almost stalls when stopping
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Joined: Jan 2006
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almost stalls when stopping
While in park the engine idles properly with just over 1000 rpm but after engaging in drive the rpm's decrease to under 1000 rpms and sounds as if misfiring but doesn't stall.
I changed spark plugs, spark plug wires and today I changed the upstream and down stream pressure hoses. Symptom persists, any suggestions?
I changed spark plugs, spark plug wires and today I changed the upstream and down stream pressure hoses. Symptom persists, any suggestions?
Hotshot
Joined: Dec 2003
Posts: 18,423
Likes: 9
From: iowa
more info needed like year and motor. 1000rpms is actually pretty high for an idle rpm.
Assuming no codes, and making some other assumptions you might have a sticky, dirty IAC possibly remove it and clean it with intake carb cleaner and reinstall to see if it cures the dropping idle.
Assuming no codes, and making some other assumptions you might have a sticky, dirty IAC possibly remove it and clean it with intake carb cleaner and reinstall to see if it cures the dropping idle.
Moderator
Joined: Jan 2004
Posts: 13,851
Likes: 111
From: SW Va
Faulty TPS (Thtottle Position Sensor) maybe, it tells the computer what postion the throttle is in.
It gets a 5 volt reference signal from the computer, so check for that.
With the throttle closed, you should be reading 0.5-1.0 volts DC at idle on the signal lead & 4-5 volts DC at WOT (Wide Open Throttle)
You can aso disconnect the TPS electrical connector & check it's resistance for proper range & smoothness of change as you go from closed, to WOT. It should read 3-4K ohms at closed throttle & change smoothly to about 350 ohms at WOT.
A analog multimeter, rather than digitial, is easier to use for this test.
On the IAC, (Idle Air Control) it bleeds contolled bypass air around the throttle plate to control idle speed.
With it's elctrical connector removed, it should read between 6-10 ohms, with the meters + positive lead to the VPWR pin & the - negative lead on the IAC pin. You may get lower readings if your leads are reversed, due to a diode in the solenoid windings.
At KOEO (Key On Engine Off) check the IAC's electrical connector for a reference voltage of at least 10.5 volts DC, between the VPWR pin & a good ground.
If you decide to clean the IAC I'd maybe try throttle body cleaner, as the rubber diaphragm is sensitive to some solvents, so don't use something like brake cleaner!!!!
Be aware some have limited lasting success in cleaning the IAC, maybe it's due to the type of solvents they use to clean it. So if cleaning it helps, be aware it may not last!!!!
On Edit: I forgot to say if you don't have a trouble light, & all the above comes to naught, try removing & cleaning the throttle body. Deposits may be preventing it from fully closing & upsetting the idle calibration.
Just some additional thoughts for consideration.
It gets a 5 volt reference signal from the computer, so check for that.
With the throttle closed, you should be reading 0.5-1.0 volts DC at idle on the signal lead & 4-5 volts DC at WOT (Wide Open Throttle)
You can aso disconnect the TPS electrical connector & check it's resistance for proper range & smoothness of change as you go from closed, to WOT. It should read 3-4K ohms at closed throttle & change smoothly to about 350 ohms at WOT.
A analog multimeter, rather than digitial, is easier to use for this test.
On the IAC, (Idle Air Control) it bleeds contolled bypass air around the throttle plate to control idle speed.
With it's elctrical connector removed, it should read between 6-10 ohms, with the meters + positive lead to the VPWR pin & the - negative lead on the IAC pin. You may get lower readings if your leads are reversed, due to a diode in the solenoid windings.
At KOEO (Key On Engine Off) check the IAC's electrical connector for a reference voltage of at least 10.5 volts DC, between the VPWR pin & a good ground.
If you decide to clean the IAC I'd maybe try throttle body cleaner, as the rubber diaphragm is sensitive to some solvents, so don't use something like brake cleaner!!!!
Be aware some have limited lasting success in cleaning the IAC, maybe it's due to the type of solvents they use to clean it. So if cleaning it helps, be aware it may not last!!!!
On Edit: I forgot to say if you don't have a trouble light, & all the above comes to naught, try removing & cleaning the throttle body. Deposits may be preventing it from fully closing & upsetting the idle calibration.
Just some additional thoughts for consideration.
Last edited by pawpaw; Sep 24, 2006 at 08:25 AM. Reason: add omitted troubleshoot info
