Issue with ECU swap

[55rag]

Hello All, I have an 87 325is that came with a 153 ECU. I am planning on upgrading to a Turner chip and figure I may as well put in a 173 ECU for the code option. I bought a 173 ECU off ebay and installed it today to test it out. The car idled and drove fine before but now has a stumble off idle. I didn't get a chance to take it out for a test drive and I'm wondering if the new ECU has to have time to read all the sensors?

Also, I did the stomp test by pumping the accelorator 5 times with the ignition on but I don't get the check light flashing. My check light is normally on anyway due to my front turn signals being jacked up but I don';t get any flashing. Is it possible this is a bad 173 ECU?

Thank you

[finnmole]

How long did you drive the car with new ECU so far?
It takes some time for the ECU to learn and adjust...i ordered a Turner chip as well (out of stock now due to chip shortage) and read in the instructions somewhere.
You need to idle the car for 10 minutes, then turn it off..then drive around at different speeds etc so it can adjust.
I'm guessing it's the same for a new ECU (depending what car it came from).

The stomp test may not work on that version of ECU as I had a 173 in my 88 325iS that i couldn't get to work no matter how many times i tried.
I then bought a new one off ebay and it had a slightly higher serial number and the stomp test worked right away.

I'm assuming your TPS switch is working? The stomp test needs that to work.

[55rag]

Thanks Finnmole, I haven't had a chance to drive it yet with the "new" ECU. I'll be doing that tomorrow. If the ECU I got doesn't support the stomp test then it's all a mute point because that's the reason I bought it. I'll either have to try my luck on another or just go back to the 153.

I think my TPS is working just because the car started and ran good before I started messing with it.

Thanks for the good information.

[finnmole]

You should test the TPS...three pins; ground in the middle...you should get a short to middle when throttle is closed, start opening the throttle it goes open...should get a short on the other side to middle at WOT.
Two pins at the ECU are waiting for the ground when you pump the gas to start the flashing lights.

My TPS was gummed up and didn't short out at WOT which made it less quick when stomping the gas while driving (and the stomp test stopped working)