Block Learn #'s ??

[JOHN07]

Can anyone tell me what their Block Learn numbers are? Normal is said to be 128. I get 119-121. Is this normal for an 87'Riviera? What would cause the numbers to be low? I have rebuilt the motor and have bored this motor .030 over and would have thought the numbers would be higher.

Also does this make sense:

1) No vacuum leaks because block learn would be above 128.

2) Fuel pressure is more than adequate with a low block learn value.

3) Clogged air filter or low compression equals low block learn numbers.

Any other thoughts?

Thanks alot Guys

JohnT

[Coop]

The integrator value is more like your instant air fuel ratio correction and the BLM is more like your long term fuel trim in an OBD2 car. Over time the BLM will update to try and keep the integrator at 128. Either way a number like 119-121 wouldn't have me concerned at all, ECM's just doing it's job imo.

[2seater]

Too much EGR flow can cause the BLM to go low also. I believe yours is vacuum operated. If the fuel pressure is slightly high, it will need to lean out a little to compensate. Maybe a slightly leaking injector? The number isn't really that low to start with, it has a much larger range of operation and you aren't close to the limits. If the integrator is bouncing around 128 everything should be fine. The BLM isn't a single value either, it is stored in different cells the ECM reads based on rpm and throttle position, so it will likely be different at different throttle positions and the load the engine is under. It is a constantly moving target, and conditions are rarely ideal. It is a good idea to take a look at the readings once in a while, just as you have, to see if there s a trend and possibly shortstop a problem. If it runs normally and mileage is what you expect, it sounds like normal operation.