I have a 3.3L 2001 Caravan. I noticed to things with my van a couple days ago. 1st thing was that when I was slowing down and coming to a complete stop, I would get a thump, like it felt like someone had bump me from behing. I did alittle research and I guess they called it "bump shift". So I changed the 2 speed sensors on the tranny and so far I haven't felt it.
The 2nd thing I noticed is that my RPM fluctuates when I'm driving arund 40-50mph. Engine sound would sound normal at first, then the rpm would jump about 500 like I'm climbing a little hill, then back to normal, then back up again. I changed TPS and it still does it.
But 1 thing I did forget to do after replacing my TPS, was resetting the pcm. So I'll disconnect the negative terminal on the battery, turn the key to crank, and try to take the van out for alittle test drive again to see if it happens again.

 

Try to clean the Idle Air Control sensor, too

 

I never got a chance to take my IAC out yet, but I'll make sure to give that a try today.


Ok, so I shot the throttle body with some throttle body, carb cleaner yesterday. My wife took the van out this morning and the RPM still fluctuates, but in addition to the fluctuating rpm, the rpm jumped at around 4000 and stayed there till she released the gas pedal. So she had to drive at around 30mph on a highway just to keep the rpm level at around 2000.
When she pulled up to a paking lot and placed the vehicle in "P" the rpm idled at around 1500.
Now I'm not sure if it's because I resetted the pcm, so it's learning the person's driving habbit again, or could it be that the tranny is going bad/slipping?

 

If if were the tranny starting to fail, you'd definitely feel it before anything, and I highly doubt that the rpms fluctuating has to do with the pcm relearning driving habits.
But the 2 biggest things that I've encountered with this problem have already been mentioned...the IAC and TPS. Definitely clean the IAC. Take it off carefully and use q-tips with carb cleaner on it to clean it off.
When it comes to the TPS, there are a lot of people (including me) that bought new ones which turned out to be defective. Remove and return it for a different one

 

GreenDak22, I really appcreciate you helping me. I'm off of work in about an hour I'll make sure to get on those 2 things. I'll post updates after a test run...thanks.

 

May be a torque converter on it's way out. It will lock right around 40 - 45 mph.

 

Ok, I was going to just clean the IAC sensor but wife suggested to just replace it so she got a new IAC. I replaced it. Van started, idled normal. Took it for a drive, and it did still fluctuate, however I did not experience the other problems my wife did. The van only fluctuates from 40-55mph. Drives normal at lower speeds, but I didn't try driving at faster speeds.


Could that be the problem. That's just about the speed where my rpm start to fluctuate.

 

ok, its been awhile so here's the update.
Van went in limp mode. Took it to a tranny shop. The van gave him all kinds of codes coming from the tcm. So he clears the codes, drives it around and checks for codes again, and all kinds of codes pop up once again. So he suggests it's the TCM. We order a new TCM, van drives perfrect.
Now, a couple of weeks later, the van starts to bump shift again. Could it be the transmission solenoid?