ECM Relearning....How long should this take?!

[coolwind57]

I'm day three driving my MJ since getting her back together.  This morning, the engine died 3 freakin' times as I performed a bunch of slow stop and goes, droving through my wife's huge work parking lot.  it often dies, usually when I come to a complete stop.  I figured my ECM just needs to relearn how to best operate the engine.

 

If I am correct on an ECM relearn, then how long does this usually take before she figures out not to shut down when rpms suddenly drop?  Am I being impatient or do I need to do something other than wait?

[90BlackMJ]

The Renix system does not "relearn" as it does not store any information. At every crank it gathers its info to run. May want to check out your TPS and or the IAC. 

[Ωhm]

IIRC learned closed throttle and fuel trim values are stored for next start up.

[cruiser54]

9 hours ago, Ωhm said:

IIRC learned closed throttle and fuel trim values are stored for next start up.

Possibly stores MAP reading also.

 

But, it isn't relearning now. Something else is wrong. 

[coolwind57]

I'll start by checking vacuum lines around the air box, which is the only area I worked on under the hood during my refurbishing these last few weeks.  Hopefully something obvious. 

 

I've never removed and cleaned my IAC, so that'll be a weekend task to complete.  The engine  now has 101K, so I doubt if any throttle area cleaning has ever been done.  If I have time, I may just pull the entire throttle body and give her a good cleaning.  Being a "cherry", I've never tackled a Renix TPS adjustment.  This  might be an interesting weekend.

[Pete M]

be extra extra careful when dealing with the sensor screws and bolts around the throttle body. they like to fuse themselves in place and strip the heads if you aren't putting enough pressure into the driver.     

[Ωhm]

When you get the throttle body off, do/check cruiser tip 14 – Restoring Throttle Butterfly Adjustment

[FrankTheDog]

I know on my 92 when my speedo wasn’t working it would die at stops. 92 is all electric speedo renix is mechanical speedo with an electrical sending unit and mechanical drive on the tcase.

Try replacing sending unit on tcase.

[DirtyComanche]

7 hours ago, FrankTheDog said:

I know on my 92 when my speedo wasn’t working it would die at stops. 92 is all electric speedo renix is mechanical speedo with an electrical sending unit and mechanical drive on the tcase.

Try replacing sending unit on tcase.

 

Renix speedo is an entirely mechanical cable drive and no information for the purposes of operating the engine or transmission is gathered from it.

[josehuerta]

Any advantage  to having my original ecu rebuilt versus just exchange for another? Any recommendations for a shop that rebuilds them (quality work, warranty, etc.)?

[josehuerta]

Not hijacking the thread but would like to avoid this kind of problem if possible. Mine is '91 so not renix -

[HOrnbrod]

1 hour ago, josehuerta said:

Not hijacking the thread but would like to avoid this kind of problem if possible. Mine is '91 so not renix -

 

What kind of problem are you trying to avoid? The HO ECU learning process? Would be best to start another thread detailing your question(s).

[DirtyComanche]

5 hours ago, josehuerta said:

Any advantage  to having my original ecu rebuilt versus just exchange for another? Any recommendations for a shop that rebuilds them (quality work, warranty, etc.)?

 

Is it actually dead?

 

Most of them are pretty rock solid...

[ParadiseMJ]

The Renix ECU is a pretty simple affair...but "rebuilding" it, for me, would be folly.  If you really think your ECU is what is causing your problem, swap it out with another from a junkyard. 

 

Barring that, I'd get out a DVM and start checking circuits that affect fuel, spark, the coil, your grounds etc.  In my experience it's pretty dang scarce that the ECU is the actual problem.

[josehuerta]

Apologies. My questions have detoured Coolwind's thread so I've started another. I thought I was headed where he is regarding the repair but the consensus is that it's unlikely to be a problem with the ECU in any case. You've given me good advice and everyone's input is much appreciated -

[coolwind57]

I had limited time to work on the problem this weekend, but I am relieved and excited to have found the solution in the one thing I was able to do.  

 

The problem seemed to be a dirty IAC.  Cleaned the heck out of it with thinner and swabbed interior mount of the throttle body, slapped her back together and no more hesitation and engine dying.  Seems to have smoother idle too, but this could just be my hyper-thrilled mind.    

 

Thanks for the input.  Once again, this place in invaluable.