Hi Everyone,

1990 740T, 205k miles, auto. ipd sway bars, draw-tite trailer hitch.

The car has a new exhaust system, it is true dual downstream of the downpipe. All of the exhaust runs through one of two catalytic converters. Both converters seem serviceable, get warm and are likely working. I did the planning and installation myself with two generic converters of the type sold at fleet farm and auto zone and listed in their books as replacements for the Volvo factory converter. The original factory converter is long since gone, I took it to the city metals recycling bin several years ago, after ignorantly assuming that it was at the end of its service life, and changed over to the first of the two inexpensive aftermarket converters noted above.

Engine starts and runs fine. With the dual exhaust, the car also returned 27 mpg over its first 110 highway miles a couple of days ago with the new exhaust. Midrange acceleration, such as used when entering the freeway or passing, is still surprisingly weak. It is passable, but clearly weak. This may be crucial because I wish to tow a small keel sailboat cross country with the car in the near future. Boat and trailer weigh close to 3,500 lbs. Cylinder compression seems to be running about 130 psi per cylinder. This is down from 158-160 psi about 75,000 mi. ago. I can repeat this test if indicated.

The car has no IAC valve. The connector is securely taped shut and the air passages are too. I adjusted the butterfly in the throttle body to allow for a little air when starting and idling the engine. Works. Been working this way since last summer.

But is it possible that the absent IAC motor and attendant signal may be misleading or confusing the ECU? Maybe I am not getting optimal motor management without the IAC in place? Could that be the cause of the weak midrange acceleration? I will acquire and install a new or rebuilt IAC motor right away if indicated. But I would like comments from the Brickboard first. Thanks everyone.