Microtech and the Factory ECU

[s-twig]

Hi

In an effort to determine why my temp sensor is reading lower than it should, I was told to unplug my factory ECU (which is still connected in the presence of an Microtech LT8) and the engine should still run. I disconnected the factory ECU and the Microtech gets the correct temperature. However when I start the car the revs drop off and it stalls after ~5 seconds, or if I apply some throttle. I was wondering why this might be... could my LT8 be set up as fuel only (but would the car still start fine?)? I'm not sure, but as always I'm ready to take some advice.

Cheers

Stu

[TERRA Operative]

How come the Microtech ECU isn't operating as standalone?

[s-twig]

The previous owner had the Micotech set up... I'm trying to figure it all out. Just can't figure out why the car stalls when its only using the LT8.

[EldarO]

is it auto and the factory ecu is still needed to control box?

[s-twig]

Nah she's manual. It was suggested that because the Microtech is now reading the correct temperature it might not be giving it enough fuel to start. So once it was warmed up I disconnected the factory ECU and started it; it started but was idling around 500-800 rpm and there was a really strong fuel smell. So I'm not too sure. It idled longer than it did before but still stalled after maybe 20 seconds and when I gave it some throttle, it hesitated for approximately 1 second before the revs increased.

[oldcorollas]

is the fuel pump still on? or it just stays on for a short time then turns off when the stock ECU is not giving it signal? (ie, power to the fuel pump relay)

[s-twig]

I'm not sure, is there any easy way to tell? I would say it is on, the engine run longer when it was warm, probably about 20 seconds before stalling.

[CrUZida]

Yes, you are correct in your assumptions.

The cold start enrichment/temperature compensation table has been set up to correspond to the temp sensor readings while going to both computers (ie, the wrong reading).

When you unplug it from the old ecu it gets the correct temp but that part of the map is incorrectly set up.

What you need to do is change the temp correction map to be correct.
I'd suggest plugging the temp sensor back into the old ecu so that the car starts correctly, and then start it and follow how quickly the temp changes on the ecu.
Then map this out on paper and figure out how to set it up with the old ecu disconnected.

Then when you have it figured, just mod the map to suit the correct temps.

I realise the above is written very poorly, but if you know what I was getting at then you'll understand it...

[Roman]

Read this thread.

http://forums.toyspeed.org.nz/viewtopic.php?t=18333

[chris davey]

Just go to water temp compensation map and play with it as Cruz suggested. The microtech is so easy to tune it isn't funny

Also, do you still have ISCV and is stock ecu controlling that? If so, and you want to get rid of stock ecu all together you may need to crack the throttle open a little bit and make sure you recalibrate the TPS in microtech.