I have a 1999 T&C Limited, 3.8L, 180,000 mis.

This issue started back in April. The engine would start to die and than catch itself, drop to about 200 rpms and rev up to 1000 rpms repeatedly. At stop signs it sometimes die altogether. Above idle it would run fine.

At this point I took the throttle body out, cleaned it and made sure the EGR valve would function (EGR valve replaced in 2009). This seemed to fix the problem for about a month. Then my symptoms: engine revs at idle returned. After talking to mechanic I checked the Idle Air Valve with an OHM meter and it tested bad and I replaced it. This solved my symptoms for about 2 weeks when the same symptoms returned.

After talking to another mechanic he suspected a fuel issue. I replaced the fuel filter and again my symptoms went away only to return a week and a half later.

I reviewing what I have tried and replaced we noticed one common thing that I was disconnecting the negative battery cable with each repair. So the nest week (this problem most likely happens on Thursdays) we disconnected the neg. battery cable and the problem went away. But again, one week later, on Thursday, the engine revs, battery disconnected, the idle did not go away until 3 or 4 starts.

My problem returned after only 3 days. This last time I disconnected, started again and the idle did show the rev symptom but after revving it via the gas pedal a bit the symptom stopped.

Am I having a computer problem? Vacuum problem that the computer is compensating for? Air? Fuel?

Please help.

 

I have been through the same issues with revs at idle, replaced the same parts and no luck. Does it idle normal when you turn off the a/c?
Sometimes mine revs so bad at stops that the brakes can't hold it.