1998 Dodge Caravan

Tiny
PEARLDRAGONCHYLD
  • MEMBER
  • 1998 DODGE CARAVAN
Transmission problem
1998 Dodge Caravan Automatic 140000 miles

I just had my transmission rebuilt. When I got it back it idles erracticly when the engine warms up then when I come to a stop it dies. We have done a tune up(replace plugs wires, distributor, new air filter) also we have replace the throttle postion sensor. Any ideas what the problem could be?

thanks,
Tia
Do you
have the same problem?
Yes
No
Monday, March 9th, 2009 AT 1:06 PM

4 Replies

Tiny
JAMES W.
  • MEMBER
Tia, do you have a check engine light? If yes, I would need to know what code # and the description. My first thought is a gross vacuum leak. You want to check all your vavuum hoses for splits or disconnects, especially around the transmission area. Hope this helps.
Was this
answer
helpful?
Yes
No
Monday, March 9th, 2009 AT 1:23 PM
Tiny
PEARLDRAGONCHYLD
  • MEMBER
Check engine light is not on. No codes come up on the scan tool. Have also checked for vaccuum leaks. There are not any.
Was this
answer
helpful?
Yes
No
Monday, March 9th, 2009 AT 6:58 PM
Tiny
JAMES W.
  • MEMBER
My first suspect would be the idle air control motor IAC. It's mounted on the throttle body unit. This little unit's main purpose in life is to control the engine idle speeds to compensate for AC, power steering, cold fast idle, etc. It may just be carboned up and just need cleaning. This can be done by removing the unit and spraying it down with an ordinary can of carb cleaner. Hope this helps.
Was this
answer
helpful?
Yes
No
Monday, March 9th, 2009 AT 9:17 PM
Tiny
CARADIODOC
  • EXPERT
One more simple thing to not overlook. You didn't say how long ago or how many miles since the rebuild. They would have disconnected the battery. After that, minimum idle must be relearned by the engine computer. Until this is done, the computer doesn't know when you have your foot on the gas pedal and when it must be in control of idle speed.

It knows your foot is off the pedal when you're coasting. The strategy it uses is higher than normal manifold vacuum for seven seconds. High vacuum will occur if you snap the throttle open and closed real fast, but not for seven seconds. You have to coast down from highway speed for the high vacuum to occur for seven seconds or longer.

When these conditions are met, the engine computer looks at the voltage from the throttle position sensor and puts that in memory. The next time it sees that same value, it knows it has to control idle speed.

Most technicians will perform a test drive specifically to prevent this customer complaint after doing any work that requires disconnecting the battery.

You may have met the relearn conditions by now, but introduced another problem by just changing a bunch of parts without diagnosing the problem first. Specifically, by throwing a throttle position sensor on it, the sensor voltage at idle will be different than before, possibly by only a few hundredths of a volt. If the computer ever sees a voltage lower than before, it will put that into memory, but if it never goes down to the voltage it saw with the old sensor, it assumes you are holding your foot on the gas pedal so it lets you control idle speed.

There could be a lot of other causes of erratic idle, but expect to have to just drive the vehicle if the battery is disconnected again.

Caradiodoc
Was this
answer
helpful?
Yes
No
Tuesday, March 17th, 2009 AT 10:44 PM

Please login or register to post a reply.

Recommended Guides