Try running Chevron Techron concentrated fuel injector cleaner in a 1/4 tank of gas.
Also, may be the issue in this TSB.
A hard start or no start condition may occur when the engine is cold. The engine may not start without cycling the key to the OFF position and back to START. Ignition switch bounce (loss of electrical continuity between contacts) may cause the EDIS module to recycle several times or to lock-up and not allow a start at all.
Install a new ignition switch containing synthetic lubricant which reduces the amount of bounce. Also, install a new wiring connector containing a new material that is compatible with the new synthetic lubricant. Refer to the following procedure for service details.
- Disconnect the battery power.
- Remove the trim panel. Refer to the 1990-91 Ranger/Explorer Shop Manual, Section 11-04B, for removal procedure.
- Turn the lock cylinder to the RUN position.
- Remove the two (2) nuts on the ignition switch.
- Separate the connector from ignition switch by gently prying on the ears of the connector and pulling apart firmly.
- Disengage the terminals from the existing connector. Discard the connector.
- Insert terminal into proper locations in new connector (F2TZ-14489-A), Figure 1.
- Remove the spring clip from the new switch (F2TZ-11572-A). This clip keeps the switch in the correct position during shipment.
- Press the new connector (F2TZ-14489-A) onto the terminals of the ignition switch. Be sure the tabs lock securely.
- Locate the switch on the weld studs on the steering column.
THE END OF THE ACTUATOR ROD MUST FIT IN THE HOLE ON THE SLIDER.
- Install the nuts on the weld stud. Tighten to 4.45-7.24N-m (39-64 lb-in).
- Connect the battery terminal.
- Check the switch operation. If necessary, adjust it. Refer to the 1990-91 Aerostar, Explorer, Ranger Truck Shop Manual, Section 11-04B, for adjustment procedure.
- Install the trim panel.