RPM fluctuates when coasting

[ziaduck]

I recently picked up my 1995 Villager from the shop after having the timing belt and water pump replaced. The van has 116K miles, and has been well maintained.

When driving the van tonight I noticed that the RPM's would fluctuate between 500 and 1000 RPM when I let off the gas pedal or approched a stop. The engine is so quiet I wouldn't have noticed without the Tach. The van runs and drives fine otherwise.

I don't believe the problem is directly related to the timing belt/water pump, but perhaps something was moved/damaged/not re-set/etc after the work? What else should I look for? Thank you!!!

[dzus]

My 97villager (108,000 miles) had the same problem last week and I replaced the throttle position sensor. The rpm fluctuating stopped and also shifts a little smoother. I used a OEM tps #c7012-131469,$102.00 at autopartsworld.com. You can find cheaper aftermarket tps,but I prefer oem for sensors and such.
dzus

[ziaduck]

Thank you for the tip. Is there a way to test the TPS? I have the Haynes manual, but have not had time to reference it this morning. Isn't there another throttle sensor which works off of the cooling system? Is it possible that there is air in the system from the water pump replacement, and that is causing the problem? All feedback is greatly appreciated!!

[dzus]

Cooling system has 2 temp sensors;1 is for temp gauge and 1 is for the computer. Air in the coolant would cause the van to over heat. None of these would effect the rpm's to fluctuate.
I found my tps bad by increasing the rpm's very slow & steady to about 2,200 rpm then back down the same way. My rpm's went up good,but coming back down it would drop quickly no matter how slow I went. I unplugged both connectors on the tps and re-checked. The rpm's went up & down just fine so I replaced the tps. There is a resistance check for the tps,which I did and it checked ok.......go figure.
dzus

[ziaduck]

Thanks, Dzus, I'll give it a shot tomorrow. I checked with Autozone today and their price for a new TPS is $49.99. less than half of the dealer cost. So if it is bad, at least it's not terribly expensive.

[manythreads]

My 94 fluctuates and also stalls, I tried an used IAC valve & it went away for a while but now is back.