My wife’s 1997 Ford Escort suddenly started having idling problems today. Basically, whenever the car was fully stopped or in park it would idle up and down, hovering over stalling and eventually doing just that. However, it would have no problems restarting after the stall.
Initially I thought the problem was related to the status of motor oil… but that’s another issue. Topping off the motor oil to the appropriate level did nothing to correct the idling problem.
After that disappointment I started noticing a hissing, or air-sucking noise coming from somewhere around the engine. This turned out to be the key.
I found a small hole in the L-bend of the PCV hose, which sits along the top-back of the engine on this particular Escort model. I put my finger over the hole and the engine suddenly returned to normal idle. The L-bend piece was actually caved-in around the hole, so proper repair would mean replacing the PCV hose or PCV hose and valve, depending on how Ford sells the parts. However, with one day left in the work week I temporarily repaired the L-bend with an abundant wrapping of black electric tape. This seems to work and will hopefully keep the car running properly until I can replace the PCV part or parts on Saturday.
You can read more about the interesting history and functionality of the PCV valve at Wikipedia.