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2003 Focus 2.3L Duratec.

Engine warm or cold, the engine idle will be normal and then suddenly "chug" and drop rpm quickly and then recover back to normal RPM's. Running the AC on fan speed 4 can almost cause the engine to stall. Flipping between speed 3 and 4 can reproduce the problem. The engine normally idles around 800 rpm and drops to 500rpm and then recovers.

A few months ago I had a CEL that led me to a dried out vacuum line on the two valve bodies right on top of the intake manifold. These control the Intake Manifold Runner Control (IMRC) flats. I mention this as it could be related.

Research has pointed me to the Idle Air Controller (IAC). I have removed this part located near the throttle body and cleaned it out with throttle body cleaner. Same symptoms persist. I was not able to move the mechanism inside in or out. Not sure if it supposed to. I need to purchase a voltmeter and see if this is working as it should.

Looking for other vacuum lines that have a crack is also a possibility. There are two line that go to the IMRC valves on the top of the intake manifold route to the underside of the intake manifold and are difficult to see. I can not hear a hissing leak.
 

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The front of the intake is where the imrc/imtv gets their vac to the solenoids which are at the top of the i/m.....You'll find the vacuum actuator behind the t/b w/ the vacuum line hooked at the bottom of it. With the motor idling, Flip the t/b w/ your hand & you'll see the little imrc/actuator linkage move up/down.
 

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The vacuum actuator that is behind the throttle body works if the engine is rev'd past ~40% throttle. I can see it come up abruptly and then drop back down when at idle.

This means the solenoid and vacuum lines are working I suppose? There are two solenoids on top of the intake manifold though. Is the second one connected to another actuator?
 

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The vacuum actuator that is behind the throttle body works if the engine is rev'd past ~40% throttle. I can see it come up abruptly and then drop back down when at idle.
Yea that means its working......
This means the solenoid and vacuum lines are working I suppose? There are two solenoids on top of the intake manifold though. Is the second one connected to another actuator?
The imtv operates the valve for the d/r (dual runner)....The short runners are for the higher rpms & the longer runners are from idle to mid range. Works the same as the svt, but is vacuum operated vs electrical (motor hooked to a linkage) You'd have a cel on if it isn't working. btw if it wasn't working most likely the solenoid.
 

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So what do you think I should check out next?

I need to grab a voltmeter to check that the IAC is actually operating. I have read I can try unpluging it while the motor is running to see if there is a change in RPM.

I'm going to check spark plugs for the heck of it as well.
 

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Do you have a vacuum leak? It very well could be the pcv hose hidden behind the i/m. Use Denso it20's for the plugs.
 

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When cold does the motor have a high idle at first & slowly come down?
 

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Check the PCV hose buried below intake, a common duratec idle issue.

So many expect the IACs to do it but.................one needs to carefully analyze the quality of the idle. IAC generally affects SPEED ONLY, if the engine can be detected as misfiring or very erratic then may not be IAC, more the sign of an erratic air leak (vacuum leak). Most IACs are changed for nothing but then nobody pays attention to a detail of the idle quality, lottsa money wasted there.
 

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Discussion Starter #11
Check the PCV hose buried below intake, a common duratec idle issue.

So many expect the IACs to do it but.................one needs to carefully analyze the quality of the idle. IAC generally affects SPEED ONLY, if the engine can be detected as misfiring or very erratic then may not be IAC, more the sign of an erratic air leak (vacuum leak). Most IACs are changed for nothing but then nobody pays attention to a detail of the idle quality, lottsa money wasted there.
I'll check the PCV out this weekend. I can not hear a very loud audible vacuum leak. I have tried spraying some carb cleaner around the intake manifold but it sounds like the PCV is pretty buried under the intake manifold.


I may change the plugs to those recommended as well as I have experienced in other cars not being happy with other types of plugs.

Mileage seems to be around 20 mpg all city driving too which seems low.
 

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Although it was more obvious of a fix, my IMRC had one of the vacuum nipples sheered off of it, meaning absolutely no vacuum, and produced a persistant CEL (P2004). After purchasing a new one for about 8 bucks, no more light. Although, mine wasn't causing any rough idle. A new ignition coil boot solved that particular issue.
20170920_153928_1522490691120.jpg
 

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You generally do not hear vacuum leaks, they have to be a certain peculiar type to make noise, the edges of the hole determine that.
 

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Discussion Starter #14
You generally do not hear vacuum leaks, they have to be a certain peculiar type to make noise, the edges of the hole determine that.
I tired to spray some throttle body cleaner around vacuum hoses and didn't hear a change in engine rpm.
 

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Do you have a vacuum leak? It very well could be the pcv hose hidden behind the i/m. Use Denso it20's for the plugs.
I was looking at plugs. Motorcraft SP492 (22Y) are the recommended OEM replacements and are gaped at .051. The Denso IT20 are gaped at .044.

Just wondering why I should get the Denso plugs before dropping $35.
 

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They run better in a mzr motor then the Motorcraft ones.
 

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I look forward to post-back here in this thread when I have more time; just too busy to atm. I'm posting here now to comment about Felix comments about spark plug, "use this type".

...Use Denso it20's for the plugs.
...I may change the plugs to those recommended as well as I have experienced in other cars not being happy with other types of plugs...
They run better in a mzr motor then the Motorcraft ones.
Hello, Felix,... Please do not recommend those plugs without a brief discussion about the many-other & more common spark plug options. Let us please not OR please do bring-up the crazy spark plug sticky. Uhg.

Many-many FF D2/D2.3 owners use Autolite A103's in that engine, and I think we should acknowledge this, especially when talking with a new FF member -like the OP.

This is not an argument about spark plug types you prefer or that I prefer. This is only a reminder that any new OP should (briefly) hear about the many options; and we should let them know about the "personal poison" options out there.

A103 Copper plugs are a very good plug, -and commonly used, for that engine. Other longer lasting plugs (Platinum & Iridium) should be considered too. -At the car owners discretion, and personal preference.

I am currently running AR103's, just for the fun of it, -and as a test. No pro's or con's have been found with these AR's.
 
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