"Repaired" ECU drops 8-9 MPG
 

I had a coolant leak from the water pump and during the repair, the dealer noticed that the ECU was slightly out of spec. I was not clear at the time, but I think they made a "repair" by adding a resistor in parallel in the ECU (rather than replace it - which would have cost me ~$1,000!) - and now my FE has dropped from ~45mpg down to ~38mpg. :confused:

I have not seen mileage that low in 4+ years. I'm going to confirm that they did this, and ask if it can be reversed.

It is basically negating all my ecomods... :(

What you mean out of spec? Now it's using more gas so it will pass the mot test?
Or they made some other mistake, not related to ECU. Same as when i disassembe/assembe some device, sometimes i have an extra scre lying around :D

I first read you got increase in FE :D I'm going to try that increase by replacing current ECU with Megasquirt in my car in next year :)

The spec they wanted to fix had to do with a temperature threshold being a degree or so off. It was fine (other than a leaking water pump).

It doesn't appear that you've run through a tank yet. It might just be that your SG calibration is off.

if they did anything to the ecu, it will need to relearn your driving habits before you see optimum FE.

Sometimes they will "flash" the ECU to the newest calibrations without telling you. Typically the newest calibrations decrease mpg in an effort to fix all of the "problems".

Is this a Scion? Its my experience if you change anything to disconnect the battery for 15 minutes, then connect, start it and leave it idling for a half hour so it relearns everything.

Sounds kind of odd a national car dealer would go through the trouble to add a resistor vs just replace the whole ecu. :eek:

The new ECU would have cost me ~$1,000, so no thanks. I'll keep you posted.

My first thought was, perhaps a sensor didn't get hooked up again and it's never going into closed loop... don't know what they did though.

What symptoms were present with the "slightly out of spec computer". If there was no check engine light or codes present, I think it is crap, frankly.
What was the justification for the "repair".
Federal emissions law requires them to replace a defective ECU for 8 years and 80k miles.
regards
Mech

I've owned the xA for ~6 years and 7 months - but it has ~139,000 miles on it.

Was the repair something due to a complaint or something they decided to do on their own?

Out of spec means it's not using enough fuel. Gotta get it back down to EPA, that's the plan.

I'm with the "ECU needs to relearn" crowd. Here's hoping that your mileage returns!

We'll see how it goes. The odometer is indicating a little over 200 miles at the half full mark, where I have been getting ~240-250 miles. I had an unusual couple of days of driving right at the beginning of the tank -- short drives just within the very small town I live in. Since then I have resumed more typical drives; and I have now eeked the SG II up to 39.2mpg.

I hope the ECU "learns" quickly?

I looked on ebay, seems ecus run from 75 bucks to about 150. Have you gone back to the dealer? Have you called your bank to dispute the charges?

I had an xa for 30 thousand miles, got 37 mpg worse, mid 40s best. It liked to cruse at 40 mph in 4th gear. :turtle:

I'll see how this tank goes (I've got it up to 40MPG!) and then ask if the "fix" is reversible.

I do not know if the ECU made by them is slow but a car should only take at most half a tank to relearn most likely less if it was reset (disconnect battery). The 93 Bonneville's only took half a tank to fully learn, the 98, 2000 and 2002 if I reset them (I did it with a tuner) could relearn in 50-100mi.

That issue would most likely be a temp sensor was off and should have been replaced to correct the issue. If it was a turn on/off point that the ECU uses and the sensor was working correctly then they should have flashed the update or reflashed the current version of the ECUs tune.

The MPG's are climbing - 41.3 now, and because the tank started so badly (<38) that means I am doing pretty well. The ECM does seem to be "learning". Also, I am getting brand new set of Nokian Hakka R's tomorrow, so this tank will be an outlier for several reasons.