3.9 runs rough until warm
#1
12-31-2011, 08:42 PM
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3.9 runs rough until warm
Hello to the forum; happy new year! Have a '95 Dakota with 3.9 and automatic. Starts fine and idles good at first. Quickly begins to stumble but usually continues to idle. Trying to drive off will make truck run rough and most likely stall. Wait approximately 20 minutes allowing temperature to come up to mid-gauge; idle settles out and you can drive away without problems. Changed O2 sensor because Check Engine indicated problem; no Check Engine light since yet problem just described remains. Let it come up to temperature and she runs just fine... Any ideas?
#3
01-04-2012, 08:28 PM
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Humm... I would think that a vacuum leak would not appear at start up, kick in shortly after running, clear up after 20 minute warm up, and not cause any farther issue thereafter. Any suggestions on how to remove this as a possibility are certainly welcomed. As for the temperature sensor, the temperature gauge works perfectly; bottom scale at start to mid scale after warm up. Thanks for the consideration.
#4
01-04-2012, 10:52 PM
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#5
01-06-2012, 08:45 AM
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i'd follow what crazy said...
someone told me once that a bad head gasket can cause that too, but once the truck warmed up it would blow out way more white smoke than normal and smell really wierd.
and never trust a temp guage. my old dakota overheated once and after that my guage went up to the halfway point and wouldn't move at all. after i replaced it for kicks and giggles i found that the truck was still overheating(which it felt like it was doing anyway which prompted for the new sensor).
someone told me once that a bad head gasket can cause that too, but once the truck warmed up it would blow out way more white smoke than normal and smell really wierd.
and never trust a temp guage. my old dakota overheated once and after that my guage went up to the halfway point and wouldn't move at all. after i replaced it for kicks and giggles i found that the truck was still overheating(which it felt like it was doing anyway which prompted for the new sensor).
#6
01-07-2012, 10:14 AM
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Warm engines run better because tolerances are reached. Other reasons for poor idle can be caused by the sensor for the PCM, IAM can be crudded and not quite right, or even defective, wiring to these units could be frayed, EGR valve could need cleaned or replaced, vacum leaks, just a host of things. I read so many posts where lots of parts have been changed to no avail.