98 2.5 5 speed ghost idle rising??
#1
98 2.5 5 speed ghost idle rising??
98 2.5 with 5 speed trans. every now and then (not all the time) my truck will raise the idle by itself without me touching the throttle, only after i am cruising and take it out of 5th gear or so to slow down or stop and throw it in neutral; the rpm's will stay at the cruising rpm (2000 or so) and then start to ride, i've seen 2500 or 3000. then when i stop it all the sudden drops to normal idle rpm. just started doin this yesterday so im not familiar with all the issues yet, just a little ackward. it's acting as though your starting the truck up and getting the initial high idle, except it isn't dropping back down, and sometimes it's going higher.
where do i start with this ghost idle?
where do i start with this ghost idle?
#2
Possible Idle Air Controller sticking but that should continue to hold RPM even after the truck comes to a stop.
More likely, it is a problem with the Throttle Position Sensor voltage. TPS voltage to the PCM typically drops to around 1 volt with the throttle closed. If it stays above 1.27V at closed throttle, the PCM will think it is in pre-position mode and keep the IAC at too high of a duty cycle.
EDIT: corrected voltage value.
More likely, it is a problem with the Throttle Position Sensor voltage. TPS voltage to the PCM typically drops to around 1 volt with the throttle closed. If it stays above 1.27V at closed throttle, the PCM will think it is in pre-position mode and keep the IAC at too high of a duty cycle.
EDIT: corrected voltage value.
Last edited by V8 Level II; 06-25-2012 at 07:24 PM.
#3
Possible Idle Air Controller sticking but that should continue to hold RPM even after the truck comes to a stop.
More likely, it is a problem with the Throttle Position Sensor voltage. TPS voltage to the PCM typically drops to around 1 volt with the throttle closed. If it stays above 1.53V at closed throttle, the PCM will think it is in pre-position mode and keep the IAC at too high of a duty cycle.
More likely, it is a problem with the Throttle Position Sensor voltage. TPS voltage to the PCM typically drops to around 1 volt with the throttle closed. If it stays above 1.53V at closed throttle, the PCM will think it is in pre-position mode and keep the IAC at too high of a duty cycle.
#6
What I would do:
- Verify that the throttle plate is closing fully.
- Measure TPS bn/wh to gy/rd with key on. Should be approximately 5V.
- Measure TPS gy/rd to chassis ground with key on. Should be approx 0V.
- Measure TPS gy/wh to gy/rd with key on. With throttle closed, should normally be approx 1V (acceptable range is 0.53~1.27V) Open and close the throttle a few times to be sure that the voltage returns to that range every time the throttle is fully closed.
Thread
Thread Starter
Forum
Replies
Last Post