Intermittent surge at idle

[kloog]

I'm having a hard to solve problem with a car that has intermittent surging at idle. It idles fine but ever 2-4 seconds (randomly) surges to about 1,000 rpm and drops right back down. All the standard tune-up stuff has been done. It occurs while in closed or open loop, no codes.
the car is a 1995 escort 1.9 130,000 miles.

Does anyone have any tips, thanks in advance.

 

[mechtech2]

All vacuum lines must be perfect, especially the PCV system.
Clean your throttle bore and plate real nice, and yank the idle air control motor and clean it as well. Don't use strong solvents on the IAC or you could melt plastic parts.

 

[punisher]

To add, after doing what mechtech2 said, disconnect the battery to reset PCM memory and reset idle strategy.

 

[mechtech2]

punisher - Good point, but kloog be aware that is may idle goofy until it relearns a few parameters.

 

[kloog]

wouldn't that cause a set idle problem that occurs at regular intervals not randomly, the vacuum or a sensor being broke i mean.

 

[Triple_Se7en]

Vacuum lines cracks or criss-cross. Also check the fiber elements in your air filter housing. They could be blocked, missing or wrongly inserted.

 

[Panzerman]

On some Fords there is a Idle control valve that is located on the side of the thottle body, it looks like a cellenoid. Go to Ebay and search under Ford Escort idle control valve, see if a picture of one comes on and trace it to your thottle body, you can clean them or I bought a new one for $40 for my wifes Lincoln at Advance Auto. It will cause what you are saying. They are bolted on the side or the top by ussually two small bolts, check it out.The whole thing comes off, it has a wire plug in to it.