34 replies to this topic

[BritOP94]

Hi everyone! I'm currently trying to put my freshly restored 95 Spi back on the road but after days of troubleshooting and just cannot pinpoint what's wrong with it... So I'd love to get some help from all the injection gurus from here!

 

Engine is freshly rebuilt and so is pretty much everything on the car but I'm experiencing some starting and idling issues. To help with the troubleshooting I've sorted out a fault reading setup with memsFCR and will try to give as much data as possible.

 

From cold, it takes quite some cranking to eventually get it to sputter and it needs to be revved a bit not to stall on and after the initial cold startup. 

 

Eventually (after some light rev helping) it will idle rather roughly at around 1300rpm and IACV at around 60-65 steps. If I let it warm up (reaching 85-88°c), the revs will lightly drop at around 1200rpm and the IACV @ around 49 steps. Idle at this stage is high but stable.

 

MAP at idle 26-30kPa - lambda between 200-700mV - STFT between 26 and 29

 

If I kill the engine and try to restart it at this point it will start a lot easier than cold but will still need to be helped not to stall initially.

 

When fully warmed up (88-90°c) if I either try to adjust the IACV (which sits at 49 and doesn't move anymore unless given some throttle) or give it some revs (to which the engine responds very nicely) the IACV just drops straight to 0. Idle drops a bit too, engine struggles and eventually stalls if I don't maintain some rpms. 

 

MAP still at around 25-26kPa - lambda 200-700mV - loop is closed - STFT around 23-26

 

Now at this stage, if I "trick" it into staying at a fixed 35 steps with the memsFCR, it idles fine at around 900rpm, no faults, everything going steady...

 

But obviously once I disconnect the FCR and let the ECU deal with the IACV it drops straight back to 0 and stalls again. 

 

I've checked the IACV operation and coils resistance values and everything seems fine, I've tried and tested some different IACV units as well but it does the same thing.

 

I've also checked the throttle position sensor, resistance values are also spot on and also does the same thing with some different 2nd hand sensors (tested too)

 

Tried swapping the crankshaft position sensor as well, doesn't help.

 

Checked the ignition coil and swapped it, doesn't help.

 

Fuel pump is priming and can be heard when the car is running.

 

Oxygen sensor is brand new and the heater relay clicks fine.

 

I've checked every hose and vac line (most of them are new anyways), plugging some etc and it doesn't change either

 

Oh and I've taken the car out for a couple of short spins when the idle is stuck @1300rpm and 49 steps (that way it doesn't stall) and the engine pulls nicely through the rev range. It's really just that idle and cold/hot starting issue.

 

Any help or direction would be incredibly appreciated... 

 

 

[genpop]

log-file?

[BritOP94]

I'll upload some asap, csv files are fine?

[BritOP94]

memsfcr two csv logs recorded yesterday, hope this helps

 

[MatthewsDad]

You don't mention any work on the throttle body. Did you replace the gaskets?

[genpop]

Either your lost motion gap is not set right or the potentiometer is not working right. Even when iac is down at 50 the throttleangle is always higher then 9,6, it should be down at 0,5 to 0,6 when idling.When having corrected that do a new logfile

[BritOP94]

 MatthewsDad : Should have mentioned it sorry, yes I did.

Edited by BritOP94, 16 June 2025 - 05:33 PM.

[BritOP94]

Either your lost motion gap is not set right or the potentiometer is not working right. Even when iac is down at 50 the throttleangle is always higher then 9,6, it should be down at 0,5 to 0,6 when idling.When having corrected that do a new logfile

I'll double check and post the new log tomorrow, thanks

Any tips on checking the throttle pot condition? I measured it's resistance from closed to open (that was on par with the values I found here, 0.9 to around 5k if I remember correctly)?

[BritOP94]

Ok, managed to get a couple of new logs this morning. memsfcr

I adjusted the lost motion gap following the procedure (ignition on, reset IACV with a full throttle movement at the throttle body, IACV resets itself to 35 steps, adjust lost motion, then ignition off keys out). 

I named the logs to help differentiate them

The new logs include two from the initial cold start with no help, it did stall after some time.

Then a long one when it was warming up, ends with me turning it off, it didn't stall.

Then one when I tried and restarted it, struggling and super long cranking, eventually sputtered into life. You should see there's some throttle input from me, steps goes up with the throttle, stay high for a bit then again drops to 0. Tried adjusting the IACV screw as the idle was kinda steady but you'll see it died straight at the end when I did.

 

again hope this helps, and thanks a lot for everybody's valuable time and input!

[genpop]

I didn`t have the time to diagnose your logs up to now.Please ask Andrew Jackson the owner of mfcr for setting the carburator, he had a manual for this on his web side ( I can not find it any longer).

But I have a simular one for other TBI`s possibly this will help.This is for a spindle IACV but you may use it on a stepper too.

Attached Files

•  basic setting.txt   3.84K   8 downloads

Edited by genpop, 20 June 2025 - 10:31 AM.

[genpop]

Have a look why the butterfly does not close.6 degrees means high idle no further setting posible.

[BritOP94]

Ooooh ok, that definitely makes a lot of sense... I'll follow that .txt and see if I can get it to behave better, and the always slightly opened butterfly would explain a lot, I'll investigate asap

[BritOP94]

Ok, sooo...

Bit of a daft question, but I can't find the "target idle speed" anywhere in my ECU data... This is all I'm getting with MemsFCR

Should I be able to extrapolate it using the data I've got? Or use a different fault reader?

 

 Screenshot 2025-06-17 173202.png   147.58K   1 downloads

[genpop]

target idle speed is the speed you want the engine to idle ,in the case of a mini its 850rpm

or if you read the actual rpm minus idle speed deviation that should be 850 again.

[genpop]

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.