Unofficial Idle Adjustment (may only work on pre-March '90 cars)
(Bernie Benz) This procedure sets the idle speed to minimize the effects of sudden engine braking when the throttle is slammed shut.
- With engine at operating temperature, disconnect the ISV electrical connector.
- Adjust the idle speed with the throttle valve air bypass adjustment screw to 700 to 750 RPM. (This is just below the speed at which the ECU computer will control idle.) This sets a minimum idle speed well above zero.
- Reconnect the ISV elec. connector, and check the idle speed. The computer should control idle at 800 to 900 RPM. If it's faster, the ISV is not accurately following computer control, the sign of a sticky valve.
Warning: Bentley says the idle and CO content are interrelated, and must be adjusted together. The following procedures may be good for fine adjustment; however, they may cause more problems than they fix.
Pre March 1990 production date
- Clamp crankcase ventilation hose behind fuel pressure regulator, then remove oil dipstick and cover tube with a lint-free rag to prevent oil spray. (This step is probably more important for the CO adjustment rather than idle adjustment, so can probably be skipped.)
- Under driver's side glove/map compartment (near steering column) you should find two diagnostic connectors, with two jacks on each one. Bridge/short the lower jack between each connector (A1 and B1).
- Start car, turn off all accessories, make sure car is warm but radiator fan is not running, check idle speed. Should be 800 RPM +/ 50
- Adjust idle speed to spec at adjusting screw on throttle body (accel.cable is sticking out of it, adj. screw is pointing approx.to the air cleaner).
- Remove rear electrical connector from carbon canister shutoff valve.
- With engine idling and all accessories off, install spare fuse in the top of the fuel pump relay.
- Adjust idle speed to spec at adjusting screw on throttle body (accel.cable is sticking out of it, adj. screw is pointing approx.to the air cleaner).
