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1994 Dodge Ram rough idle when cold

Tiny
GARDEKUS
  • MEMBER
  • 1994 DODGE RAM
  • V8
  • 4WD
  • AUTOMATIC
  • 212,000 MILES
Ok I changed the trans in my truck, replaced with a used one. Now truck runs really rough till it warms up.
its not so bad when I put it in reverse. After it runs 15-20 min. It will be ok unless I leave it sit for more then 4 hrs. There seems to be some knocking- tapping coming from trans till it gets warn. But then everything seems ok and runs great. I've changed O2,
tps, cap, plugs, wires, roter, egr most anything that would have to do with engine, and im thinking its got to be trans. Could trans oil presure cause a rough idle untill it warms up?
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Monday, October 4th, 2010 AT 12:47 PM

3 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
The trans won't cause a rough idle when cold. Has the check engine light come on? Have you checked for vacuum leaks?
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Wednesday, October 6th, 2010 AT 12:41 PM
Tiny
GARDEKUS
  • MEMBER
  • 2 POSTS
I've found no vac leaks, it seems to be good everywhere I check. No engine light or codes coming up. Just seems to idle fine when cold if I put it in reverse. Bad when in p, n, and d untill it warms up. Heard someplace that ecm only reads from 3 sensors untill it reaches temp. Just dont know what ones they are. This thing has got me stumped.
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Thursday, October 7th, 2010 AT 11:22 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,867 POSTS
I believe the sensors are the crank, can, and temp sensors. Of those, the temp sensor would be my first guess. Its purpose is to tell the computer the ambient temp and the coolant temp. From that, the computer determines how rich or lean to make the fuel mixture.
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Saturday, October 9th, 2010 AT 12:19 AM

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