Idle rises when car warms up...

[mikecp]

Note the different sensor on duggi's car though. As I suspected, someone put a TTS here on your car instead of the temp sender for the gauge.

Yeah just noticed that the sensor on mine is a thiccboi compared to Duggi's.

Thanks for providing the the vin for the 325. i'll get the correct sensor installed.

Edit - you mentioned adjusting the TPS sensor is a PITA. is there a link with the procedure that i can follow? or can i simply google M20 TPS Sensor adjustment

[duggi]

Note the different sensor on duggi's car though. As I suspected, someone put a TTS here on your car instead of the temp sender for the gauge.

Good catch! This is likely the issue...I wouldn't even bother touching the TPS until you get this swapped-out for the right sensor =)

As far as the engine configuration...on one hand you have a car with a lot more power than it would have had as stock (I'm assuming unless he did all that work and it's running the stock ECU), but on the other you're not going to get the same great gas mileage the 528e is capable of in stock form -- I used to get ~32 highway on average with my auto in it's original configuration. Now I can maybe get ~27 if I'm light on the gas with the manual installed, so there is that trade-off.

[mikecp]

If thats the sensor for the temperature indicator on my cluster and i have the incorrect one, do you think its likely causing my idle creep also?

Note the different sensor on duggi's car though. As I suspected, someone put a TTS here on your car instead of the temp sender for the gauge.

What does TTS mean?

[duggi]

If thats the sensor for the temperature indicator on my cluster and i have the incorrect one, do you think its likely causing my idle creep also?

Note the different sensor on duggi's car though. As I suspected, someone put a TTS here on your car instead of the temp sender for the gauge.

What does TTS mean?

It might be causing your idle creep. TTS = Thermo-Time Switch. It's a component of the early Motronic 1.0 idle control system and isn't used when upgrading to Motronic 1.1 or 1.3. You'll want to replace that with a proper temp sensor.

[mikecp]

If thats the sensor for the temperature indicator on my cluster and i have the incorrect one, do you think its likely causing my idle creep also?

Note the different sensor on duggi's car though. As I suspected, someone put a TTS here on your car instead of the temp sender for the gauge.

What does TTS mean?

It might be causing your idle creep. TTS = Thermo-Time Switch. It's a component of the early Motronic 1.0 idle control system and isn't used when upgrading to Motronic 1.1 or 1.3. You'll want to replace that with a proper temp sensor.

Got it - i just ordered the right switch.

once it arrives i'll throw it in and i'll follow up!

[ahab]

To check the TPS, first open the throttle by hand with the engine off and listen closely for a click underneath the throttle body in the area where the green arrow points. If you hear no click then you're pretty sure to have a misadjusted TPS. Even if you do hear the click however you still need to test it. It's directly connected to the shaft that the red arrow points to, underneath the throttle body. You can disconnect the TPS and simply put a meter on the pins to see when they open and close but this is complicated due to access and requires 4 or 5 hands. A pigtail as shown below will help with testing but for adjustment the throttle body really needs to come off. So, the easiest way to attack this whole affair (believe it or not) is to remove the throttle body from the car at the get go. Intake bellows comes off, throttle and cruise cables, various vacuum hoses. It's a bit intense, but it's not complicated in the sense of hidden screws and whatnot (with the exception of the TPS itself).

The test process is easiest with that pigtail if you have access to one but it's not mandatory if you have a steady hand. The TPS has three pins. One pair of pins will have continuity at rest and open when the click occurs, the other pair will be open and close at about 80% throttle. You need to loosen the two phillips screws that hold the TPS in place and rotate it on the shaft so that you can hear it clicking and see the meter open. You need to lock it back into place so that AS SOON as the throttle plate moves the meter shows an open circuit, the click is usually very close to this occurrence for the obvious reasons, but not always. There is no adjustment for the other switch in the TPS, if the other two pins don't close at WOT (or close) then the TPS should be replaced. Given the complexity of all this, you should test the CTS (the new blue sensor) first to make sure it's doing its job, as this will have a big effect on idle speed. Due to the way your idle only rises when warm I tend to think this is a mixture problem as opposed to a faulty ICV, but you should test that as well. The Bentley has the specs, I don't remember them.

[ahab]

When you get your new temp switch, change it out on a completely cold engine and be prepared to do a quick swap in order to minimize the coolant loss. Ground that wire first too though so you know that your gauge and circuit are functioning.

[demetk]

Sounds like your TPS may be out of adjustment. PITA on an M20, but that would cause this exact problem. Do you know how to check?

I agree on this. TPS may have a heat related issue. It may be fine cold and be sending an idle signal but may be faulty when hot and not sending an idle signal. You can always test that idle signal wire directly at the ECU.

[mikecp]

Sounds like your TPS may be out of adjustment. PITA on an M20, but that would cause this exact problem. Do you know how to check?

I agree on this. TPS may have a heat related issue. It may be fine cold and be sending an idle signal but may be faulty when hot and not sending an idle signal. You can always test that idle signal wire directly at the ECU.

Ill first swap out that first brown sensor thats incorrect and see if that fixess the idle issue. The TPS adjustment looks like an absolute PITA.


As for trying to figure out just exactly what i have going on under the hood, i know now that I have the motronic 1.3 and also maybe a 325i intake manifold ? is the head from a 325i? im not familiar with the "e2i" swap at all. so im just trying to get my ducks in a row and figure out what i have going on down here.

[ahab]

Unfortunately the brown connector is only connected to the gauge and will not influence mixture. A simple way to tell would be to unplug it when you have a high idle (and low for that matter) and see if there's any effect at all. Once the engine is hot you should also do that with the black connector next to it, which tells the ECU the coolant temp. If you get no change in idle then that could be a clue that the sensor is out of spec. Ideally you want to put a meter on it though for a conclusive reading. You can certainly wait until you get the new sensor to see if you gauge works but if I were you, I'd try that wire test first. If the needle doesn't peg a new sensor won't do anything.

[mikecp]

Unfortunately the brown connector is only connected to the gauge and will not influence mixture. A simple way to tell would be to unplug it when you have a high idle (and low for that matter) and see if there's any effect at all. Once the engine is hot you should also do that with the black connector next to it, which tells the ECU the coolant temp. If you get no change in idle then that could be a clue that the sensor is out of spec. Ideally you want to put a meter on it though for a conclusive reading. You can certainly wait until you get the new sensor to see if you gauge works but if I were you, I'd try that wire test first. If the needle doesn't peg a new sensor won't do anything.

hahaha i figured it wouldve been wishful thinking to swap the brown one and *poof* my idle is fixed.

i'll try measuring the ohms for the black connector (i'm assuming youre talking about the one that you circled earlier right?) and get back to you guys.


thanks for all the help!

[ahab]

i'll try measuring the ohms for the black connector (i'm assuming youre talking about the one that you circled earlier right?) and get back to you guys.
!

Yes but make sure you do it on a hot engine, and measure the sensor, not the connector.

[mikecp]

i'll try measuring the ohms for the black connector (i'm assuming youre talking about the one that you circled earlier right?) and get back to you guys.
!

Yes but make sure you do it on a hot engine, and measure the sensor, not the connector.

The sensor being the brass part thats visible ?

[ahab]

Yes, when the connector comes off you will see two metal prongs on the sensor. Set your meter to 2k ohms and touch each prong with the probes. A hot sensor should read somewhere around 300 ohms. For reference, a cold sensor should read much higher, ~25k ohms (if you want to check this too, set your meter to 200k ohms). In this condition the ECU interprets the high resistance as a cold engine and it lengthens the injector pulses which adds more fuel to aid in combustion at startup. If your car is coming up to temp but this sensor is bad, the ECU may not be cutting back the extra fuel and the result would be a high idle.

[mikecp]

Yes, when the connector comes off you will see two metal prongs on the sensor. Set your meter to 2k ohms and touch each prong with the probes. A hot sensor should read somewhere around 300 ohms. For reference, a cold sensor should read much higher, ~25k ohms (if you want to check this too, set your meter to 200k ohms). In this condition the ECU interprets the high resistance as a cold engine and it lengthens the injector pulses which adds more fuel to aid in combustion at startup. If your car is coming up to temp but this sensor is bad, the ECU may not be cutting back the extra fuel and the result would be a high idle.

Hey ahab,

So update. I got the proper switch installed yesterday (the brown one) and i got my temp gauge back. But it did not fix the idle issue as I hoped but in reality I didn't expect it too.

I also took some readings of the blue sensor while the engine was hot and what I found was that the sensor would read 450 then bounce at 300, 200 and ultimately come to 80 or 90 (btw, i hope im reading it right. this is with my meter set at 2000 and the numbers that pop up are "400", then "320", then "8" and then "9") . and it would do the same thing over and over, 450 - 300 - 200 - 8 - 9.

Am I looking for a consistent 300-ish that does not fluctuate?

[ahab]

You may have just identified the problem! It should be a steady reading. Assuming the car is warm. It would not be the first time I saw a brand new sensor, and yours looks to be, be faulty. Go to FCPeuro or your favorite parts house and get the correct Bosch sensor. It should be light blue, not dark blue or black.

[mikecp]

You may have just identified the problem! It should be a steady reading. Assuming the car is warm. It would not be the first time I saw a brand new sensor, and yours looks to be, be faulty. Go to FCPeuro or your favorite parts house and get the correct Bosch sensor. It should be light blue, not dark blue or black.

Lets hope so! I'm gonna place the order now.

But help me on something that im trying to grasp. with the multimeter set to 2000 my reading shows 003 and 002. That is 2-3 ohms resistance? Im taking my reading and muplitplying it by 1000.

.003 x 1000 = 3 ohms

Am i right?

[ahab]

When you set the meter to 2000, you are setting the high mark given the limited decimal places on the display. Because you want to measure 300 Ohms, by setting the ceiling to 2,000 you are ensuring that 300 will show up as 300. Since your meter isn’t going to show 4 places of resolution, if you were to set the ceiling at 20,000, the 300 would show up as 030 because you’ve moved the decimal point. Confusing I know, I hope this explanation makes sense. Bottom line, if you set the meter to 2,000, then 300 (or 264 or 511, or whatever the 3 digit value actually is) would show up in the display. If you wanted to measure 30 ohms you would set it to 200, and if you wanted to measure 3 ohms you would set it to 20.

[demetk]

Why do you need to complicate your lives? Get an auto-ranging meter for like $20.

[mikecp]

Got thew new sensor in. Everything is ALMOST fixed.

RPM's are steady at 1k now. Not the desired 750 i was hoping for. But, the RPM's no longer start at 750, climb to 1500, and stay there so the new sensor did do something right!

Now, the car starts at 1k and stays steady through out.

My TPS could be needing adjustment still?

I agree on this. TPS may have a heat related issue. It may be fine cold and be sending an idle signal but may be faulty when hot and not sending an idle signal. You can always test that idle signal wire directly at the ECU

I think this may be the issue. Can you explain the idle signal wire at the ecu? I'm not sure where i can find that wire or how to test it.

[ahab]

Do you have a copy of the ETM? It just occurred to me that you can disconnect the ECU connector to test the TPS there, and maybe avoid all the pain of removing it just to test. Ideally you'd want two people but I suppose you could use the accelerator pedal to open the TPS. If you need the ETM, search for posts by user "a", he has a link in his signature. Then look up the pinouts for the TPS in the Injection Electronics section and test the pins at the ECU connector instead. If it passes the test you can rule that out. Congrats, you're getting closer. You should also check for vacuum leaks, those are a great source of high idle problems.

[Mike W.]

Got thew new sensor in. Everything is ALMOST fixed.

RPM are steady at 1k now. Not the desired 750 i was hoping for. But, the RPM no longer start at 750, climb to 1500, and stay there so the new sensor did do something right!

Now, the car starts at 1k and stays steady through out.

My TPS could be needing adjustment still?

I don't think so. My experience on M30s is that it's just a simple switch that tells the ECU to return to idle speed, can affect idle quality and dying when coming to a stop particularly with the A/C on, but doesn't affect idle speed. It's a simple make at idle, break just off idle, then make on a different contact on WOT, but does nothing in between. The idle side will also cut fuel off above about 1300 RPM. But testing is simple enough too.

What does it feel like, engine speed wise? On my 535 it showed about 650-700 at idle, but when doing smog tests it was always a bit over 800. Also if they tried to do a 2500RPM test using the tach it would fail because they weren't within the allowable range of engine speeds.

I agree on this. TPS may have a heat related issue. It may be fine cold and be sending an idle signal but may be faulty when hot and not sending an idle signal. You can always test that idle signal wire directly at the ECU

I think this may be the issue. Can you explain the idle signal wire at the ecu? I'm not sure where i can find that wire or how to test it.

[mikecp]

I don't think so. My experience on M30s is that it's just a simple switch that tells the ECU to return to idle speed, can affect idle quality and dying when coming to a stop particularly with the A/C on, but doesn't affect idle speed. It's a simple make at idle, break just off idle, then make on a different contact on WOT, but does nothing in between. The idle side will also cut fuel off above about 1300 RPM. But testing is simple enough too.

What does it feel like, engine speed wise? On my 535 it showed about 650-700 at idle, but when doing smog tests it was always a bit over 800. Also if they tried to do a 2500RPM test using the tach it would fail because they weren't within the allowable range of engine speeds.

My car has the M20. Does what you're saying apply to M20's as well ?

And as far as feel, ever since i put the new sensor in, the car pulls a lot smoother. It pulls all the way to 4-5k rpm no problem and comes back down without stumbling (not that it did that before). My only issue is that now, itll rest at 1000 RPM's. Dead even. Smoothly.

Do you have a copy of the ETM? It just occurred to me that you can disconnect the ECU connector to test the TPS there, and maybe avoid all the pain of removing it just to test. Ideally you'd want two people but I suppose you could use the accelerator pedal to open the TPS. If you need the ETM, search for posts by user "a", he has a link in his signature. Then look up the pinouts for the TPS in the Injection Electronics section and test the pins at the ECU connector instead. If it passes the test you can rule that out. Congrats, you're getting closer. You should also check for vacuum leaks, those are a great source of high idle problems.

I dont have the copy of the ETM. I'll search that user up to see what information I can gather. As for "testing the pins at the ECU", can you tell me what i'm testing for? Continuity?

[ahab]

Yes, go back to my previous description for TPS testing to see which pins are which. At the actual TPS, the center is the common and the two outer are the switches. It's only 3 pins so there are only 3 combos, eventually you'll get it. One set shows continuity until you touch the pedal, the other set shows continuity at about 80% throttle. Set your meter to 20 this time. I agree with Mike that TPS is unlikely to be causing a high idle but it's possible. The more common side effect is an idle that drifts down slowly. Who knows what someone else may have done to combat the high idle however so start there and you'll have to work through each component one at a time.

[ahab]

OK, you should do yourself a favor and definitely go get the ETM, but in the interest of fixing the idle here's the pertinent info. Take the connector off the ECU and identify pins 2 and 3. You may have to take the ECU down to see the numbers, or you can just use process of elimination on each corner of the connector. Put you meter on pin 2 and a ground somewhere and you should get continuity. When you press the accelerator the switch should open. If that doesn't happen try a different "pin 2" in the connector. If you've tried all four and you don't get ground then your switch is almost guaranteed to be bad, or at least out of adjustment. Move the meter to pin 3 and ground and it should be open until the pedal gets close to touching the floor, then you should get continuity.

[Mike W.]

I don't think so. My experience on M30s is that it's just a simple switch that tells the ECU to return to idle speed, can affect idle quality and dying when coming to a stop particularly with the A/C on, but doesn't affect idle speed. It's a simple make at idle, break just off idle, then make on a different contact on WOT, but does nothing in between. The idle side will also cut fuel off above about 1300 RPM. But testing is simple enough too.

What does it feel like, engine speed wise? On my 535 it showed about 650-700 at idle, but when doing smog tests it was always a bit over 800. Also if they tried to do a 2500RPM test using the tach it would fail because they weren't within the allowable range of engine speeds.

My car has the M20. Does what you're saying apply to M20's as well ?

I think so, but I'm not positive, which is why I referenced it being a M30 I had experience with.

[mikecp]

Update.

So i took into consideration what you said, Mike W. and before i starting poking things on the ECU as per ahab's advice (which was sound btw) I started thinking maybe it was something simpler.

I did some googling and i came across a Revlimited forum thread about making sure the Throttle cable is secured properly and tight.

So I thought why not. I looked under my hood and my throttle cable had a ton of slack in it. I tightened it down, left just a little bit of slack, and that seemed to do the trick. I idle smoothly at around 800 RPM. Still a TAD bit high but im happy with it.

So tell me, can you guys explain why removing slack from the throttle cable helped? Is this just snake oil and i got lucky? Or did i actually do something to help...

lol

[demetk]

You got lucky. Probably got the TPS to click into idle mode because if it's not in idle mode it will idle higher.

[duggi]

You got lucky. Probably got the TPS to click into idle mode because if it's not in idle mode it will idle higher.

This is most likely correct.

[mikecp]

You got lucky. Probably got the TPS to click into idle mode because if it's not in idle mode it will idle higher.

I got it to "click" into Idle mode?

Could you explain that a little further? As Mike W. put it, i thought the TPS was just to detect whether there was input from the accelerator and to return the engine to idle speed.

So i somehow made the TPS switch into that mode? lolol