"Barry S." > wrote in message

> >> My 1990 acura integra did not pass Virginia emissions due to high CO2 at 25
> >> MPH. I think limit was 80 PPM and it tested at 140 PPM. It has news plugs,
> >> clean filters, and 173,000 miles.
> >> Is this a simple mixture adjustment? Thanks,
> >> Dan

> Based on the #s provided, I suspect there is some sort of fuel control
> problem.. HCs are elevated at 25, but fine at 15. CO is fine at 15
> MPH, but off the chart at 25 MPH.. So somewhere along the test, I
> think the car broke into open loop mode. (non-fuel-control) This is
> something you may want to send to a mechanic.

A faulty ECT would go into open loop mode on all rpm range. It
appears the OP pass the low speed test that indicates the ECT is
good. At higher cruising speeds the ECU will rely mostly on the
O2 sensors' response. If the close loop responses are bad it will
show up on the 25-mph readings.