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Discussion Starter #1
I have changed timing belt, serpentine belt, plugs, wires, ignition coil, and all motor mounts. Car had 151,000 miles on it. Manual transmission. When sitting at a light or just stopped whether on the clutch or just in nuetral the engine has a little shake to it. It runs great, but I have never been able to fix this issue. Any ideas ?
 

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Is the ac on while this happens?
If your car has a Idle Air Control Valve then it could be in need of a test, just unplug its electrical connector. Your idle rpm will change- it could be gummy and some cleaner/q-tips be in order.
If you have a obd2 reader, use it to monitor RPM's while your idle issue is happening.
PCV hoses are a common issue, make sure their not cracked or collapsing
 

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Humphrey mentioned this already, but the first thing I would check is the rear PCV hose that goes from near the ignition coil over to the intake about 6" below the throttle body. It commonly fails at the 90 degree turn where it attaches to the intake.
 

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Discussion Starter #5
Thank you for your replies ! I checked the PCV hose 6" under the intake. With the car engine off it seemed fine. When I turned the engine on it collapses at that location. Does that mean that the hose is weak and unable to hold the pressure ? Do I need to replace this hose ?
 

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Discussion Starter #6
Thank you Humphrey, and FocusKnot. I researched further and found that it was the hose that needed to be replaced. I just purchased the hose from the ford dealership and it came with a new Heat shield around it. I will install it and let you know if this repaired the issue.
 

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Good luck.
 

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Discussion Starter #8
Ok, I replaced the hose, the new hose does not collapse. Maybe it will give me a little bit better gas mileage in the long run but this did not fix the issue. I drive the car in the highway and I think it feels a little different but still when I get to a light and am in nuetral it feels shaky. It never stalled, and doesn't feel like it's going to stall, just feels as if the timing was off the tiniest amount. Looks like I will need jack stands and a lot of patience if I want to clean the IAC. Any other suggestions before I try that ?

Thanks
 

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The IAC is near the throttle body, least I believe it is so no jack stand required.
Check my previous post, you didn't answer some questions.
 

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Discussion Starter #10
Sorry, no the AC is not on during this. No I didnnot unplug iac since I'm not 100% where it is. Did you mean that the electrical connection itself may be gummed up and need a cleaning with qtips, or did you mean the actual removal of IAC and cleaning that ? Yes I do have an OB2 reader I can hook up. Would this be to record the fluctuation of rpm. For example from 450-550 fluctuation?

Thanks
 

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Yes it records if your model reader is good.
the IAC is right under throttle body to the left if you're standing in front of car. Wouldn't hurt to clean electrical connections but the iac it self could need removed and cleaned. Idle after warming up should be in range 700
 

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For IAC location you need to know the engine type.

OP probably has a zetec, unlike the duratec location Humphrey is thinking of for the duratec.

Duratec engine is possible, but the PCV hose is different so I'm guessing zetec here.

IAC on a zetec is on the back of the manifold, quite a bit more difficult to reach. (stretch from underneath)
 

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The more you know.
 

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Lack of info. in the original post, '03's COULD have either engine though duratec isn't likely except in CA emissions states that year.

Your advice was good for either until the question on IAC location.
 

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Thanks sailor. I am learning, I know mostly about my car but as I read other peoples post I start to get a better picture of the overall focus line.
 

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Discussion Starter #16
It is a 2003 Ford Focus 2.0L 16v zetec DOHC ... I put the car up on jacks and removed the IAC from under the manifold and cleaned it out with carb cleaner and qtips. Is this valve supposed to be seated ? Or is it supposed to be able to be moved back and fourth when disconnected from the electric ? I was able to move it back and fourth with the qtip and cleaned it good. I reinstalled it and I still have a stumble when the cars warmed up. It stumbles then surges but it only surges a few rpm. It stays in the 700 rpm range. Any other suggestion ?
 

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Is this valve supposed to be seated ? Or is it supposed to be able to be moved back and fourth when disconnected from the electric ? I was able to move it back and fourth with the qtip and cleaned it good.
The IAC is solenoid operated. The internal spring will push it full open when it is disconnected from electrical supply.

Have you checked your MAF for dirt?
 

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Discussion Starter #18
The MAF when I pull it out when the car is running it stalls out. Did you mean opening it up and spraying it down like the IAC ? No haven't tried that yet. Could it be that the idle is low? Can I just adjust the idle up higher? Could is be a faulty TPS ?
Is there an O2 sensor on the engine ? If anyone else sat in the car they would
Probably think I'm crazy cause it runs good. Just I find it annoying that little shake . Thanks !!
 

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I wouldn't adjust the idle.
The MAF sensor can be cleaned, there is some specific cleaner made just for that. DO NOT DISASSEMBLE THE SENSOR.
Taking it out while running would cause it to die.
TPS should be tested.
 

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Yep

Idle rpm can't be adjusted by the throttle stop screw (if you drill out the plug for access) because the computer & IAC control the speed.

Make a manual adjustment & the computer corrects for it within it's operating range. Only a computer "tune" can change the target idle rpm.
 
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