Why won't it sloww down?

[danman2]

Here is what is happening. While driving on the highway my rpm's are at 2000 rpm and when I take my foot off the gas pedal the rpm's will go down to 1800 then rev up to 2800. When I slow down it will stay high also. This doesn't seem to happen when I first start the van.

[RIP]

What year, type engine? Gr Caravan, Voyager, or Town & Country? Any recent maintenance? Getting a check engine light (CEL). I think it's a MIL light on older models. Need to include basic info like this in any post.

My guess is something is driving the throttle plate or the intake air control valve (IAC) when it shouldn't or there is a vacuum leak.

First step is to inspect the throttle linkage and make sure it's not rubbing or binding on something and what is visible is clean. Second, inspect all the vacuum hoses you can find. Look for cracked or disconnected hoses. Third, go to Autozone and have them download any stored fault codes with a DRB II scanner. Should do this for free but call to make sure. This only works on 96s and up - I think. Once you have the codes come back here.

You'll get more info with the scanner but, you can get basic codes in your driveway. Turn the key from off to on three times, leaving on. Watch for a series of flashes from the CEL on the dash. A code 21 would be two flashes followed by a single flash. All codes are two digits. Should finish with a 55 code.

[danman2]

It's a 93 gc 3.3l. Not getting any check engine light and not getting any fault codes. Was gettting o2 and erg faults and have changed them both. At times it well hesitate also. Thx

[RIP]

Ok. You're way ahead of me. Now I'm leaning toward a vacuum leak. Not familiar with 93s but, if the throttle plate is driven by anything associated with a vacuum source either directly or indirectly, I would start there. There may be some useful info here: http://www.autozone.com/servlet/UiBr...ginRepairGuide Just click on the headings then go to the list on the right.

Might consider cleaning the throttle body. Many swear by this stuff called SeaFoam TB Cleaner. Seems to work great. You can search the forum and find more on that.

Once that's done I would move back to engine electronics. According to several on this forum just because you're not getting a CEL or code doesn't mean a component isnt failing.

[danman2]

Thx, will give that a going over in the next couple of days and go from there. Will post results.

[RIP]

I had the wrong Autozone link in the previous post for a while. The correct link is there now. 23 Oct 12:47am Pacific.

Plus I forgot to explain why a vacuum leak. When you let off the throttle and/or slow down vacuum normally climbs rapidly. A particular component may be sensing the vacuum isn't climbing as usual because of a leak and is sending a command to open the throttle plate or air intake valve to compensate. Just a theory.

[danman2]

Thanks for the advice. Found a vaccum leak under the battery holder and this explains why my cruise wasn't working when I tried it.

[danman2]

Discovered that after I posted the problem. All is good now.

[RIP]

Glad to hear all is well. Thanks for posting the fix. Cheers!