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2008 SES - Rough Idle

19K views 12 replies 6 participants last post by  sdg3205 
#1 ·
I saw other threads with the same questions but I've also read you guys like people to start new threads.

If I'm waiting at a light the idle is quite rough, with about 300 rpm fluctuation. Runs fine at speed. Happens in Park or Drive, with or without AC. It has been gradually getting worse. The car has 100,000 KM (62,000 miles).

Any thoughts?

thanks so much
 
#2 ·
IIRC, the idle fluctualtion is the ECU trying to find the idle sweet spot. And AFAIK, all of the 2nd gen cars do it. It could be an engine mount going bad. How low is the RPM?
 
#3 ·
Thanks for the swift response!

It seems to drop a little below 500 rpm when fluctuating. I'll get some more exact number in a bit.

I'm going to grab some MAF sensor cleaner and 4 new plugs after work today.

Just had the oil and air filter changed.
 
#4 ·
That should improve the efficiency of the motor, but I doubt it will help the idle issue. Basically the ECU is trying to lower the idle speed till it senses a stall. Then it jumps back up. Rince/repeat, causing the uneven idle.
 
#8 ·
...If I'm waiting at a light the idle is quite rough, with about 300 rpm fluctuation. Runs fine at speed. Happens in Park or Drive, with or without AC. It has been gradually getting worse. The car has 100,000 KM (62,000 miles)...
Hi sdg3205,

Swing by your dealership so they can inspect. Ford certified techs are specially trained to diagnose and repair your Focus.

IIRC, the idle fluctualtion is the ECU trying to find the idle sweet spot. And AFAIK, all of the 2nd gen cars do it. It could be an engine mount going bad. How low is the RPM?
...it seems to drop a little below 500 rpm when fluctuating. I'll get some more exact number in a bit.

I'm going to grab some MAF sensor cleaner and 4 new plugs after work today.

Just had the oil and air filter changed.
That should improve the efficiency of the motor, but I doubt it will help the idle issue. Basically the ECU is trying to lower the idle speed till it senses a stall. Then it jumps back up. Rince/repeat, causing the uneven idle.
Mine idles smooth as glass. Occasionally, it'll drop down to 400 for a second, then recovers quickly. Only once has it actually stalled.
Thanks for all the good info, folks!

Crystal
 
#9 ·
I'm doing a Focus service day tomorrow.

I'm picking up some Mercon LV today, so tomorrow the tranny fluid and filter gets changed, the plugs get changed and re-gapped, ECU gets reset, MAF sensor gets cleaned. Will it help? Probably not but it will cost less than $200 before i give up and go to ford. At least the door locks dont seem to stick anymore.

My 1981 DeLorean runs smoother than my wifes focus. I do love the focus though. Very comfortable to drive, great on gas, looks nice inside. I drove (and still have) a 2000 Jeep Wrangler. Getting back into the Jeep feels archaic compared to the Focus.
 
#13 ·
Update

Some very unnerving findings today.

1. The spark plugs were toast.
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The car has 100,000 Km on it and i bet these are original. We bought second hand but it goes to show you can't depend on PO's for good service history.

2. One of the spark plug wells was COMPLETELY full of oil. Is a new valve cover gasket kit required?

Thanks folks!
 
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