Thread: choke adjustment 3.9 efi

Try cleaning the stepper and its ports, set the TPS correctly (300mV + or - 20) and clean the throttle body, Throttle plate airgap should be .05mm. Set the airflow meter to 1V and replace the thermostat. Timing should be at least 6 degrees, preferrably 10.

This is for starters.

The procedures are all in the 'good oil' section AFAIR.


(I know some of what I have mentioned is for flapper EFI type, but I have used these for Hotwire systems too, especially 'tired' engines and improvements can be made by doing these things IME)


JC

Originally Posted by justinc

Try cleaning the stepper and its ports, set the TPS correctly (300mV + or - 20) and clean the throttle body, Throttle plate airgap should be .05mm. Set the airflow meter to 1V and replace the thermostat. Timing should be at least 6 degrees, preferrably 10.

This is for starters.

The procedures are all in the 'good oil' section AFAIR.


(I know some of what I have mentioned is for flapper EFI type, but I have used these for Hotwire systems too, especially 'tired' engines and improvements can be made by doing these things IME)


JC

thanks, mine is the 5am hotwire i had replaced the stepper motor a couple of months ago and never been right since, i will looks at the other setting too on the weekend

robbie

when i start the 92 rrc in the early mornings it revs at around 1500 - 2000 but if i switch her off then start her up again it revs back to normal at 500 - 1000 (this is at park position both times) even if i drove for 15mins or longer it still reves high and dosent drop automaticly.
just wanting to know if i can adjust the choke or if its a faulty stepper motor or something

If I were you I would be replacing the thermostat, as this is a symptom of slow warm up. The stepper speed at cold start is controlled by the ECU temperature sensor and the idle will stay up if the temp sensor reads over a certain value.
Or alternatively the ECU temp sensor could be faulty or have a poor connection.
What is the temperature gauge saying during this? Is it staying down low or rising to just below centre? If down low-thermostat, if normal look at the ECU temperature sensor.

I don't know why it would idle properly after a second start, except that if you left it a while, heat soak may increse the temprature at the ECU sensor position enough to make the resistance of the ECU sensor below (warmer) than the cutoff for fast idle.

Regards Philip A
Regards Philip A

Hi Philip,
When you mention 6 possibly 10 degrees, I have a 3.5 efi, are these numbers the same? I'm also assuming you mean BTDC and not ATDC, the manual talks about both before and after timing settings. dependant on the dizzy number.