91cougarxr7

Ford Mid/full size Cars, 1984-87, 3.8 liter & 5.0 liter, central fuel injection (throttle body injections)

This early fuel injection system is comparatively complex and not well understood. A Ford EEC-IV scanner or dual trace digital oscilloscope is needed to check:

1) that the two oxygen sensors (3.8L only) are switching together and nearly equal in amplitude (the 5.0L has only one O2 sensor);
2) fuel control at idle, by forcing the mixture rich, then lean;
3) fuel control at light and medium loads.

The air injection system can switch upstream and downstream (of the oxygen sensor) for catalytic converter overheat protection. Air injection will switch to upstream at 30-45 seconds at idle, forcing the mixture rich. Ensure that air switches downstream as the throttle is opened. The air injection switching solenoids are located below the coolant overflow bottle and are subject to rust, dirt and corrosion.

This system is extremely sensitive to low manifold vacuum, a typical condition for an older vehicle at our altitude -- check timing chain, ignition timing, carbon buildup, exhaust back pressure and leaking EGR problems. Verify manifold absolute pressure frequency at or near 102 hz at idle. Fuel pressure is another critical area. It is not uncommon for these systems to be running at or near 45 psi. Ford specification is 37-40 psi; check and adjust to the low end of this specification at the throttle body as necessary. (Do not set below 37 psi!)





taken from http://www.aircarecolorado.com/repair/fixesfor.htm. its for emissions if you have them in ure state