surge/almost stall coasting at low speeds

[largnessin]

I have a 93 villager and the rpm moves up and down between 500 and 1000 every 5 seconds or so when I'm coasting at low speeds. If I have lights, wipers and AC on, it will go below 500 rpm and stall.

I've had problems with burned out AC low-pressure sensor and compressors and was thinking that this surging may be the cause, since there is so little power at the bottom of the wave that the lights dim and the fans slow. So both the pressure sensor and compressor would be working way overtime going on and off every 5 seconds.

The idle is fine, steady at between 650 and 750, and reacts correctly (goes up 100 rpm or so for a second) when the AC compressor comes on. Milage is OK (for an old villager) and power is like always. New plugs, wires, distributor/rotor. 117K miles.

Does anyone have any ideas on what's causing the surging?
Any ideas would be appreciated.

Lar

[IH8SPM]

Check your TPS

[slipguy]

Originally Posted by IH8SPM

Check your TPS

have u found problem with stalling. mine is a 94 and does the same thing. i found using bp gas the problem goes away for awhile. it seems to return sporadically. it usually comes back after i have gone on a long road trip. drop me an email at [email protected] if u have come up with a solution.

[IH8SPM]

Check your fuel injectors for leaks and also the idle air sensor. You both might want to have your cars emissions cleaned just to be a sure its not a clog in the fuel system or a bad fuel pump is a good culprit as well

[QuestOverload]

Vaccum leaks, TPS, dirty MassAir sensor and dirty/bad injectors, and low fuel pressure are the first things that come to my mind. The IAC could also be a problem, but I forget what it does. LOL
HTH

Edit: Seafoam is the best additive injector cleaner so far IMHO. I usually add it to a 1/4 tank of gas and use a heavy right foot for a day or 2. I'd try that first, as it's easiest and cheapest. Also, an idle between 650-750 isn't steady!

[IH8SPM]

The IAC valve controls the amount of air to fuel mixture there is. IT is located on the intake (big silver thing against the back wall in the engine compartment.) It has two or four screws and two plugs that are held in place by two small snap clips that can get lost if you are not careful. If you remove the unit just place it in a bucket or somethig filled with fuel injector cleaner. After a few minutes remove it and use a small brush to clean off the debris(carbon build up). replace and go. It may not be your problem but that is what it is and how to fix or temp fix a problem with it.