91 740 B230FT. The sordid tale begins w/ a failed emissions test, high HC @ idle.
I swapped ECU (rebuilt Programma 1 yr old)for a junkyard one. Passed test.
Later, lamda trim error code lean/rich. High idle. Fix intake & exhaust leak. New FI temp sensor. Confirmed reads resistance it should (matches table in Volvo Green book 700/900, 1989-(TP32043/1).
Rough idle, still too high 1000+ rpm. Running rich. Tailpipe black.
O2 sensor works, squeeze fuel return line test, O2 reacts.
Without squeeze test O2 reads 500mv ish steady. IAC new & works.
Get Programma ECU back, install, O2 does proper sweep. Next day same thing, rich, rough idle, O2 500mv steady (squeeze test OK).
Fuel pressure 40 psi. Fuel volume OK at part & full throttle, will rev up & hold speed. Slight stumble if you mash the pedal.
AMM tested as far as can OK depending on Bosch manual or Volvo. See below for more.
Swapped rebuilt ECU from ECU Doctors in place of Programma. This one has a new style hybrid circuit installed. O2 test, .1-.9VDC sweep as normal. Idle good & smooth. On startup revs up a bit then falls to 750ish RPM.
A couple of days later same crappy idle, running rich, 113, 231, 232 error codes.
Swap AMM for one I pulled from my 91 940 B230FT. This one had worked fine except for intermitant power loss (like 2 plug wires were pulled).
Now smoother idle but hunts 500-900 rpm. O2 check erratic, .1VDC to.8 to .5 jumping around.

AMM test from Green book (above) says # 3 terminal w/ car running should be about 2.3 VDC, I get 2.39 VDC. FAQ says Bosch book for 280 212 016 AMM (mine)is 1.4 volts.

It seems like something is killing my ECU's or bad AMM's. Fresh out of both.


My questions;

1. Which AMM voltage is right 1.4 or 2.3?
2. Is there something I should check to see if a wrong voltage/signal is damaging my ECU's? New Bosch cap & rotor, bougicord wires 4 yrs old, all good resistance. No welding on car.
3. The car has run so rich that the CAT is probably sooted right up. Can this cause the craziness I see?

Thanks ian