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Discussion Starter #1 (Edited)
My Zetec ZX3 just started idling very rough when it is cold...1000rpm, then drops to almost nothing, then surges up to 800-1000rpm....and so on and so on.... When you step on the gas it revs up normal, but idles like crap.

There is so little vacuum created(cuz of low revs), that I don't get brake assist during those times. Also, it makes my tranny shift funny(ATX)--missing shifts from time to time like the tranny is giving out. At 60mph, it can't make up its mind on what final gear it wants to be in....in and out of top 2 gears....but ok at other speeds. On the hiway, I can put it in N and watch the revs slowly climb up to like 2,000rpm for like 10 seconds and then drop down to 800rpm.

And THEN, at random times, it runs normal.....WTF?

No vacuum leaks---replaced the typical 'problem' hose behind the throttle body last yr and have now checked for leaks---none found. MAF, TB position sensors test OK. No Codes yet. Idle Air Control Valve maybe? Help?!
 

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usually when you idle air control goes your car will not want to hold an idle and die on you. When my 02 sensor went on me my idle was really and would want to die a lot.. sometimes it did. Have you done anything under the hood lately? You could also clean your MAF. That would mess with your idle def.
 

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mine has the same problem im trying to figure out whats goin on
 

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could be PCV valve thats what my prob was (my old car did the same thing). could be a number of things tho idle control valve, maf, or 02 sensor. ive heard alot of foci have this prob.
 

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When it's idling like crap, crank the steering all the way to a lock on one side and see if it dies. If it does, then it's an IAC problem. The IAC should boost the idle when you crank the wheel to a lock, or when you turn on the AC.

The lack of power brakes feel is a symptom of both low engine speed and lack of vacuum. That doesn't really tell you anything more than you already know.

If you can hear a sucking sound in the passenger compartment, then it's more likely to be a worn out brake booster. That happens with time, and is accelerated if you spill brake fluid on the outside of the booster.
 

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Idle Air control
 

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Discussion Starter #9
Thanks for the inputs so far guys

Thank you fellow FF !! [loveff]

Yeah, thought about the O2 sensor, but usually you see a jump in gas consumption, rich exhaust smell, varying low and high idle....none of that noticed. MAF -- clean and inspect it every few months.

Note to all though... I disconnect the IAC, and it runs smoother; no more bouncing of idle speed. So are we all going to the same conclusion of bad IAC?

One funny thing though is that my IAC has an angled connection(90 degrees from the IAC body --- pointing to the firewall). I looked at a few online and they have a straight connection -- pointing to the driver side fender. ----I don't think my wires are long enough to reach it?!?
 

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I wanna add my previous experiance to this, I had a bad EGR Solenoid that caused my idle to bounce exactly like this and had no brake assist below 1200 rpms, it threw a cel though about excessive egr flow. The solenoid was completely shot and once i replaced it brakes come back and idle was perfectly stable.
 
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