95 3.8 occasional surging

Hi all,

This van has been in use since late December after replacing one of the heads and a whole gasket set. No major problems, even with the trans. One thing that is bugging me though is this surging that happens once in a while when at idle speed. This only seems to happen when the van is not moving, doesn't matter if it is in gear or not. The RPM's will jump to 1400 or so, then sink so low that the oil pressure light will flicker on and off. It seems to do this 3 or 4 times, smooth out for a few seconds, then repeat. I was first thinking maybe the TPS was dirty or defective, but viewing live data on my code reader put that theory to rest, the TPS showed the exact same value during the surging. This might happen on 1 out of 4 trips, and might only happen for part of a trip. I took off the idle air actuator and made sure it was clean, it had very little dirt in it. I do have a persistent 171/174 error, but I don't think this is the cause. My next step is to check the injectors to see of there is any air leaking around them which could cause the surging, and maybe also the 171/174. Any other ideas? Thanks everyone!!

Little more info on this problem. Paying very close attention to what's going on, there is a distinct click that I hear just before the surging starts, sounds like a relay somewhere near the passenger side area of the firewall.

At first I thought it may have been a cooling fan relay, but I turned the AC on and both fans ran with no trouble.

OK, haven't had a chance to look at this yet since I hurt my back the other day, but here goes. The Windstar only has this surging problem after it has warmed up. That combined with the click I'm hearing just before the surging starts is leading me to believe that somehow the dropping resistor for the low-speed fan operation is shorting or causing some other fault. Would I be able to put a jumper wire in the harness to bypass the resistor and just have the fans operate at full speed? With summer coming up I don't think it would hurt too badly. I am going to stop at the local dealer though and see how much this resistor costs.

i'd say tps is bad. i had the same problem up and down up and down so replace cps still done it then i put tps on it and it runs fine..175000 on it now and it's a 3.8....good luck...

The TPS should be fine. Scan tool showed no changes in TPS position during the surging, if it was giving false readings to the PCM it should show up on the scanner. I'm going to work on the van tonight and will post back as to what I find.

Is the ac coming on and "loading up" ... or is the ac clutch falling out right away? Could be the engine is expecting the ac load ... and the ac load ain't there.

I don't think it is the AC, all the HVAC controls are turned off. I though I had it licked, after jumping the bad radiator fan resistor I took the van for an hour drive, no problems. Wife took the van the next day, and it started surging again at idle, in or out of gear. The sound I thought might be a relay actually sounds like a single metallic pop noise, like a paint can expanding on a hot day. As soon as you hear this sound, the engine starts its surge cycle. Of course I can never get it to do it while I'm under the hood, that would make it too easy.