97 Grand 4.0 Low Idle Speed No Stall Help
02-28-2013, 03:30 PM
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Year: 1997
Model: Cherokee
Engine: 4.0
97 Grand 4.0 Low Idle Speed No Stall Help
97 Grand 4.0 Low idle speed of 400 - 500 rpm started this morning
IAC and TB have been cleaned (seemed to improve fuel mileage)
Tested TPS with multimeter and appears to be in spec from closed to WOT no sudden drops or spikes. .2 v closed 3.7V WOT
PCM was replaced few weeks ago
No stalling, hesitations, back firing etc.
Filled tank and added STP fuel system treatment a few hours ago
Reset PCM and afterwards the idle was at 800 - 900 for first 5 minutes or so (guessing open loop) then dropped back to 450-475
Checked for Vac leakes via visual inspection but found nothing
The distributor does have bad bushings which will be replaced this weekend. Not sure if this has anything to do with low idle speed as have known about bushings for a few weeks while doing cap, rotor, plugs, wires change and did not have low idle issue at that time.
Is there a way to test MAP sensor or IAC to verfiy proper operation?
Any ideas?
Thank you
IAC and TB have been cleaned (seemed to improve fuel mileage)
Tested TPS with multimeter and appears to be in spec from closed to WOT no sudden drops or spikes. .2 v closed 3.7V WOT
PCM was replaced few weeks ago
No stalling, hesitations, back firing etc.
Filled tank and added STP fuel system treatment a few hours ago
Reset PCM and afterwards the idle was at 800 - 900 for first 5 minutes or so (guessing open loop) then dropped back to 450-475
Checked for Vac leakes via visual inspection but found nothing
The distributor does have bad bushings which will be replaced this weekend. Not sure if this has anything to do with low idle speed as have known about bushings for a few weeks while doing cap, rotor, plugs, wires change and did not have low idle issue at that time.
Is there a way to test MAP sensor or IAC to verfiy proper operation?
Any ideas?
Thank you
03-01-2013, 06:45 AM
#2
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Join Date: Jan 2013
Location: Indiana
Posts: 47
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Year: 1997
Model: Cherokee
Engine: 4.0
IAC
Replaced IAC and all is good. 
97 Grand 4.0 Low idle speed of 400 - 500 rpm started this morning
IAC and TB have been cleaned (seemed to improve fuel mileage)
Tested TPS with multimeter and appears to be in spec from closed to WOT no sudden drops or spikes. .2 v closed 3.7V WOT
PCM was replaced few weeks ago
No stalling, hesitations, back firing etc.
Filled tank and added STP fuel system treatment a few hours ago
Reset PCM and afterwards the idle was at 800 - 900 for first 5 minutes or so (guessing open loop) then dropped back to 450-475
Checked for Vac leakes via visual inspection but found nothing
The distributor does have bad bushings which will be replaced this weekend. Not sure if this has anything to do with low idle speed as have known about bushings for a few weeks while doing cap, rotor, plugs, wires change and did not have low idle issue at that time.
Is there a way to test MAP sensor or IAC to verfiy proper operation?
Any ideas?
Thank you
IAC and TB have been cleaned (seemed to improve fuel mileage)
Tested TPS with multimeter and appears to be in spec from closed to WOT no sudden drops or spikes. .2 v closed 3.7V WOT
PCM was replaced few weeks ago
No stalling, hesitations, back firing etc.
Filled tank and added STP fuel system treatment a few hours ago
Reset PCM and afterwards the idle was at 800 - 900 for first 5 minutes or so (guessing open loop) then dropped back to 450-475
Checked for Vac leakes via visual inspection but found nothing
The distributor does have bad bushings which will be replaced this weekend. Not sure if this has anything to do with low idle speed as have known about bushings for a few weeks while doing cap, rotor, plugs, wires change and did not have low idle issue at that time.
Is there a way to test MAP sensor or IAC to verfiy proper operation?
Any ideas?
Thank you
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