82 replies to this topic

[viz139]

You will find the correct wiring diagram for your car here in the first post below the main list.

http://www.theminifo...agrams-redrawn/

 

I had a similar high idle problem but my temperature gauge was showing very slightly below normal (top of the needle at bottom of white line). The connector had come off the manifold heater and once reconnected all was ok. I was surprise to learn that the heater was on with a warm engine but it made a difference

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[Robbie693]

Thanks for that, very useful.

 

I'm unsure of what to do next - If I take the ECU to be checked off the car there could be another faulty sensor I have missed which will still be there when I refit the ECU. If it is the lambda heater circuit at fault surely this would only cause problems during warm-up, such as a misfire?

 

If I just take the car to be put on a diagnostic I don't know if the ECU itself will show as a failure?

[Robbie693]

Right then.,,,  the saga continues.

 

I took the ECU to ATP for a check and they confirmed the suspected lambda heater problem and another problem with the fuel pump circuit but said they couldn’t find anything that would cause the idle symptoms I am getting. I had them rebuild it anyway to eliminate variables and I’ve put it back on the car but the problem still persists.

 

I have got hold of MEMS Gauge, MEMS Scan and MEMS Analyser and checked for faults. Initially, after refitting the ECU there were 3 error codes stored (coolant temp, air temp and fuel pump circuit). These I cleared with MEMS Gauge and they have not come back after a few runs. 

 

I tried MEMs Scan as it gives a bit more information and all the error codes were clear. The only anomaly it recorded was an ‘Unusually Low Lambda Signal’ pic - 

 

 

 

 

 

 

This anomaly disappears after re-starting the program.

 

 

The live data saw the Lambda voltage swinging between about 80 to 890 mV

 

Other values were, with engine idling about 1400rpm, 

 

manifold pressure around 30kPa. 

 

coolant temp about 84 deg c, 

 

throttle pos 12%, 

 

idle air motor position 0%

 

I recorded a couple of log files, the one from MEMS Scan isn’t recognised by MEMS Analyser and the ones from MEMS Gauge look corrupted to me - the information is a clear graph like the example files. At first I thought it was because the pc ran out of battery during the recording but the next on was the same. I have attached them anyway incase someone can make sense of them - perhaps I am doing something wrong.

 

So I am mystified as the cause of the problem, surely anything wrong would show up as a fault on the diagnostic information?

 

 

Attached Files

•  mems gauge results 1.txt   67.7K   5 downloads
•  mems gauge results 2.txt   43.52K   2 downloads
•  mems scan results.txt   355.18K   3 downloads

[genpop]

Download mems-rosco from github.com/leopoldg .You may analyze all your logfiles. On a short look, your lambda is working now, lambda status is ok and closed loop is ok.Watertemperature should be higher.Check your thermostat should be a 88degree one. What you realized already ,IAC is too low, should be 10 to 15 at least and TPS should be 0,5 V. Correct the idle air at the screw you should not touch.

Engine has to be at highest temperature., If TPS does not regulate to a lower value then open both screws and try to turn the sensor.And at least you could set rpm in mems scan as well as in mems rosco.If nothing of all these suggestions work you may reset ecu in mems scan as well as in mems-rosco.

[Robbie693]

Thank you, I need to do some studying - I am at the limits of my understanding at the moment! I'll have another look at the logfiles with mems-rosco.

 

The T-stat is an 88 deg type. I assumed the temp didn't get any higher as it was only idling in the garage and the weather was particularly cold today. How would I make the engine run any hotter?

[genpop]

So I read the complete thread again. I wonder why ecu switches to closed loop even when temperature is not at 88 degrees. But it switches so you  may not worry about temperature, it was only a hint.

Before you start with my suggestions in my last post read this thread:http://www.theminifo...otor-operation/

Take the IAC apart, clean it and measure the single coils in there on their ohm values.If the problem still exists do my suggestions.

Attached Files

•  Steppermotor.JPG   61.64K   5 downloads
•  Stepper messen.JPG   72.4K   4 downloads

Edited by genpop, 29 January 2020 - 07:38 AM.

[Robbie693]

Yes I was thinking about the same thing last night (trying to sleep!), it occurred to me that as the idle air screw has never been touched in the car's life, why would it need adjusting now if were not to compensate for something having failed or degraded. So I thought about the stepper motor, particularly as it is the only thing that doesn't have a fault code on the mems scan.

 

In the thread you linked to, there is talk about cleaning out the stepper as well as testing the electronics - how does one clean the stepper motor?

[genpop]

I wrote "Take the IAC apart, clean it", There are some mechanical parts inside, you can clean and grease them! Maybe you can clean inside the motor by air blast.

Sprocket wrote, mostly only the solder spots have to be renewed and he sets the steps to 30.

Edited by genpop, 29 January 2020 - 11:07 AM.

[Robbie693]

Ah you mean the actual mechanical linkage bits - ok understood.

 

I can't find instructions (on forums or in the manuals) of how to remove the stepper but it looks like I need to remove the injector housing to get at the torx screws, so I will need to get a new gasket. In the meantime, circuit boards are a mystery to me - I can't tell which solder joints I should be probing to test the winding resistances?

[genpop]

Normally you don't need a new gasket.

You measure ohm between 2+3,2+1,2+6,,2+4.You may do that on the socket or on the circuit board.

Its best you resolder all conections.

Attached Files

•  IAC.png   96.88K   5 downloads

[Robbie693]

Just as well about the gasket - looks like they are obsolete.

 

So 2 is the common - in your photo above is the black lead on terminal 2?

 

 

Does this mean I could do an initial check using the pins in the connector and not have to dismantle the stepper housing?

[genpop]

Does this mean I could do an initial check using the pins in the connector and not have to dismantle the stepper housing?

I think so. But then twist the cable and do some more checks.

[Robbie693]

Great thanks. Should be able to have a look tomorrow.

 

I was looking at these screenshots of my first run with the MEMS Gauge program and it shows, as you say, the idle bypass position gradually reducing to zero as the engine warms, on the display there is a number (51 in the first pic) is that the number of 'steps' the IAC is at? I understand that it should be around 30 steps with a warm engine, (or 15% as you say), is there any reason why I shouldn't move the closed/open slider to increase the stepper motor setting?

 

 

 

 

 

 

 

 

 

[genpop]

Too long ago that I worked with mems gauge. This setting works with steps of 25%.But you may try.

[Robbie693]

More discoveries...

 

Checked the resistance at the pins and got around the 14.3 ohms for middle to all others. Also checked all others to all others and got about 28.5 ohms.

 

Before I started I plugged in mems gauge to see what the position of the stepper was at when cold - it was at 149 steps (82%)  I also have low battery voltage possibly from stop/starting and running at idle in the garage- 

 

 

 

As I understand it this is way to many steps for a cold engine?

 

 

I checked it was moving freely and it is. Here are pics of the plunger at cold with the ignition on and off - 

 

 ign on cold.jpg   43.18K   5 downloads

 

 ign off cold.jpg   43.83K   3 downloads

 

 

 

So something is going on, almost like it has got confused. I keep thinking this all stems from the alternator failure I had.

 

 

So in MEMS Scan there is a button - "ECU Reset" - what happens if I press it?

 

 reset.jpg   69.01K   1 downloads