Kickstart project for a Diagnostic tool

OK so I've got my Windows Lappy back (sigh of relief) and plugged it all in. Here's what I found:

All reading are the same as before. Temps were a little lower as I hadn't run the engine as long (apart from ambient which was still super high).

1. Unplug the ambient air temp sensor and the engine bay fan comes on. Plug it back in and the fan stays on! The fan only goes off if I turn the ignition off then restart the car... Also if I put a continuity test across the sensor pins it reads up and down every second even if the sensor is out of the engine bay... dodgy sensor maybe?

2. The O2 sensor voltages - sensor 1 wows up and down, sensor 2 is stable. I presume sensor one is the one in the down-pipe?

3. Mixture - constantly swapping between rich and lean. Varying times stuck on one or t'other. I do have a modified 48mm alloy throttle body on him (with the restrictor removed and holes filled) - I wonder if I should stick a plastic one back on and retest?

Is there anything anywhere that shows what all the readings should actually be? It's great to be able to see them but if we don't have a reference point then all the great data isn't as useful.

Does your ECU support EOBD mode? Can you log in using EOBD mode and look at o2 sensor voltages in EOBD mode?

It should do as Adam has 2no. O2 sensors so it's Mems3. looking at my o2 sensors on Torque gives me wowing on both (as Adam describes it)

Hi Philip - yes it does log on with EOBD - I'll do it in the morning and post results.

OK so I haven't done much this week as I have had yet another cough and my mum went in to hospital (all ok now)... so yesterday I swapped my modified 48mm allot throttle body for a bog standard 48mm alloy one... and the hunting I've been getting is a LOT better.. slight wowing on and off. The engine still runs what I consider to be lumpy though on tickover despite me raising it to about 800 RPM.

I checked the error codes again and now have:

P0481 Cooling Fan 2 Control Circuit Malfunction
P0655 Engine Hot Lamp Output Control Circuit Malfunction
P1487 EGRCHK Solenoid Circuit Malfunction

The second cooling fan is fine as I don't have air-con, however the Solenoid one is new! I've erased them and will see what comes back. With the engine idling (slight wow up and down between 800 and 900 as far as i can tell)

The live data is now as follows:


So anyone know what's going on maybe? I changed the engine bay air temp sender and it still reads 139 degrees!

I am just about to free up Meg's alternator which is seized, bung some petrol in her and fire her up too... so I'll report back what I find there later!

OK some more info. He's been sat a good 15 minutes idling.. and all of a sudden hes hunting up and down from 850 or so to 1200 maybe... nothing done apart from idling.

Also here are the EOBD readings:

If it's hunting up to 1200 then the base idle is slightly too high. How far did you turn the idle screw? Turn it back half that amount.
Getting the base idle correct is not easy because the iacv and ecu are always trying to get it to 850-875. The IACV has to be on the 'correct step' for it to work. i.e you set the idle to 850, the car idles OK for a while then the ecu/iacv moves a step and the idle is wrong again.
It really is a case of little changes and leave it to sort itself out. If it's hunting down below 800 turn the screw in slightly, if it's hunting up, turn the screw out slightly. No more than a half a turn.

Cool - will give it a go David. It's certainly a million times better withe the standard throttle body.
I found the injector rail it originally had I think in the shed - with blue injectors - you think it's worth bunging that back on too as I can't remember what one I put on when I changed to the alloy inlet manifold!

Typically when I got Meg started she had no faults, and everything seemed just right on e
the scanner! That's after being stood for a year with maybe a few half hour tick-overs!

Nudged it down a tad on tickover and it is slightly better - will try again with another 1/4 turn tomorrow maybe. What 'step' should the IACV be on? Seems to be showing 0 step on mine on tickover.

What so we think about swapping the injectors over? Does it matter what colour the ones on it are? The ones I have in the shed are blue.

Also as can be seen in the reading above the engine bay temperature sender is still reading 139 degrees ads it the fuel temperature. As I said I swapped the air temp sender over from the F, and it works as it should when I pull it off - the fan comes on. So far haven't seen the fan actually come on of it's own accord though!

I can't remember which way it works but the different colour injectors have different flow rates with 160VVC on MEMS3 flow less than the 143VVC on MEMS2.

So finally got round to lowering the tickover a tad again. It is now between 850 and 875. I have no idea though what the readings for the stepper etc should be as although the pscan unit is brilliant (and so well supported by the maker), we don't have a 'reference point' for each vehicle so we can check if things are right.

Here are the results of today's readings once Felix was warmed up -
MEMS 3 Rover connection:


MEMS 3 BMW connection:


EOBD connection:


Error codes (cleared and come back):


Although he now runs without hunting (so far - a drive will tell for sure!), there is still a lumpiness about his tickover. For example I start Meg after months of her sitting on my drive and she is smooth as butter! There's like a hesitation that is apparent on the tickover with Felix, it's not really bad but it does make his engine shake and the exhaust rattle a bit.

So any help greatly appreciated as always.

I think it's a great tool as well Adam but would also like a reference table to know what the readings really mean. I've searched the net but can't find anything.

If anyone comes across something, hopefully they'll post it somewhere and we can all pick it up. Needed for all mems versions of course.