90 Reatta idle surging after going into closed loop

[2seater]

I would need to go back over the saving from the crusher thread to confirm, but I think we wound up replacing the ECM because of O2 and open loop issues. The clue was notations in the history someone was keeping in the car that the O2 was changed multiple times making it likely they were chasing a problem of some kind.

[2seater]

I did look through that three year old thread and around page four or five, we did in fact change the ECM. The O2 sensor came to life and closed loop engaged. I cannot tell you if one or the other would cause it to stay open loop, but it did require a donor ECM to get everything to work properly. 

[drdelsol]

well,I have O2 sensor data again. Just got done replacing the ECM. 

Looked like it had been replaced before.  My wife said a couple weeks ago she had a feeling it was the computer. We will be married 36 years tomorrow so at least she finally gets her car back.  Its running perfect.

 

Thanks so much for all the help.

Edited June 20, 2023 by drdelsol

[Ronnie]

Thanks for following up and letting us know what fixed it!

[drdelsol]

Sigh.  Lasted one day. Now getting b334. Ac , speedomoter, tach not working . No e data. Ill start a new thread for this one sometime

[Ronnie]

41 minutes ago, drdelsol said:

Sigh.  Lasted one day. Now getting b334. Ac , speedomoter, tach not working . No e data. Ill start a new thread for this one sometime

Sorry to hear that. I've never heard of anyone getting that code. Below is the troubleshooting flow chart for an '89. I think it is probably the same as your '90. Maybe it's just a bad connection.  Hope it helps.

 

[Ohjai]

Ronnie posed the info for an 89, this is from the 91 manual.  Hope it helps.

 

 

[drdelsol]

I switched them a couple of times today. If i use the old computer I don' t get the B334 code but I also don't get the O2 sensor data and it dies. If I use the new,refurbished one, it runs but I get the B334 and no Rpm, speed, temp or ac. Did the connections several times and only get the E data loss with new computer so probably the new ECM and not the wiring. Guess I'll try another ECM

[2seater]

When mine did that last year, it was the Prom itself that had the issue. It was in a thread about the spare parts LN3  plus a supercharger. It had me chasing my tail, switching ECM's, switching Proms where it would settle down only to rear its ugliness again. The Prom itself had to be changed.

[Ronnie]

I split the discussion about coolant temperature off and put it in a new topic. Hope I didn't mess up this topic discussion by doing that.

[drdelsol]

Ok. Just put in the second reconditioned ECM from Rockauto. Everything works now. We have AC, all the dash works and great idle. Took it for a longer test drive this time and no problems. Going to try to send the first ECM back. 

Thanks for all the help. Really mean it.