Well, not only did the world not end today .. but I can finally report that 5 months after starting this thread, my problem is now resolved. As I indicated earlier, the problem started as a TCS 3-1 indication (along with solid CEL) but was intermittant at first which hampered problem resolution. A couple of months in, it finally became a solid failure with no blinking codes for either the TCS or CEL which basically indicates a failure in the TCS, the CEL, or the wiring harness between them. Using the shop manual diagnostic routines .. and the fact that the TCS lights had come on first, I decided to focus on the TCS. After pulling it out and opening it up, it appeared that 4 electrolytic capacitors on the circuit board had bulged, which is similar to the problems that often occur with the BOSE amps. I viewed this as a good sign and confirmation that the TCS was probably bad (the ECU, on the other hand, has very few capacitors) and after consulting with BrianK, he agreed. So, I bought some new ones locally and replaced the bulged ones. Unfortunately, there was no change in symptoms. So, I figured maybe my soldering job was defective and decided to grab a used one off eBay (note - $Cdn for new TCS is about $2000). More delay waiting for the part .. no improvement. This prompted this thread:
http://www.nsxprime.com/forum/showthread.php/165087-How-to-disable-TCS-from-affecting-ECU
So, now I'm thinking it's either the wiring harness or the ECU. I had already done some of the easier wiring checks but some of them require that you use a special Acura harness that goes between the ECU and OEM harness and allows you to test individual wires with the ECU powered up. But, back in 2008, I had sent my ECU module to Prospeed and had them remove the OEM chip and install one of their chips, so based on nsxbuilder's response above, I figured that I should probably go back to my OEM chip to see if anything would change. More delay as I searched for it. Then I discovered that Prospeed had changed the ROM socket and I couldn't figure out how to get their chip out of the socket. More delays as I tried to contact Prospeed to answer some questions .. but never heard back. Eventually figured it out myself .. swapped chips .. no change in the problem.
Early in the problem, there was some urgency because I had planned to go to NSXPO in Denver but didn't want to drive that far with a CEL on and indications (1400 rpm idle) that maybe I was running rich. When my TCS fixes didn't work, I had to bail on NSXPO and the urgency dropped off because the car was still drivable. But with the failure of ECU ROM swap .. and the arrival of winter here in Canada, I was getting concerned with the car's habit of going to 2500 rpm idle shortly after startup and before the oil had gotten to where it needed to be. So, I took it back to the Acura dealer to see if they would come up with anything different than me. $300 later, the best they could do was recommend I get a new ECU. Canadian price would be $1800 and I'd probably have to wait until mid January for the part. Thanks to Delray Acura, I was able to get a brand new Acura ECU to my house for under $900 in 13 days. Plugged it in this morning (it was -20 and the four harness plugs were more than a little stiff) and everything is back to normal .. TCS and ECU lights are off .. car idles normally .. xmas came early.
Total cost for used TCS; new ECU; Acura testing labour .. was probably around $2000 .. but, hey, it's a '91 so maybe I should consider this as 'preventative maintenance' .. the TCS caps were clearly showing signs of early failure. I've had a look at the ECS module and there's only 2 electrolytic caps on the board and both are visibly ok with no bulges or leaking. Nothing else on the board looks unusual. Was it something tied to Prospeed's re-socketing of the ROM? Who knows? Was it tied to the fact that I drive the car in the winter at low temps? Sorry, can't answer that one either. However, my situation may have been the 'canary in the coal mine' early warning that for others whose cars are close to 20 years old and/or drive them at cold temps, you may be facing an ECU replacement in the future.
Just my $0.02 worth .. just wanted to close the loop on the thread
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