I've had this issue happen twice, and now I'm quite concerned.

Was heading down the highway the other day at a steady 55 or so, slowed down to make my turn, but upon lifting off the gas pedal, I kept on going at 55. Thought maybe the floormat got caught or something, so I lifted the pedal with my foot, and shockingly that didn't stop it.

So at this point I'm kinda freaking out, since I'm in an unstoppable van the size of titanic with traffic around me. I slam down the gas pedal multiple times, thinking maybe the cable is just crapping out, but it just returns to it's 55 mph position. I'm in the right lane now and am about to kill the engine and just coast down the shoulder, but then all of the sudden it decides to function properly and finally backs off.

I've got a short clip here that might explain it all better, plus some other odd noise I've noticed as well:

http://www.youtube.com/watch?v=gqLrR...ature=youtu.be

I'm curious now if that "piston" thing is extending for some reason while I'm driving, and is causing the throttle to stay open. The cable seems fine, and the pedal returns as it should.

Any help on this would be greatly appreciated!

 

That pintle on your idle speed actuator motor is not working as mine does, at least when turning the key on and off.
It is also sometimes called the Idle air control valve, or the idle speed (control)motor.

The computer might have stored some codes relating to this. Do a search for 'Key Dance' to check them.

They cost from 44 to 120$ on rockAuto, under fuel/air.

Also there is a connection at the throttle lever for the throttle rod which goes back to the transmission to tell it throttle input to help it to decide when to shift. This is designed to slide on the rebound. If it is not sliding, then the transmission lever might be holding the throttle open, and might possibly have contributed to the idle motor not working properly.

 

I always thought that "piston" device was used to raise the engine idle when the engine is cold, or when the A/C compressor is switched on. When the A/C clutch engages it creates additional drag on the engine and the idle needs to be raised to keep the engine RPM up around 750-800. The IAC is located in the base of the throttle body, so I'd say this piston device would be the Idle Control Motor. I don't think that piston could extend enough to keep the van running at 55 MPH in top gear though.

The transmission cable that landyacht318 refers to is called a Detent Cable. When you floor the throttle the Detent Cable pulls a lever either in or on the transmission which puts you into a lower (or passing) gear temporarily. I don't think your year van has a detent cable -- but it is worth checking just in case. Based on your video I think the metal bar you see running from the throttle linkage down to the transmission is your detent -- but in your case it is a metal rod instead of a cable.

If your van has Cruise Control you may wish to check the cable connections coming from that for problems. Maybe disconnect the Cruise unit to see if this solves your problem?

This is a dumb question, but here goes. When the van was cruising along at 55 MPH did you ever step on the brake? If it was the Cruise unit then stepping on the brake pedal should have disengaged it if it was in fact engaged. Just a thought.

 

Thanks for the replies.

This is a tricky thing to test for, since it doesn't always happen, and I cannot get it to stick when the van is safely parked and not running.

This "detent cable" (or bar, in my case) was slightly rusted to the bracket. I broke the rust free and added a bit of oil to get it moving again. I test drove it for a bit around the 55 mph mark and couldn't get it to happen again, so I'm hoping this has fixed the issue. As I said before though, this is hard to check since it doesn't happen frequently. To be safe, I'll also disconnect the cruise control cable when I get home this evening. It's never worked anyway, so I'm not too concerned. I'll also do a key dance check and see if I can get a code for this idle-motor-piston thing.

And Rusty93, I did hit the brakes a few times thinking that maybe the cruise had malfunctioned, but it didn't seem to do much other than cause the van to have a herky-jerky road seizure... Heh

Also, while I'm here, is the speed sensor close to where the detent cable/bar connects to? I see some wires going right back behind the bracket. I was told to check this sensor regarding my no-overdrive issue, but didn't want to pull the wrong part out.

Thanks again for the help.

 

While my Speed sensor ('89)is on my speedo cable, i believe your only VSS is on your transmission. Later models have one on the differential in addition or alone.

Your cruise control might be inoperational due to a vaccuum leak. Vacuum leaks generally effect engine performance to some degree so inspect all the vacuum lines, and you might gain a little mpg.

 

I'm thinking it's an electrical issue with the cruise since the light never kicks on. I do know if I have the air on and I go up a hill, it will decide to vent out of the floors instead, and once I reach the top of said hill, it comes back out of the proper vent. I'm pretty sure this is a vacuum issue somewhere.

Just another odd issue on my list of van fixes... heh

 

This is a common issue - you have a bad one-way vacuum valve between your intake manifold and the vacuum feed for the A/C. Tons of previous threads on the forum dealing with this, where the valve is, how much it costs, Mopar part #, how to replace etc. etc.