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Spi Running Rich


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#1 Stumac1

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Posted 26 May 2020 - 05:22 PM

Hi there any help would be very much appreciated.
Have just done an engine rebuild on my mini and added on some goodies (new cylinder head with bigger valves, sw5 cam, lightened flywheel). I’m now struggling getting the car to run properly. I could not get it to run at all at idle although it tried, so i’ve opened up the throttle on idle on the stepper adjustment. It now runs but very rich even causing some smoke to come out the inlet manifold. I’ve check the vacuum lines but cannot hear a leak nor see any broken pipes. I’m going to try reset the valve clearances as i haven’t done this yet, any other ideas as to why it could be running so rich?

Thanks alot
Stuart

#2 MatthewsDad

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Posted 27 May 2020 - 11:51 AM

How did you adjust the idle speed - was it using the screw in the throttle body? Not sure whether that screw should normally be adjusted. Did you change the vacuum hoses and sensors during the rebuild?

#3 Stumac1

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Posted 27 May 2020 - 12:26 PM

Thanks for your response. Yes adjusting the screw on the throttle body, its the only way i could get enough air in to get it to run. I’ve changed a couple of the plastic vacuum hoses due to the elbows cracking. I’ve replaced the lamda sensor and the coolant temp sensor also. Before rebuild the coolant temp sensor was linked out by a previous owner but i’m unsure why.

#4 cian

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Posted 27 May 2020 - 12:52 PM

What o2 sensor did you fit

#5 Pops_Guild

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Posted 27 May 2020 - 01:37 PM

I get why you might adjust it, because it does appear to solve a problem, but that screw shouldn't be adjusted unless you have the appropriate reader device to plug into the ECU port, the reader will instruct you on how to adjust that screw. Adjusting it without any of that will not fix your Mini's problems unfortunately as it needs to go in tandem with the stepper motor and ECU adjustments.

 

I think above all advice, you need find someone local to you who has a decent reader setup and knows how to use it. It will also tell you if any of the other important components are reporting errors any fault with the temp transmitter/sender, air filter temp, crank sensor will also cause the ECU to go into limp mode, which over fuels. You've changed some big things there so you really need all the other parts to be in tip top condition in order for the ECU to be able to learn what your new engine setup needs. The SPI setup is pretty good at this but you need to give it a fair chance :).

 

As mentioned above faulty vac pipes are common reason for poor fuelling. Even if they look fine, if you haven't replaced them in a few years, it would pay you to do so. They were a service item and critical to the health of an SPI.

 

Assuming all of these are tip top and no errors, did you intialise/reset the stepper motor and set the lost motion gap? Again this is essential if you have disturbed the accelerator cable. This is the point when the ECU can start relearning the engine.



#6 Stumac1

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Posted 27 May 2020 - 07:35 PM

Thank you, i’m aware that i will need to reset the stepper motor and will do per the haynes manual. I’ve also ordered a code reader which im hoping will give me more of an insight as to what is going on.
From what you’ve said i think it must be in limp mode as the amount of fuel the injector is spraying seems to be vastly more than what it should be.
I’ll have another check of the vacuum lines, and the various sensors you’ve mentioned. Again cheers for your help, hoping i haven't done any damage due to the over fuelling.

Cian, its just the standard mpi/spi lambda sensor.

#7 Pops_Guild

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Posted 27 May 2020 - 09:20 PM

Thank you, i’m aware that i will need to reset the stepper motor and will do per the haynes manual. I’ve also ordered a code reader which im hoping will give me more of an insight as to what is going on.
From what you’ve said i think it must be in limp mode as the amount of fuel the injector is spraying seems to be vastly more than what it should be.
I’ll have another check of the vacuum lines, and the various sensors you’ve mentioned. Again cheers for your help, hoping i haven't done any damage due to the over fuelling.

Cian, its just the standard mpi/spi lambda sensor.


Stu - didn’t mean to come across as harsh, we’ve all been through learning curves just hoping to help you get there quickly. Your engine should be ok. Glad you have a plan, just take your time, be methodical and it’ll come good I’m sure

#8 Stumac1

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Posted 27 May 2020 - 09:29 PM

Not at all ? i’ll get there eventually!

#9 brivinci

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Posted 27 May 2020 - 11:23 PM

I hope that its just the limp mode causing the issues. A code reader is a VERY handy thing to have if you own one of these. At the very least, it takes a few of the possible issues out of the equation. 

 

While you are in there, replacing the vac lines/elbows with proper 3mm-walled silicone hose. Although nothing is perfect, in theory it should be. Much more reliable then the standard type which can fail at multiple points. Its just nice to not have to guess whether these super important lines have a hairline crack somewhere, or an elbow that might be on its way out and not sealing, or one is too close to something hot and is melting...you catch my drift:-)



#10 cian

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Posted 28 May 2020 - 04:20 AM

If you put in an aftermarket sensor they do not work and will stick at a rich mixture

#11 Stumac1

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Posted 28 May 2020 - 03:40 PM

Right so today i have changed over air filter with the original MAP sensor, i replaced the vacuum line from fuel trap to ecu with 3mm hose. The car now runs a hundred times better and i’ve been able to shut that stepper throttle adjustment right back to where it was originally. The only issue now is the idle is a bit up and down so i’ll reset the stepper motion position and hopefully that’ll sort it?

#12 brivinci

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Posted 28 May 2020 - 04:58 PM

Thats great news! These cars can be weird...






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