RPM once again

[werewolf]

still working on my old 87 4x4 ranger 2.9v6. it's a five speed trans. Ok i put in a new rad. a new thermostat it is a 195 with the jiggle on it . replaced the ECT sensor, replaced the IAC sensor. replaced the MAP sensor. cleaned the TPS sensor. I have sprayed b-12 over the engine at idle, it don't give signs of a vac. leak . so i'm also not real sure the tack is right . but now it starts up most of the time on the first try. but the rpm's go to around 1400 for about 30 sec. and then drops to about 1100 and stays there till the temp gauge moves off the cold mark. then it drops to about 800, rpm's. i was reading in your tech articles that if don't come down to 600. has a vac. leak b-12 not showing to have one

 

[aspevacek]

Check the IAC out and make sure it is functioning. That or the throttle plate both act as a vacuum leak off the simple way they operate. The gap in the throttle plate allows regulated air into the motor and the IAC allows air to bypass that gap.

 

[monstermazda]

I never had luck with spraying for vacuum leaks but double check your vacuum lines or block all vacuum ports including break booster

Sent from my SAMSUNG-SM-G870A using Tapatalk

 

[enjr44]

Pull the connector off the IAC. Rpm should drop to 500 or less and may even die. If not, pull the IAC and watch its operation. Key off - completely closed, key in run - completely open (clean it while you have it off). It is a stepper motor with about a thousand different positions when the engine is running.

If all that is working correctly you have a vacuum leak or the throttle body stop screw has been played with to get the higher idle. The stop screw is there to keep the butterfly from hitting the sides of the body (not adjust idle).