it reads perfectly, but mostly it does this dance.

I also have a weird idle issue where the car will dance around the idle sometimes at 1k rpm and then going to 1300 and sometimes even 1700. Messed around with the TPS and it doesn't do it as much, but I am worried my car is never reaching the enrichment cycle at WOT.
Turn the air cond off next time it goes to a 1,700 rpm idle and see if the idle goes back to normal. If it does drop the rpm it's the TPS

GA25324 did this for a week and the problem was cured by a new TPS

Going back to the subject of the original post and checking the throttle butterfly this is one of the first things I do when I buy a used car.

A few years ago when I got my E34 M60B30 it was a slug and it was found that the TB wasn't opening past about 80% open, 10 mins work restored the performance of the little V8


.
 

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Turn the air cond off next time it goes to a 1,700 rpm idle and see if the idle goes back to normal. If it does drop the rpm it's the TPS

GA25324 did this for a week and the problem was cured by a new TPS

Going back to the subject of the original post and checking the throttle butterfly this is one of the first things I do when I buy a used car.

A few years ago when I got my E34 M60B30 it was a slug and it was found that the TB wasn't opening past about 80% open, 10 mins work restored the performance of the little V8


.

I just checked my linkages and it is opening 95%, but the tps is not working. Checked the pins and it is not ohm'ing out to zero at either idle or WOT

I wish they weren't $250 new :/


Sent from AutoGuide.com Free App
 

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This only works for the last S38B36's and the S38B38's. All S38B36's before 1992 have a throttle position switch that contains two micro switches with which three states are detected

1: Idle (All throttle bodies are closed, the idle control valve determines engine speed)
2: Normal (DME can operate in so calles stoichiometric mode, using the MAF and O2 sensor signals)
3: Full throttle (DME ignores the MAF and O2 sensor signals)

Resistance can be measured, but for the S38B36 (bar the last batches) it should be zero Ohms (+1 Ohm) to compensate for the test-lead resistance. The TPS can be adjusted indeed, but this should only be done, after the throttle bodies have been synchronized.

I have an FAQ's article in preparation for this one, but this takes time.


S38B36 TPS also has changing resistanse area, but Motronic 1.3 do not use it?
 
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