Sorry for the long story but its the only way I can explain everything. The car is a 90 CRX SI with JDM b16 and PR3 ecu.

I was getting code 3 - map sensor every few weeks (5 weeks or so). At first it was simple, it would come on and I'd reset the ecu and drive away. Then it started happening more frequently (every couple weeks 3 or so). It was also getting harder to clear the code, reset the ecu 3 or 4 times. Then it started happening every week to the point the car was undriveable.

I replaced the map sensor, code came back. I replaced all the vacuum lines, code came back. I measured the voltage on the map sensor seemed ok (5 volts). I measured the output voltage from the ecu and it was reading 7.5 volts. So replaced with a good ecu and the car seemed to run fine. I bought a PR3 ecu and waited for it. Put the new ecu in last night and the car seemed fine, this morning code 3.

I'm baffled and the car is undriveable in this state. HELP.

 

I can't edit my post, so i'll add to it.

This morning the car was idling fine 1000rpm. Then the idle started to drop and was surging down to 500 and up to 1000. Then the car stalled. I tried to restart it but it just died again. I had to restart it and keep my foot on the gas to keep it at 1500rpm in order to keep it running.

 

https://honda-tech.com/zerothread?id=1353547

you have to test it at different amounts of vacuum to be sure its reading correctly all across its range.

also, have you checked for vaccuum leaks? Lumpy idle sometimes means a vaccuum leak.

edit: I'm sure you would have mentioned it, but have you had any other codes in the past few months?

 

I replaced all the vacuum hoses with brand new hose.

 

when i say vacuum leaks I'm talking about leaks around any gasket, like the throttle body-to-intake manifold mating surface or the intake manifold-to-head mounting surface..

check for leaks by running the car and spraying starter fluid on all the mating surfaces. When you spray on a leak the starter fluid will be pulled in and cause the motor to act funny.

 

thanks, that was going to be my next step tonight.

I've also found some info about field vtec controller. I forgot about it because its never on. So i think i'll remove it and solder/shrink tube any connections that were there.

http://d-series.org/forums/showthread.php?p=122427