21 replies to this topic

[eero]

Greetings from the Estonian Mini Club! I just joined up because the technical expertise of some of the members here seems to be amazing. Thanks for sharing!

 

Anyways, my '93 SPi is acting up a bit. It has really rough idle when cold, usually cutting out in a few seconds, and hesitates a bit when accelerating, either cold or warm. I've been through the topics here, have cheked for most things and am now awaiting delivery of a fault code reader to get to the root cause, I suspect there is a sensor at fault.

 

But my question is about a certain screw mention by Sprocket here: http://www.theminiforum.co.uk/forums/topic/20533-having-problems-with-spi-single-point-injection/?p=241579 I've been up and down the injection, changing the vacuum, breathers etc, adjusting the throttle. So of course I "had" to adjust this screw as well.

 

 

Any tips how one could adjust it without proper diagnostic tools to more-or-less acceptable running condition? And with a diagnostic device, what's the process like?

 

 

Cheers!

Edited by eero, 02 September 2013 - 03:20 PM.

[FlyingScot]

Hello eero, as you have read Sprockets post, you will understand that there is no way to adjust the screw without the diagnostic kit.

I wouldn't mess with it any more as the poor running needs to be properly diagnosed and you stated you have some equipment coming. Many faults with these cars can be down to just simple things, air leaks, vacuum leaks and poor electrical connections. So please check everything you can until your equipment arrives.
What kind of diagnostic equipment have you bought?
Your car sounds like an early SPI so it will probably be able to be " tuned" if you have the Crypton ACT (shown in sprockets post) or a sykes pickavant ACR with Rover pod 1.

FS

[Island Mini]

this is just a question I've had for a while. If someone posted a close up of a properly adjusted screw on the same size engine with no extra ancillaries to provide extra load could you not just adjust from that? or measured the gap using a verneer caliper 

[FlyingScot]

The system works by the stepper motor indexing through the full range of movement on sequence and the screw we are discussing sets one of the fixed positions. The MEMs unit then calculates what position the stepper should be in (for idle) bearing in mind the coolant temperature and inlet air temperature and steps the motor thorough the number of steps to achieve this.
The screw doesn't set the idle speed as such but affects the number if steps the MEMs calculates the idle position of the stepper should be.
As this will be different for each engine and conditions (worn, rebuilt etc as well as the environmental conditions) I don't think the position of this screw will necessarily be the same. This is the reason that it is recommended to use a diagnostic reader to set it up, as the reader tells you to adjust the screw to achieve the right position (within 30 secs from memory ).
It should be remembered that this stepper motor is opening a small valve to bleed in air and works in conjunction with the other things the MEMS does with the ignition timing to keep the idle speed right under all the conditions found by the car.
In reality it's a kind of back calculation for the position of the screw.

FS

Edited by FlyingScot, 03 September 2013 - 08:47 AM.

[FlyingScot]

The MPi system works in the same way excepting the inlet air control valve (which does the same function) is a separate unit with a kind of plunger inside. The air flows through this valve and through the connecting tubing (hose) as it is external unlike the SPi.
This plunger can get all gummed up with deposits effecting the control the IAC valve has, some people recommend cleaning it with carb cleaner

FS

[Island Mini]

I understand what you're saying but the method I described would this not be the best solution for people like me who don't have access to a diagnostic where we live and a previous owner has adjusted the screw? 

[FlyingScot]

I understand your problem but how can you be sure all the other sensors are working as they should on either your car or the one you have the picture/ measurement of?
The stepper motor on an SPi has 180 steps (although the effective range is 150) and controls 2 things, the small inlet air valve (pintle valve) and the throttle flap on the main body of the injection unit (through the linkage ); this is to provide fast idle under certain circumstances. None of the settings are truly independent in the way the system works, this is why you need to have a logical approach step by step to solving any of the issues.
I hope your method does work, it may give a starting point for further "adjustment".

FS

Edited by FlyingScot, 03 September 2013 - 09:52 PM.

[eero]

Your car sounds like an early SPI so it will probably be able to be " tuned" if you have the Crypton ACT (shown in sprockets post) or a sykes pickavant ACR with Rover pod 1.

 

I have a Sykes Pickavant ACR with pod v1 on they way. Fingers crossed it shows something to work with. Though I'm slowly starting to think my issue might be related to bad connections, because I noticed a bit of a change the moment I turned the headlamps on. Not much has been done to the electrics over the years. I'm going to measure the voltage on all possible connections and see what it shows.

 

 

But about the screw...

 

I totally agree with FlyingScot, that small adjustments could make a world of difference and achievening a finely tuned machine this way would be nearly impossible. But once it has been mucked up anyways, wheres the harm? 

 

So if anyone is willing to take a measurment and share it, that would be great. Or one could go and count the threads on Sprockets picture

[eero]

Ok, scrap the last idea... Went and had a look at the Sprockets post and there are two different images showing the screw, two different injections by the look of it, and the screws are a world apart. Might as well just use patience and approach systematically - say a quarter or half turn every day and see what happens.

[eero]

Ok, this is getting a bit off topic, but I don't feel this quite deserves a new post. Sorry, if anyone came looking for definite answers about the Screw

 

But going through the electrics today had some results (though it was not electrical). As described by Sprocket, I started to check the lambda.

 

And the moment I squeezed the return flow, the engine came back to life. Result! Although pressure was checked in the summer, it seems we missed something and it's clearly the pressure. So now I need to look either at the injection or the pump.

 

I tightened the return with a hoseclamp as a temporary fix (is that safe?) to compensate and had a nice test drive. Probably better than ever - seems to run nice cold, no hesitation.

 

And back to the topic - though idle is now stable as if the needle was glued to the dial, it's a bit high (~1000rpm). So probably the screw now needs adjustment, but I'll probably wait for my diagnostic unit to arrive for that.

Edited by eero, 04 September 2013 - 07:43 PM.

[Island Mini]

Sounds like the fuel pressure reg diaphragm is done for or needs cleaning since its obviously letting through too much fuel to the return hence why clamping it is forcing more fuel through the injector or you're running lean for some other reason. I'd start by taking the reg apart

[eero]

Sounds like the fuel pressure reg diaphragm is done for or needs cleaning since its obviously letting through too much fuel to the return hence why clamping it is forcing more fuel through the injector or you're running lean for some other reason. I'd start by taking the reg apart

 

Sounds like a plan! Any suggestions what I should look for or just a basic cleaning? Or could it possibly be replaced? Though I can't find it mentioned as a replaceable part, let alone anyone selling one.

[Island Mini]

Umm just make sure it's all functioning properly diaphragm hasn't started to decompose and is sealing properly. To get a replacement one I think like getting an injector you'd have to get the whole manifold and pull the bits off. Probably not a bad idea as you can then rule out your coolant temp sensor and a faulty injector possibly which might cause the issues as long as your lambda sensor is good.

[FlyingScot]

If the OP is getting an ACR unit he will be able to check the sensors for faults....and read live data. Best to start with facts

FS

[Island Mini]

What he said.

But just check its nothing obvious in the reg anyway