93 240 high idle

Any ideas?

Hello there!!, my 1993 245 is idling at 2,000 RPMs (big tach replaces the clock). Suspecting vacuum leaks checked the hose between the air sensor and the throttle, and the hoses to the Idle air control valve, and all check ok, measured resistance of the fuel temperature sensor (the dual sensor that sends engine temp to the ECU and to the ignition computer), both sensors measured the same, replaced, results are the same. Checked operation of throttle switch, checks ok, removed and cleaned throttle body (not too dirty), replaced gasket, still the same. Scanned for codes, no codes stored (1-1-1). Removed and cleaned Idle air control valve (not too dirty), idles still at 2,000 RPM. Disconnected the IAC, and the RPMs go down to about 1,000 RPM they used to be around 750 last summer. Gas mileage is bad too, I suspect it is running rich. Disconnected the Airflow sensor, The car idles really rough,(limp home mode), get codes and I have to give it gas to keep from stalling. put it back, clear the code, reconnect the IAC, idle is back at 2,000 RPMs. Any suggestions?

Thanks

Arnold

Make sure that the throttle switch clicks when you just open the throttle. Make sure the transmission throttle cable is not binding and preventing the throttke plate from closing correctly. Make sure the three nuts that hold the throttle housing to the intake manifold are tight and that the gasket is not leaking. Make sure the eight nuts that hold the manifold to the cylinder head are tight and that the intake manifold gasket is not leaking. Pull the front cover off the motor and ensure that the timing marks for the cam and crank are aligned correctly. Or, rap on the IAC with a hammer, if the idle drops to normal, replace it.

Bob