Hello everyone, I need technical information on a subject. In my 1991190E vehicle, 13 volts are constantly coming from the idle control valve. Can anyone help?
And when I insert the multimeter probes to measure pins 1 and 2 of the lmm pot, I cannot get voltage. I use Google translate. I apologize in advance for the article.

 

 

We need more info on this.

Please verify:

(1) When you disconnect the IACV at the connector you read 13V volts at the harness. (I believe this maybe normal as you have taken out the load and the controller may rail to full voltage but I am not sure of the behavior. Tell us what the rpm is with the IACV disconnected.

(2) When you plug it back in you read 0 volts at pins 2 to 1? That is not normal and it should be a PWM signal that averages 4-5 Volts

Perhaps state your problem when it is plugged in. Is it high uncontrolled idle of ~1000-1200RPM or something else.

You may be chasing ghosts.

 

Hello, I am grateful that you are trying to help me. Regardless of whether it is cold or hot, the ICV constantly gives 13 volts and there is constant movement between 1100-1500 rpm. When I remove the socket, the idle speed becomes 900 rpm. Could this be an OVP problem? I can read ohms on the potentiometer pins, but it does not give voltage, only when I give gas, the values ​​change, while the voltage is constant, it is impossible, it is very complicated and tiring. Greetings from Turkey.

 

Reis, I can help you even in Turkish if needed (hopefully not necessary) but you will need to answer my questions directly and not indirectly. This is the only way diagnosis from 15,000Km's away will work.

So see if you can do that with the questions on post #3 above. Line item by line item. Question first, followed by the answer.

And no your OVP is working, there is evidence of that.

So far, you have unplugged the IACV socket and the idle goes to 900 rpm and steady. This is a bit low but could be normal depending on operating temperature.

Most likely you have an IACV that needs cleaning or changed because it is intermittent and causing oscillations of the rpm. I have seen this in the past.

At this point you need some baseline measurements.

(1) Make sure your potentiometer is OK. Without unplugging it, measure the pin1 to pin2 voltage and report on it. I do not expect a problem there but I would like to know what it is.
(2) Make sure your microswitch works, by measuring the contact resistance with throttle closed and open.

After the responses there I think we can converge on this quickly.

Hadi Kolay Gelsin,

 

Corroded and or dirty wiring connections are capable of causing the issues you are currently experiencing as Dolucasi has also noted. I would first try making sure that all of the wiring connections are nice and clean and not corroded or dirty in any way. I would do this first. Continued testing with corroded or dirty wiring connections will continue to give you faulty data. This is an easy and inexpensive fix. Once you've done this cleaning, see how your car behaves. If there's still an issue now you've got a more solid base to work from and you're likely to get better data because of it.

 

[QUOTE=dolucasi;9074646]Reis, gerekirse sana Türkçe bile yardımcı olabilirim (umarım gerekmez) ancak sorularımı doğrudan ve dolaylı olarak değil yanıtlaman gerekecek. 15.000 km öteden teşhis koymanın tek yolu budur.

Yukarıdaki 3 numaralı gönderideki sorularla bunu yapıp yapamayacağına bak. Satır satır. Önce soru, ardından cevap.

Ve hayır, OVP'niz çalışıyor, bunun kanıtı var.

Şimdiye kadar, IACV soketini çıkardın ve rölanti 900 rpm'ye çıkıyor ve sabitleniyor. Bu biraz düşük ancak çalışma sıcaklığına bağlı olarak normal olabilir.

Büyük olasılıkla, aralıklı olduğu ve rpm'de salınımlara neden olduğu için temizlenmesi veya değiştirilmesi gereken bir IACV'niz var. Bunu geçmişte gördüm.

Bu noktada bazı temel ölçümlere ihtiyacın var.

(1) Potansiyometrenin iyi olduğundan emin ol. Fişini çekmeden, pin1 ile pin2 arasındaki voltajı ölç ve raporla. Orada bir sorun beklemiyorum ama bunun ne olduğunu bilmek istiyorum.
(2) Gaz kelebeği kapalı ve açıkken temas direncini ölçerek mikro anahtarınızın çalıştığından emin olun.

Oradaki yanıtları aldıktan sonra bunun üzerinde hızla birleşebileceğimizi düşünüyorum.

Hadi Kolay Gelsin,[/QUOTE
]Hello my dear friend, sorry for the late reply. The weather is very cold and I do not have a garage. I did what you said and the results are as follows: When the idle control valve plugs are plugged in, I get 5.5 volts. I think this is normal. I have a new potentiometer made in China. The voltage value is 0.7 volts. It doesn't matter whether the idle is cold or hot. It is always 1200 rpm. Sometimes when the car warms up, it suddenly becomes 500 rpm. My micro switch seems to be intact. . What is your opinion?

 

[QUOTE=190Efan;9075154]Corroded and or dirty wiring connections are capable of causing the issues you are currently experiencing as Dolucasi has also noted. I would first try making sure that all of the wiring connections are nice and clean and not corroded or dirty in any way. I would do this first. Continued testing with corroded or dirty wiring connections will continue to give you faulty data. This is an easy and inexpensive fix. Once you've done this cleaning, see how your car behaves. If there's still an issue now you've got a more solid base to work from and you're likely to get better data because of it.

Hello, I will take into account your suggestions and implement them, thank you for your answer.

 

Wow. These Large Language Model based AI translators are super! That is an excellent translation. Living in Silicon Valley, I do appreciate the advances there in the last few years.

Back to your issue Reis. Because your car is parked outside, there is always a chance of corrosion of your contacts under the hood being an issue for such an old car.
I have 2 and the one that is garaged does not suffer from corrosion at all, the other has these issues that I have to address occasionally. So 190EFan is spot on.

Now I would strongly advice against the Chinese aftermarket AFM pots. They will not last, but you may not have much choice in Turkiye.
Remember once the car warms up the AFM pot does not contribute at all to the the air fuel mixture, but it can send wrong signals and cause issues.

All this being said 0.7V at idle is perfect. So it is working and your ECU is also sending and receiving the correct signals. And your OVP is fine.

Please ignore what happens when you unplug the IACV. It rails to full voltage, that is normal.

When plugged in it is being controlled and it is forcing 1200 rpm. So the idle controller is for some reason forcing this. Now we have to find out why?

Now tell us:

Is this a 2.3L or a 2.6L engine or is it even smaller engine?
How many Km on the Engine?
Where are you in Turkiye?
Is it easy to start the car in the cold? What is the outside temp when you are starting the car?

I will ask you to unplug the coolant temp sensor and measure the resistance next.
If it is 4 connector one I will need:

Connector configuration below:
1 2
3 4

1 to 4 resistance
2 to 3 resistance.
I will need the coolant temp when you measure this.

Happy Motoring!

 

To be honest, I didn't expect this performance from the translation. It would be great if AI could offer repair solutions for old cars I will check the contact points, this will be the first thing I will do, unfortunately I do not have many options for the potentiometer. I will try to replace the potentiometer board I bought from China with the original potentiometer board, I agree with you, potentiometer does not inspire confidence.Engine 102.962 2.0L, Km 500.000 but apart from the jetronics it is still great, I live in the city of Erzurum in the east of Turkey and the weather has been between -15C° and -25C° for the last week, it starts without difficulty on the first try in the morning. The city's elevation above sea level is approximately 6000ft. In fact, if you look at it, even this affects the operation of my vehicle. My water temperature sensor has 4 pins. I took measurements today and I see 80C° 200 Ohm resistance on pins 1-2, 3-4.Greetings from eastern Türkiye.

 

Do not change the AFM potentiometer now Reis. You can unplug it and perform the AFM sweep and measure the resistance throughout the sweep range and see if it increases from 1.X ohms to 7-8K ohm without jumps in resistance but I'm sure it is new and it is OK. This is not your problem anyway.

Your coolant temp sensor appears to be fine as well. So the problem is not the sensor but when the weather is a bit warmer to work on the car you should measure the same resistance on the ECU connector. There could be a discontinuity between the sensor and the ECU. How clean is your ECU connector? Is it corroded at all? Make sure you disconnect the battery when you unplug the ECU connector. It would not hurt to clean that connector with a electrical contact cleaner. Always touch the ECU body with one hand when you touch the contacts so there is no static buildup.

But before that, have you measured your Duty cycle lately? What is the duty cycle at, when running cold and after it warms up?

It is great that your car starts easily in -20C weather, that means the ECU is working, cold start valve must be working as well.

It is entirely possible that your idle controller is malfunctioning as well.

While you are at it, please also measure the resistance of the intake air temp sensor. At Erzurum temps in winter that should be very high (like 3K-5Kohm)

 

Tekrar merhaba sevgili arkadaşım, umarım iyisindir, Uzun bir aradan sonra söylediklerini kontrol etme fırsatım oldu; O2 sensörüm bozuk, değiştirmem gerekiyor, emme havası sıcaklık sensörü çalışıyor, veriler uyumlu, ECU bağlantılarını kontrol ettim ve herhangi bir bağlantı kopukluğu bulamadım, ancak bir duman testi denedim ve benzin dağıtıcısının altında bir hava kaçağı olduğunu buldum. Motor devri yaklaşık 20 gündür dalgalanıyor ve bazen 2000 rpm'de sabitleniyor ve kendiliğinden artışlar oluyor,

aracımın rölanti kontrol valfine doğrudan 12 volt verdiğimde açılıp kapanıyor, ancak fişe taktığımda hiçbir hareket yok ve fişe elektrik geliyor, yorumunuz nedir?
Selamlar .

 

Hi Reis,
To capture what you are saying:
(1) You have established that your O2 sensor is not working.
DOLUCASI>> You need to replace your 02 sensor first if it is truly not working. How did you establish that it is not?
(2) Your air intake sensor is working and within spec
DOLUCASI>> Great, one less thing to worry about
(3) You checked your ECU connections and everything is in tact.
DOLUCASI>> Good
(4) You failed a smoke test as there is a leak coming from under the Fuel distributor (this is most likely your AFM rubber Boot that is cracked)
DOLUCASI>> Depending how bad the vacuum leak is this could be a problem. You should either replace it or just patch it to keep diagnosing. This will cause unstable and rough idle but not cause the 2000rpm
(5) Your rpm's have been high fluctuating and sometimes landing at 2000rpm
DOLUCASI>> This is generally because of a bad/dirty idle control valve, you will need to clean it with a carburetor cleaner or acetone, but you may have to replace it. I have seen that with a dirty Idle control valve the ECU will try to control rpm's, it can not and it will start violently fluctuating and sometimes settle at 2000rpm.
(6) If you test the idle control valve, by supplying it with 12V it opens but when you plug is back in, even though there is a signal at the connector when you plug in you are getting 0 volts.
DOLUCASI>> Please measure the resistance of the idle control valve. I believe it is supposed to be either 8ohms or 20ohms, I do not remember the spec. Let's see what ours is. Also, after you unplug it you said the idle fluctuations disappear and it idles at ~900rpm. Tell us what happens when you plug it back in as the car is idling. Does the engine stall?

Let us know what the resistance of your idle control valve is please.

 

Hello again after a long time, I could not detect any voltage fluctuation in the O2 sensor measurement. I think it should be changed. The last change was probably 200k km ago and the O2 sensor is not taken seriously in Turkey for these vehicles.
As for the idle valve, I cleaned the valve, I read 6 Ohm resistance in my measurements, and the vehicle stalls when I plug it in. Also, as I mentioned before, I bought the Afm pot from China and installed it. When I compare it with the old original, I measure 2.80 Kohm resistance on pins 1 and 3 in the Chinese one and 4.0 Kohm in the original one. What kind of an answer should I expect from this?
And what's more, the car was working once before, now it is having a hard time and it won't choke. Do you think the best solution is to pour a can of gasoline and burn the car? Regards..

 

Welcome back Reıs! Unfortunately for these cars the O2 sensor is not optional, you will need a working O2 sensor. Yes 200k km is a long time ago. They usually can go up to 150k km if you have a clean running engine with no oil burning. If it burns oil they get covered in soot sooner. And your emissions can not operate without an working 02 sensor by design.

6 ohms is a little low for the idle control valve. The specification I believe is 8 ohms but if it is working that is ok. It seems it is because when you unplug it, I assume the rpm goes up and when you hot plug it back in the engine stalls because the idle controller is not fast enough to recover. All normal.

On your AFM pot, it is NOT normal to have a 2.8Kohm between pins 3 and 1. I am used to seeing 4+ Kohms, more like 4.2Kohms. Your control unit supplies 5V to pins 3 to 1. That is the reference voltage.
Any chance you can measure the voltage after you plug it in? Are you getting that 5V? If not, that will be a problem potentially.

When you say "the engine is having a hard time and it won't choke" do you mean when cold it is a hard time raising the idle to 1000rpm or more until the engine warms up a little? Do you mean "choke" like an old fashioned carburetor engine?
This could be related to the AFM pot issues.
Remember the AFM pot's most important role is the following:
(1) During cold running it directs the ECU to enrich the mixture momentarily only when you press the gas pedal so the engine does not struggle
(2) During cold running it inhibits the fuel cut-off. Either his is intentional or a side effect but this is what happens because:
(3) After the car warms up the ECU uses the AFM pot pin 2 to pin 1 value as a third indicator of whether the engine is in idle or not. The other 2 are of course the microswitch and the Throttle plate sensor. So the AFM pot may just be another 3rd redundant indicator. This is why if unexpected pin 2 to pin 1 value is presented to the ECU during idle (microswitch and throttle plate both indicating idle) the IACV will start misbehaving and may go into high idle or worse start oscillating.
(4) So at operating temp it does virtually nothing but act as a third indicator for switching from running to idle for your idle controller.
(5) It may have another benign function near full throttle but it must be non critical at least for me as I never full throttle my cars and I'm not on a racetrack ever. The ECU just maybe looking for 2 inputs for full throttle, TPS and AFM pot combination, but I do not know this for a fact.

So at this point it is wise to measure both pin 3-1 voltage and pin 2-1 voltage AFTER the car warms up and report on what you get from this Chinese out of spec AFM pot.
You may want to repeat these measurements with your original AFM Pot.

By the way since you replaced the AFM pot, did you adjust it properly? Do you know how?

Too soon to burn down the car just yet Reis.

 

I haven't been able to make measurements for the AFM potentiometer yet, I will write as soon as I do it. When the engine is cold, it does not run at 1000rpm. As soon as it starts, it starts at 1500rpm and does not drop yet, it rises but does not drop. The steps I follow while adjusting the AFM pot are as follows: I install the new pot, start the car and wait for it to reach operating temperature (80c°), make sure that all electrical parts are off while the car is running, and set the potentiometer to 0.70 volts. Is there a mistake in these steps? Best regards

 

Hi Reis, unfortunately you can not adjust the AFM pot unless you can make the car idle correctly. The POT adjustement is exactly that, making sure that the AFM plate is deflated "approximately" correctly during proper idle. This is why it is adjusted when engine is at operating temp.

I would first take the air filter assembly off and when the engine is not running and inspect both the AFM plate and the throttle plate for "binding" (tutuklanma).
Make sure the throttle actuators are not binding, and if you have cruise control disconnect that connector if you can at this point.

The chinese AFM pot could also be a culprit here. If you have the old AFM pot, you should put that back in at least it has the correct pin1 - pin3 resistance of 4.x ohms, and with the engine off AND the AFM pot resting in its closed position adjust it to 1.5Kohm (pin 1 to pin2) as a starting point.

Also check the other 2 sensors that determine idle. Microswitch and Throttle plate switch should be checked for operation. The microswith should be properly contacting/open and similarly with throttle plate switch (pin 1-2 on TPS should be shorted when throttle is closed)

One thing you said bothers me. You said you disconnected all electronics while adjusting AFM potentiometer. You should not do that. All sensors should be connected at all times otherwise the ECU will behave unexpectedly, probably by design.

Also AFM pot adjustment is very sensitive, all you should need it to loosen the screws just one quarter turn each and "tap" it with a screwdriver ever so lightly. If you are having to turn it by hand we know there is something seriously wrong.

 

By electrical components, I mean the radio, interior lighting lamps, etc. I am not tampering with any parts in the engine compartment, so the method I used is wrong, I will follow the path you mentioned and I will write to you again, thank you.

 

Ok Reis, I misunderstood. Yes turning off electricity consuming equipment is fine.

I have never seen a high idle like yours. It gets stuck after you press the gas pedal and never goes back to idle. It could be the TPS, if it is adjusted way off it tends to cause high idle that oscillates/cycles.
Yours gets stuck. It almost feels like a mechanical sticking issue, but first re-adjust AFM pot (if you can). It can only be adjusted at ~750rpm and in idle.

 

Hello again, Dolucasi, I did the work as you said, I bought an original potentiometer from a different car and tried it, although I tried 4 different potentiometers in total, there is no change in the speed as I told you, even when adjusting the potentiometer, there is no change in the speed. While doing these, we tried it with an engineer who used to work for Mercedes and checked all the throttle and micro switches, there is no problem, the complete set is from a donor car whose potentiometer has not been tampered with. He offered to install the flowmeter and try it and we are thinking of doing it that way, what do you think? While all this is happening, when I unplug the idle valve at operating temperature, everything returns to normal. This may be normal, but the only thing that caught my attention is, wouldn't it remain stuck if there was a mechanical jam? And as I mentioned in the previous topic, it barely works 5-6 times with long cranking when it is cold. Could it be the fuel pump relay that is to blame?

 

Hi Reis, good to know there you do not have a mechanical issue and all idle control switches are fine. Your symptoms surely are not common and I am suspecting something is seriously wrong with your ECU and/or MAS unit. I do not know if they are behaving correctly at all. These units are very reliable however in extreme weather conditions for many years if the car has been sitting outside bad things happen to electronics after so many years. If you have spares of these you can try swapping them in to your car. SInce you could do this with an AFM potentiometer, I'm hoping you can do this with these units as well.

If you do not, then the best thing to do is to monitor your EHA current. Does it behave normally?
(1) Ignition on, Engine off : +20mA
(2) Engine being cranked : approximately +64mA (also monitor your cold start valve voltage when you crank. CSV should go to 12V as you crank the engine while it is plugged in for 2 seconds)
(3) Engine running cold right after you start it: +60 to +140 mA (below 0c, depends on temperature) to +20mA (approximately 20c)
(4) Engine running at operating temperature +3mA to -3mA (if AFM lever is adjusted correctly) at idle and within +/-4mA if the engine rpm is raised to 2500rpm.

You can also tell us what happens to the EHA current when you unplug the IACV while the car is idlling

You will need to make a break out harness for the EHA current. Or use alligator clips temporarily by disconnecting the plug. You need to insert the current meter in line with one of the leads.
When you do this current meter insertion make sure your battery is disconnected, and you should always ground yourself to the chassis to avoid damaging your ECU.

So more diagnostic work is ahead of you I am afraid, if you do not have the ability to swap in a different and known good ECU and MAS unit.

(A) Also, do you have a Check Engine Light in your car? If so, is it working? Meaning does it light up when you turn ignition on, and then go dark after the car is started.
(B) Unplugging an EHA valve plug during engine running generally triggers the light to go on. Does it? If none of these are happening, that is another sign of inoperable ECU.

Your condition is exactly why I always advocate for an EHA current gauge in the car. With that you do not have to diagnose these things and instead you will be monitoring the ECU behavior from the comfort of your driver seat, 24 hours/ 7 days.