Scottish Elises

Can anyone out there help, a couple of weeks ago had a a flat battery and attempted put my Land rover battery on the car and momentarily got the terminals the wrong way around (I know real schoolboy error).
After starting the car (battery correctly connected) the car would not run smoothly or idle, it was hunting between 500 and 3000 rpm. Got a friend to run a diagnostic and the fault was showing no voltage at the oxygen sensors of the CAT, both upstream and downstream showing zero volts.
After a lot of electrical checks and not finding any problems, seemed like an ECU problem (had I fried it with the battery cock up).
Sent the ECU away to the ECU Doctor and they said it was fine and working properly.
I put it back on the car yesterday and amazingly it was running as sweet as a nut again, No problems other that the engine management light showing a fault. Drove it my local garage, car running perfectly, asked if he could run a quick diagnostic to see why the enine managemnet light was on, with a view to switch it off.
First couple of tries the car was not communicating with his computer (he was trying it as a Rover) then his machine stopped working and would not power up.
After a couple of resets he was reluctant to try it again, I thank him anyway and start the car and then you've guessed it, the fault is back again and I limp home on what feels like 2 or cylinders.
First question, is there anyone in the Aberdeen area I could take it to, I use Ricky Gauld for servicing, but he doesn't have too much in the way of diagnostics etc. I have also been in contact with Ali in Edinburgh who has been very helpful but at a bit of a loss without seeing the car (obviously difficult as can't drive to him.
Second Question - Does anyone have any ideas what the problem might be?
Rob

Seems to be that the ECUs do not survive reversed polarity very well at all.

Mine did

It did blow the fuse that runs from the alternator to the starter ????

Which model have you got rob?

And do you have AA cover? (hear me out on this)

Is this an S1 or an S2?

If it's an S1 (in which case it must be a 111S as it has a MIL lamp) then I'd be looking at the misfire detection unit.

If it's an S2 then I'm pretty sure it will be the ECU, despite what ECU Doctor told you.

Dan

Unfortunately don't have AA cover, and it's an S2.
I agree with the thoughts on the ECU although why was it running perfectly when I got it back and up to the point where my local garage plugged his diagnostics into it.
Extra bit of info was after having a look again last night noticed the immobiliser light wasn't flashing, so checked the fuses and a 7.5 amp fuse had blown, it's the one for the battery services (although not too sure what that covers) anyway changed it started the car and it ran fine for a couple of minutes, until it started idling progressively quicker and then started hunting again.

Dan
Forgot to mention it's a 111s
Rob

Hi Rob,

I had the same problem before but was not caused by reversing polarity. If the car goes in limp mode and displays the MIL, the ECU detects some parameters are not correct. After trying a few pals, I eventually tried the AA to plug their computer into my car, and I can tell you that they can check a he'll of a lot more with their systems than most!
I have membership and more than willing to help, but I live in Stirling. My issue was the potentiometer which sends the throttle position to the ECU, Lotus thought I had a knackered Pin or a knackered lamda sensor and gave me months of runaround.
I told them what AA had said, but they just wouldn't take heid!

There is also an ECU reset which can be performed by compatible diagnostic machines (and the AA's) as a first try.

Stephen

Stephen
Thanks for the info, up until last year I had AA membership along with Parts and garage service cover too, so certainly wouldn't rule them out.
Strangely enough after leaving the battery off overnight and trying again today the problem seems to be sorting itself out.
Still getting some fault codes and the Engine management light on, however at least its now running as sweet as a nut again.
Rob

Whilst it's just me stabbing the dark, a full ECU reset sounds worthwhile, just to get back to a known state for any further diagnostics?

No problemo,

I got rid of the MIL 3 times in the past by filling the car up, and going for a good run - giving the engine a good workout and getting good heat into everything. This was a fun and fixed the light problem, hopefully it will work for you

Stephen