Very high idle with DIY-EFI ECU

Technical Area Engine, Transmission, Exhaust etc
1

I have just installed a DIY-EFI PNP ECU onto my nb2 and as the title says I’m getting an idle of around 2000 revs on startup that creeps up to around 3000 after a few seconds, it also smells very fuelly.

I’m running a map sensor that I tee’ed off from the evap line and an inbuilt wb o2 sensor that are both accounted for in tuner studio, the ECU also came with a pre installed base map.

The car was idling perfectly on the stock ECU with no vac leaks. The only thing I’m thinking it could be, which I’m going to have a look at after work, is that on the first start I forgot to disconnect the maf sensor so maybe that messed with the fueling or something?

I’m new to tuning so any advice will be really appreciated :+1:

2

Was it a base map for the correct engine? Nb2 not nb1. Ensure all of your ecu inputs are set correctly. Things like injector size, temp sensor calibration, TPS calibration. That sort of thing.

3

Your MAP sensor should be taking a reading from a dedicated vacuum nipple on the intake plenum.

4

It was ordered from their website specifically for the nb2 and I’ve checked all the inputs even though they were done for me with the base map, only one I had to change was the iat sensor which just needed calibrating. And are you talking about the vacuum nipple that comes out just above the fuel rail directly behind the throttle body?

5

Any vacuum nipple that is not used for anything else will do.

6

Got ya I’ll try that later on, is there any other bits I should check over if that isn’t the case? Other than double checking all my inputs?

7

You probably need to check the settings for the idle valve. If the settings for the idle valve aren’t right it might be partially open…or the idle valve may not even be hooked up. Their website gives about zero information on what all circuits and features are enabled

8

If you can upload the datalog and the msq files will help to check

9

Yea looks like I have a vacuum leak as when I turn the engine off I can hear an evident hissing. I also took it for a drive to get it warm and it was idling from like 900-1400 with a duty cycle of 3%

10

But I definitely need to mess with the iacv settings after fixing the leak. It’s just weird that I could barely notice the leak when I had the stock ECU on

11

Take some soapy water in a spray bottle and spray around every vacuum hose and connection. Unlike a boost leak, instead of bubbles the soapy water will lower/smooth the idle as it temporarily blocks the airflow for a couple seconds

12

Great thanks for the advice I’ll give it a go when I have the time, if not a friend of mine has a smoke tester I can use on the weekend :grin: