'08 Engine drops below 500rpm, even stalls, on power draw from electrics

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gavin T

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when i raise the windows up, if they are already up and i try this the truck will stall or rpms drop below 500 and it basically stalls. if im comming to a stop and using the steering like coming into a parking spot some times the truck will stall. its got plenty of power on road.
sometimes on cold start. (not heat soak) the truck will idle really rough like its missing till the cylinder picks up. it runs fine after that.
downloaded FORSCAN and see no MISSES after checking for week during drives and after. not MIL.

also when the car is off (sometimes when its on) the rear window struggles to go all the way up some times, and then drop all the way back down.

any thing i can be looking for here to diagnose? i replaced the battery 6months ago the old battery way 6 years old.
 

Dan B

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First, I would remove and clean out the throttle body and see if that helps (I don't think this year uses a IAC valve). Then I would test the voltage at the battery engine running, idle. Then have someone hit the window switches while still checking the voltage and see how low it drops. It could possibly be an alternator problem where it isn't putting out enough voltage at idle but plenty while cruising down the road.
 

Todd Z

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Dan hit the major points, Something is loading the engine... have a TRUE alternator test done, Load, volts and diodes too.... Clean the TB,,,, Take it off and do it.... Also move the tb with your hands and see if it moves smooth... There is NO iac as mentioned so it could be the TB or electrical.
 

Steve Brothers

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Yep. Probably more than one issue here. Take off the throttle body and carefully clean it with throttle body cleaner. Once that is taken care of. Then check the electrical, as suggested by others.
 

Tylerxp2

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Yep. Probably more than one issue here. Take off the throttle body and carefully clean it with throttle body cleaner. Once that is taken care of. Then check the electrical, as suggested by others.
I had a Plymouth that did that too. Alternator was on its why out. Check voltage from Alternator as well. Hope that helps eliminate another reason or cures it. Should be around 14 volts while ST is running at the battery.
 
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Nothing worse that a single symptom, low rpm and stalling when loading the electrical system, that can be caused by a multitude of different problems.

On my 01 had the same symptom and finally traced my problem to the the rubber elbow that connects the PCV valve tube to the intake manifold. It had aged to where it would leak air into the intake but only while idling when the vacuum is the highest.

Like indicated in this thread there were no codes
 

Tylerxp2

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Nothing worse that a single symptom, low rpm and stalling when loading the electrical system, that can be caused by a multitude of different problems.

On my 01 had the same symptom and finally traced my problem to the the rubber elbow that connects the PCV valve tube to the intake manifold. It had aged to where it would leak air into the intake but only while idling when the vacuum is the highest.

Like indicated in this thread there were no codes
I had to replace a strangely shaped vacuum hose on the driver's side that the Dealer wanted $85.00 for in 2011. now that I think of it. similar symptoms. I Replaced it with some German cloth braided vacuum hose and its still pliable. I use it for all replacements now. My guess is try spraying starting fluid around areas of vacuum hoses near you exhaust manifold that would dry out hoses to see if your RPMS rise. Just what I have done in the past to eliminate my vacuum leaks on all my vehicles.
Hope that helps.
[Just short bursts. Dont paint the engine compartment for safety]
 

gavin T

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I had to replace a strangely shaped vacuum hose on the driver's side that the Dealer wanted $85.00 for in 2011. now that I think of it. similar symptoms. I Replaced it with some German cloth braided vacuum hose and its still pliable. I use it for all replacements now. My guess is try spraying starting fluid around areas of vacuum hoses near you exhaust manifold that would dry out hoses to see if your RPMS rise. Just what I have done in the past to eliminate my vacuum leaks on all my vehicles.
Hope that helps.
[Just short bursts. Dont paint the engine compartment for safety]

any photo of the hose yo replaced i would be curious if its this. all the plastic in my engine bay is TOASTED lol
 

gavin T

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I had a Plymouth that did that too. Alternator was on its why out. Check voltage from Alternator as well. Hope that helps eliminate another reason or cures it. Should be around 14 volts while ST is running at the battery.
just tested. here's my results
14.2V at the battery while idling.
13.8V with load from windows at idle
car off 12.4V at battery
car 11.9V car off with load from windows
 

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