14 replies to this topic

[MR J]

Hi

For about the last 4 years I've had a hesitancy problem with my 94 Spi sprite. Cruising at around 60mph it sometimes hesitates and won't accelerate, lifting off usually cures it and it will accelerate smoothly again.

I have so far replaced all the ignition HT system, lambda sensor, coolant temp sensor, throttle position sensor, cat and 88 deg thermostat but it is still the same.

I have invested in the Mems diag app and hooked it up to my phone and taken it for a run. I have attached some screen shots of the results of driving at about 60mph.

Should the fuel trim reading flat line? As when it flat lines that's where the hesitant problem occurs and what would cause this?

Attached Files

•  Screenshot_20180411-183203_MEMS Diag.jpg   31.36K   7 downloads
•  Screenshot_20180411-184017_MEMS Diag.jpg   30.52K   6 downloads

Edited by MR J, 11 April 2018 - 06:47 PM.

[MR J]

It seems the fuel trim flat lines when it drops to 100, also the map sensor stops at 100 although I think that's it's maximum.

Attached Files

•  Screenshot_20180411-185926_MEMS Diag.jpg   30.23K   2 downloads

[Sprocket]

Can you show a graph with TPS (throttle position) instead of battery voltage?......

[genpop]

can you export your logfile? You have to be admin on your android then you can send the logfile.Then Sprocket  may be able to help!

[MR J]

I figured out after the run I could add extra trends. Will have another run tonight and post details.

It's one of the reasons I replaced the TPS, although the one I replaced the original one with is used also.

[MR J]

Think I may be slowly tracing my problem. I've borrowed another ecu just to eliminate mine and been for another run but I have simiĺar results.

Only this time the fuel trim is pretty stuck at 100% all the time and it seems to not change over to closed loop.

I had a fiddle with the lambda sensor connection and it jumped into closed loop and the fuel trim then started responding. It ran fine for a few minutes then dropped out again but fiddling with the lambda connection again makes no difference.

[MR J]

Think I may be slowly tracing my problem. I've borrowed another ecu just to eliminate mine and been for another run but I have simiĺar results.

Only this time the fuel trim is pretty stuck at 100% all the time and it seems to not change over to closed loop.

I had a fiddle with the lambda sensor connection and it jumped into closed loop and the fuel trim then started responding. It ran fine for a few minutes then dropped out again but fiddling with the lambda connection again makes no difference.

Attached Files

•  Screenshot_20180413-142042_MEMS Diag.jpg   27.98K   0 downloads

[MR J]

Think I may have found the culprit. If it is I can't believe I'd never looked at changing it.

 

Attached Files

•  Screenshot_20180413-161442_Photos.jpg   26.92K   0 downloads

[MR J]

Maybe not, still having problems with it switching in and out of closed loop.

Attached Files

•  Screenshot_20180413-190649_MEMS Diag.jpg   28.74K   1 downloads
•  Screenshot_20180413-190802_MEMS Diag.jpg   27.88K   1 downloads

[genpop]

why don't you publish the logfile

[MR J]

I don't know how to

[MR J]

Here's a few more screen shots if anyone interested

Running fine one minute, stuck in open loop the next.

These are all at idle and sat revving

Attached Files

•  Screenshot_20180414-125848_MEMS Diag.jpg   28.91K   1 downloads
•  Screenshot_20180414-130632_MEMS Diag.jpg   15.07K   1 downloads
•  Screenshot_20180414-131629_MEMS Diag.jpg   19.46K   0 downloads
•  Screenshot_20180414-131949_MEMS Diag.jpg   20.8K   0 downloads
•  Screenshot_20180414-131754_MEMS Diag.jpg   24.88K   0 downloads

[MR J]

Would the experts say this is a dodgy lambda sensor?

Just sat idling

Attached Files

•  Screenshot_20180414-145738_MEMS Diag.jpg   19.84K   3 downloads

Edited by MR J, 14 April 2018 - 04:08 PM.

[genpop]

I don't know how to

on the three dots in right upper corner you may set the preferencies for mems diag.There you can set a prefix for log-files.Type for example mini-log. After return you can start the log by toggle log.Here you may stop it too.

Then you need a file manager on your android.There are some for free in the play store. Or you have one already. Search in main memory .directory  mems-diag will be found.There is your log-file. Send it to your email adress. Open mail on pc and publish it.If you have microsoft excel, you may import it as .txt file and have a look to the values yourself.

[MR J]

Replaced the 2 year old lambda sensor with my 24 year old Bosch one and car is now running great.

 

Took for MOT today and sailed through emissions without a problem