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#1 Frazer stuart

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Posted 17 July 2019 - 06:51 PM

Cooper SPI '93. 120k miles.

My car sometimes stutters at 2000 rpm when I put my foot down. Not always, but if it does it's always at 2000 rpm. I thought I'd use MEMS DIAG to look at the TPS voltage and see if it's notchy around there. It isn't. But I noticed a couple of other things:

1. My lambda voltage never changed from 435. Even when engine was warm and sampling intervals of the app were at 400ms. Isn't it supposed to swing up and down? Anyone else been able to see the voltage swing on MEMS DIAG?

2. My ignition advance moves around loads at idle. When cold it ranged from 10 to 17.5 degrees and was constantly changing. When warm it ranged from 6-10 and still constantly moving. It finally levelled out at 12 20 mins later once it was warm and I'd revved it hard a few times. What could be making my ignition advance behave like this?

Other info - vac lines are all new and in good condition. Fuel trap is new. Lambda is a year old. Car recently passed MOT. I have a maniflow stage 2 lcb and twin exhaust fitted. All 1.75" ID. K and N filter in standard box. It does also have a bit of a wandering idle (since fitting exhaust).

I'm not that bothered about solving the stuttering as it's not a huge problem. I'm just interested really.

Thanks for your help guys and gals!

Edited by Frazer stuart, 17 July 2019 - 06:57 PM.


#2 genpop

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Posted 17 July 2019 - 07:19 PM

do you have the log file?



#3 Frazer stuart

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Posted 17 July 2019 - 07:45 PM

Yeah I do but I didn't know how to upload it

#4 genpop

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Posted 17 July 2019 - 07:52 PM

when you  write a reply ,choose more reply options  on right lower side.A new window will open with your reply.On thr lower side you may attach files.



#5 Frazer stuart

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Posted 17 July 2019 - 07:59 PM

It says that I'm not permitted to attach that type of file :/

#6 genpop

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Posted 17 July 2019 - 08:10 PM

what type is it? normaly mems-diag log-files are txt files.Txt files you may upload.



#7 Frazer stuart

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Posted 17 July 2019 - 08:20 PM

It's a .log file

#8 genpop

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Posted 17 July 2019 - 08:23 PM

rename it .txt



#9 Frazer stuart

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Posted 18 July 2019 - 07:54 AM

Renaming it didn't work for some reason... so I had to use an online converter. Got there in the end! Thanks for your help GenPop.

 

It's just a string of numbers though I don't know how anyone can understand it?!

Attached Files



#10 genpop

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Posted 18 July 2019 - 12:01 PM

must have to do something with either your thermostat or temperature sensor. I think temperature sensor is not working right.After working for a while  it drops to zero Therefore IAC is working  abnormal until temperature sensor reads normal temperatur again. You could log for a longer time if this happens again.Then you have a fault.

Attached is a graph of watertemp , IAC and fault. by the way you can do this graph yourself with mems rosco  (github.com/leopoldg/mems-rosco- download and unzip)Attached File  Frazer.JPG   24.52K   7 downloads



#11 genpop

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Posted 18 July 2019 - 12:07 PM

I`m sorry, current version of mems rosco does not read mems-diag files.Nobody reported that up to now.I have to check whats the fault!



#12 Frazer stuart

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Posted 18 July 2019 - 12:56 PM

Woah those graphs are super helpful thank you so much. I'll do a longer log tonight and see if I can see a fault code. Also, let me know when the Mems Rosco bug is fixed as I'd love to have a crack at this myself. Couple of questions:

 

1. Temp sensor - it was reading temp fine yesterday - on the app I could see it rose nicely up to 90 ish degrees. And I can see it rise on the dash temp gauge too. Sits just below half. What makes you think it's at fault? It's overdue a change so you're probably right, but I don't understand how you've worked it out?

 

2. It's an SPI so am I right in thinking that it doesn't have an IAC valve, just the stepper (sorry if this is completely wrong)? I can hear the stepper click nicely when i turn the engine off, and have seen it moving when i indexed the throttle last, so I'm pretty sure it's all good. (throttle cable adjustment was right on the very end of its thread which was weird though)



#13 genpop

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Posted 18 July 2019 - 03:56 PM

Temp sensor: On the graph you can see that temperature rises smooth but after 1min 30 sec the temperatur drops down to zero.Taht could be the thermostat as well but then I don`t think that it would fall that abrupt.That and that a fault is shown at 2:35 and temperatur drops again makes me think it is the temperature sensor. The faukt is shown in your log file.up to 2:35 fault code is zero after that you have a fault code 32.

IAC on Spi engines is the stepper motor.When temperatur sensor told the ecu that engine is cold ,IAC worked like hell to compensate idling on a cold engine.

by the way up to 1:30 your lambda worked and after 2:35 it worked again.



#14 Frazer stuart

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Posted 18 July 2019 - 04:19 PM

Ah okay that makes a lot of sense. Plus if the temp sensor is telling the ECU that it's cold then it will run closed loop and ignore the lambda. So that could explain why the lambda appears to stop working whilst the temp is reading incorrectly???

I'll run a longer log tonight and see what happens, and I'll try and get the log into mems Rosco.

Thanks again for all the help mate!

#15 genpop

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Posted 18 July 2019 - 04:40 PM

Hi Frazer,

please forget everything I have told you up to now.The graph must have been in memory of my program.After repairing the read-function I got a very different graph.Attached File  Frazer.JPG   47.7K   5 downloads

Now  my question is: is it an older SPI with the idle switch under the gas pedal (ecu with two connectors)Then I would have a look to that switch.Flood it with WD40 or simular.

I have to test some things before I post mems-rosco again. Sorry






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