Bake My ECM?

So after much gnashing of teeth I finally broke down and took the Subaru to a trusted mechanic to fix the persistent cylinder 1 misfire.  Diagnosis is the engine control module has gone bad.  New ECM is at least $730 plus labor, dealer has to program it to play nice.  Dealer is almost an hour away.  Earliest appointment leaves me nearly four weeks to find a cheaper solution.

Has Subaru had issues with bad ECMs?

What does the GRM hive-mind think about baking the computer?  The googles tells me oven temps anywhere from 320 to 390, for about 5-10 minutes, and to only bake the circuit board.  Can I disassemble the computer down to just a circuit board?

Is this too crazy to even contemplate?

Since you are relatively local to me I feel for your plight and tried to see what resources I can lend.

I do not have much Subaru experience and I do not know of any Subaru experts in the area.  I see you said appt is 4 weeks out.  For Subaru dealers near you there is (none, but):

SW: LaRiche in Findlay:  55 minutes

NW: Yark in Toledo: 1 hour

NE: Ganley West in N.Olmestead  1:15

E: Brunswick in Brunswick 1:30

Does this issue leave the Subaru undrivable/unreliable for 4 weeks?  If so, I have the resource of some spare vehicles that just sit here, mostly undriven, most of the time but fully ready to go.  Does the Subaru need to be towed?

The Sumo Wrestler, Montero Limited:  Great at domestic chores and kid hauling.  Has a tow rating of 5k# but U-haul will not rent you a car trailer (but will a tow dolly which will not work for Subaru) due to the fact that Uhaul only rents up to 80% of tow capacity.  

The Gov't Mule, Ford F250 single cab:  Less great at kid hauling but it does have the ability to turn off the front passenger airbag when hauling kids. My daughter loves riding in it!   The bench has enough room for two car seats.  It will haul anything you throw at it and Uhaul will rent you a full car trailer.  

You know where I'm at.  You know how to reach me.  

Happy to help.  

Baking a 70's motorcycle CDI units is common.  The capacitors absorb water vapor over time due to their paperboard construction.  Electronics aren't made the same way now but you never know... It the car old enough you can swap the ecU or does it need to have vin programed and addresses set for the other computers it talks too?

I would only try baking the ECM as a last-ditch hail-Mary tactic. It's best to do just the circuit board, you could melt plastics in the case. The primary goal of baking it is to melt the solder and effectively re-solder any broken solder joints. Might fix the problem, might damage it beyond repair...worth a shot if the only other thing you can do with the ECM is toss it in the trash.

Before baking at least look it over and see if you can ID the problem area. 

This works for Toyota transmission computers. I have first hand experience. 

Don't bake me bro!

Thanks for all your wisdom.  And especially John Welsh, thank you for your generous offer.

The car is currently drivable with a bad idle.  But it hasn't died and continues to start.  I don't drive many miles on it and I plan/hope to limp it along until the appointment.  Or until I figure out a better option.  The bike and trailer may see a few school runs as long as the weather holds.

However, if, rather than merely baking the ECM I >cook< it, or screw up the disassembly, or screw up the re-assembly, then I would be forced to tow it to the dealer.  I'm waiting to receive the full download of GRM wisdom before I decide.

Ganley Westside Subaru received a recommendation from the trusted mechanic, and were good to me when the car was in for the airbag recall.  (And they're giving me a free loaner!)

And I should have referenced my earlier thread on this misfire:

Does This Coil Look Bad?

A reliable rebuilder might be able to repair yours.  If they know the specific problem you are having, they can find the bad driver on the board and replace it with out screwing up the security programming. 

Is it a constant misfire?  No injector pulse, or no spark?  

What year is it? I actually wrote a thread about this very issue...

https://grassrootsmotorsports.com/forum/tech-tips/late-90s-to-early-00s-german-car-electronics-not-working-put-a-torch-it/125707/page1/

I used this torch..

https://www.harborfreight.com/butane-micro-torch-63170.html

You can more precisely pinpoint all the solder points and actually watch the solder reform.The German boards constantly saw, this type of micro-cracking saw

dealers/owners, chasing their tails trying to fix the problems.

Depending on the board, and the problem, your chances range anywhere from 'possible success' to 'kill it even further'. The thing is, this method will really only cure fractured solder joints. A genuinely failed component won't come back from the dead by reflowing the solder. 

Typically solder reflow profiles for lead solder peak around 250c for around a minute.   lead-free solder closer to 265c for a minute.   This is after a controlled pre-heat and soak for a 5-6 minutes at a lower temp nearer to 200c.  Then the kicker is if you cool it too fast you risk creating new stress fractures, heat it up too fast you risk insufficient solder reflow.  Baking to eliminate moisture is done with a very different time/temp profile (Usually 40-60C for about a week or two,  or 48 hours at 125c).  

And there is risk to it.   Some of the components may not survive reflow temperatures.  Lower temp rated parts are added later, if there are any, and they could melt/fail.  Connectors will be your biggest worry in this regard.  Moisture sensitive parts can potentially 'popcorn' on you, as the absorbed moisture flashes to steam.  

If things are limited to the #1 cylinder, then you can possibly isolate the section with that driver and reflow individual solder joints.  Knowing what the board looks like would help me identify where that may be.