39 replies to this topic

[BritOP94]

at a second glance to your logfile i realized that the ecu does not switch to closed loop and the water temperature does not reach 88 degrees.Check your thermostat too.

by the way.You could download mems rosco from github.com/leopoldg/mems rosco itwill read your mfcr logs as well und show them as graphs and like excel lists.In its directory there is a small manual (pdf) what shows the possibilities of mems rosco.

I haven't had a chance to try and set the idle right this morning but I did overhaul another manifold I had and installed it (After what you said about the butterfly and the idle pot voltage I had a bad feeling about the old one), I'll run the full set up procedure tomorrow and report back.... 

 

About the temp, it did get to 88 and slightly over (like 92) during the previous tests, but it takes a while to do so... Thermostat is a tested and working 88° (or 82°, not sure now that I think about it) unit from my other Mini.

 

Closed loop kicks in when the ECU sees precisely 88°c at the coolant temp sensor? or is there any other factors?

 

I'll check Leopold's program too,thanks! 

[BritOP94]

Ok so quick update as I had spend quite some time again today trying to sort things out.

 

I tried to correctly set the IACV again (as described in genpop's txt file)

 

Cold start : not that bad, had to help with the revs a bit as it initially really wanted to stall but eventually managed to get a stable-ish high idle at around 1300rpm, went for a quick drive around the block to get everything warmed up.

 

As mentioned, it actually goes really nicely, doesn't feel lumpy, pulls through all gears well and smoothly.

 

Got back, plugged the computer: water temp around 90°C, got into closed loop this time, throttle pot 0.56v at idle, but the IACV is still switching 0 and and usually around 49. 

 

I followed Genpop's procedure, then checked the lost motion gap again, but the main problem is still there : it feels like the IACV is just kind of "giving up". when fully warmed up, it will only sit at a higher number than it should, then suddenly drop down to 0 which makes the engine surge and stall if not helped with the throttle. A blip of the throttle brings up the rpms, the IACV follows too and climbs, but when it tries to get back to a stable idle, the IACV drops back down to zero etc... 

[genpop]

so i found this on Jacksons webside:https://memsfcr.co.u...-stepper-motor/

 is this your second tbi device? then sometimes ecus are bad too.

In the german forum is a member mini guido, he offers checking and repairing ecus, in GB there are some firms offering this job.

if you still work with your original tbi i would check the solder points of the stepper motor!

[BritOP94]

so i found this on Jacksons webside:https://memsfcr.co.u...-stepper-motor/

 is this your second tbi device? then sometimes ecus are bad too.

In the german forum is a member mini guido, he offers checking and repairing ecus, in GB there are some firms offering this job.

if you still work with your original tbi i would check the solder points of the stepper motor!

Yes, that's what I tried originally... But again, impossible to adjust anything since the IACV value just drops straight from 49 to zero with even the slightest touch... 
And yes, I've actually got a couple manifolds, either complete or in parts (some stepper motors too), I'll check them again, but other than the general aspect of the solder points and the coils resistance, is there any other way to tell if a motor is good or bad? The couple I've tested seemed fine, I could manually (with memsfcr) add or remove one step at a time and it didn't seem to skip

[BritOP94]

Oh and about ECUs, I might consider that as the last step yes... Dumb question, but they are straight swappable between two similar cars right? I do have another ECU taken from a 100% working car, but from what I remembered the IACV issue was still present with the other ECU

[genpop]

in this case you should double check the main ground cable fom the chasis to the ecu and the cable from the chasis to the engine.As well check the cables from ecu to the stepper.Some others reported broken cables there.

[BritOP94]

in this case you should double check the main ground cable fom the chasis to the ecu and the cable from the chasis to the engine.As well check the cables from ecu to the stepper.Some others reported broken cables there.

Okay, so I pretty much spent the day working and testing stuff on the Mini... 

I did test the wiring from the ECU to the IACV plug and the main earth too, they all seem ok, continuity through all the wires and around 0.2 ohms across both plugs. Tried running a jumper straight from the battery negative to the engine too but that didn't seem to do anything.

 

As mentioned, I tried swapping the IACV for another one, I checked the soldering on that one and it looks good, I measured the resistance across the pins of the IACV coils and I'm getting 0.15ohm from pin 2 to all the others, and 0.30ohm between all the other pins except pin 2 (which I think is how it should be?). But again, that didn't seem to do anything.

 

Also tried again with 2 different ECUs, didn't help either. 

 

Here on this graph you can clearly see the issue, but I feel like I'm missing something really obvious... 

 

 Screenshot 2025-06-22 172914.png   76.74K   1 downloads

 

The IACV is basically always returning to either 0 or 49 steps PRECISELY as some sort of default position, you can see how it reacts to throttle input but will always settle down to 0 or 49, depending on how far the adjusting screw is set.

 

 Screenshot 2025-06-22 171241.png   55.84K   1 downloads

 

But I can still set it to 35 for example using the diag tool. But it won't do it on it's own.

[BritOP94]

Despite the temp readings looking spot on, could there still be some kind of partial issue with the coolant sensor?
The only injection specific elements I haven't swapped or tried to diagnose so far are the inlet manifold and what's on it (coolant sensor, heater unit and the manifold itself) and the wiring loom (which I might actually try to replace with another one)

[genpop]

I am nearly out of ideas!

Here:https://www.mini-for...c5-steppermotor

you see the ohm readings on a good stepper and which points to take.

As the water temperature curve rises staedy i don't think that it is the thermostat.

if it is a1992 you could check the gas pedal switch (flood it with wd40,or simular).I have never tested what hapens on idle when this is not working!

Test the loom from ecu to stepper again.If I have further ideas I will write but it has something to do with the IAC.

If you have an oszyloskop you could test the wires to the IAC while running.

[BritOP94]

I am nearly out of ideas!

Here:https://www.mini-for...c5-steppermotor

you see the ohm readings on a good stepper and which points to take.

As the water temperature curve rises staedy i don't think that it is the thermostat.

if it is a1992 you could check the gas pedal switch (flood it with wd40,or simular).I have never tested what hapens on idle when this is not working!

Test the loom from ecu to stepper again.If I have further ideas I will write but it has something to do with the IAC.

If you have an oszyloskop you could test the wires to the IAC while running.

 

Oh nice! Loads of very useful values to compare with! 

And yes, I don't think the thermostat is problematic, I was more thinking of an issue of some sort with the coolant temp sensor under the manifold (even though it appears to be reading fine).

It is a 95 so no throttle pedal switch I'm afraid.

And yes, I'd be more and more inclined to believe there's a wiring issue somewhere in the injection loom. Might need to get the old Tektronix osc out haha

One last thing, do you have by any chance a log file of a proprely idling spi? I'd like to double check some throttle angle/pot values...

 

Again, thank you so much for your time, much appreciated! 

[68+86auto]

Underneath the SPI setup is an engine that functions exactly the same as every other petrol engine. This means that problems can be diagnosed the exact same way. Many people believe that a scan tool replaces proper diagnostics, it doesn't. This applies to ALL cars.

The correct procedure is to test the starting, ignition and then fuel systems in order to determine what is happening. When something is discovered that isn't functioning normally, tests need to be done to determine why. The signals in and out of the ECU need to be tested on an oscilloscope to ensure they are correct.

The ECU doesn't know when there's a mechanical issue and will constantly try to compensate.

You say you've tested the earths but from what you've said, you have done this in a way which doesn't fully test them. The best way is to measure the voltage across the earth, the result should be less than 0.1v. Resistance doesn't take into account what happens under load.

Edited by 68+86auto, 22 June 2025 - 11:05 PM.

[BritOP94]

Underneath the SPI setup is an engine that functions exactly the same as every other petrol engine. This means that problems can be diagnosed the exact same way. Many people believe that a scan tool replaces proper diagnostics, it doesn't. This applies to ALL cars.

The correct procedure is to test the starting, ignition and then fuel systems in order to determine what is happening. When something is discovered that isn't functioning normally, tests need to be done to determine why. The signals in and out of the ECU need to be tested on an oscilloscope to ensure they are correct.

The ECU doesn't know when there's a mechanical issue and will constantly try to compensate.

You say you've tested the earths but from what you've said, you have done this in a way which doesn't fully test them. The best way is to measure the voltage across the earth, the result should be less than 0.1v. Resistance doesn't take into account what happens under load.

 

Hi and thanks for the input! To be honest it's the first time I actually have to use a diag tool on a Mini, I'm much more familiar with the non-MEMS ones... 

 

As far as the starting system goes, I can't see much wrong with it, the starter's electrical draw is a bit on the heavy side (replacement is on its way though) but nothing out of the ordinary.

 

Ignition wise, being an SPi I don't really know can be tested that's not computer controlled? Leads, plugs and rotor are new, and the cap looks fine, I've cleaned all contacts before fitting too... anything else that could be checked?

 

As for the fuel system, tank is clean, pump is new, so are the filters but it doesn't feel like fuel starvation though... I've tried to check what I could with the evaporation system (lines aren't clogged, I've replaced most hoses and the purge valve and its relay are in working condition)

 

Again, if there's anything else that I could check please let me know!

 

And I've just checked the earthing, main block to body strap, engine running, sees around 15-20mV

 

Might check when hot though

 

EDIT: And yes, the oscilloscope is definitely coming out now...

Edited by BritOP94, 23 June 2025 - 06:20 AM.

[genpop]

Some additional ideas: make a new log file

1.without starting (engine not running) step on the gas pedal one time smooth, second time quick

that will let us see if the throttle poti works fine

2.when engine is running take of the vacuum (map) line from the ecu close both inlets ( map sensor and line)

map should be 100 then

3. take of vaccumline at the throttle body and close both inlets

map should be 100 again and lines and fuel trap are ok

if you have a second voltmeter ,connect it to the generator and watch it when iac jumps.

it is reported that fluctuation in volt supply can have influence on iac

for safety you could change the water sensor too.

Why is the rpm staying stable even when iac drops to zero,when you did the bassic setting you set it to 720 when iac is zero

no further play there?

logfile please

ps: you can shrink and extend the graph with the mouse wheel!

Edited by genpop, 23 June 2025 - 10:08 AM.

[BritOP94]

Some additional ideas: make a new log file

1.without starting (engine not running) step on the gas pedal one time smooth, second time quick

that will let us see if the throttle poti works fine

2.when engine is running take of the vacuum (map) line from the ecu close both inlets ( map sensor and line)

map should be 100 then

3. take of vaccumline at the throttle body and close both inlets

map should be 100 again and lines and fuel trap are ok

if you have a second voltmeter ,connect it to the generator and watch it when iac jumps.

it is reported that fluctuation in volt supply can have influence on iac

for safety you could change the water sensor too.

Why is the rpm staying stable even when iac drops to zero,when you did the bassic setting you set it to 720 when iac is zero

no further play there?

logfile please

ps: you can shrink and extend the graph with the mouse wheel!

I'll try to get some oscilloscope signals from the IAC tomorrow and to do those 3 points you mention as well.

 

I'll check the charge as well, but looking at yesterday's log right now I can only see the slightest variation in voltage as the IAC fluctuates... 14.1 to 14.2v when running.

 

And setting wise, basically what I did after fitting the other IAC was what you mentioned in your procedure (so set iac to 0, unplug, start engine and aim for 725rpm, then switch off etc), but after this set up it still had a rough/no idle, had to give it gas not to stall, and the IAC steps were nowhere near 35, so had to try and adjust it. That's also why the rpm despite being stable are quite high.

[genpop]

did you have a reset of the ecu already and possibly you gave the system not enough time to stabilize itself

 

2500 viewers up to now and no other ideas???????

Edited by genpop, 23 June 2025 - 05:10 PM.