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Old 04-07-2013, 03:33 PM   #1
timbowabo
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Possible IAC problem after engine swap.

We just finished a 2.3 engine exchange in a 2004 Focus.

It runs good, but the idle is too high. On flat ground between 18 and 30 mph the car actually gains speed without touching the gas pedal.

This is our 3rd engine and I'm pretty sure the vacuum lines are all OK, except one on the top front of the engine that has been purposely clogged off. I was told by Ford dealer that it's an emission control and shouldn't affect performance.

We unplugged the IAC and the car runs nearly perfect. I'm tempted to leave it like this out of frustration, but would much rather figure out the real problem.

There are no codes, except the unplugged IAC.

We put the old IAC on it, but it didn't help. I bought a new one (which has been returned) and it made it worse. I did not unhook the battery which I've read resets the computer. I'm wondering if I should try again.

The dealer charged me $100 and his advice was, "If it was my car, I wouldn't mess with it."


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Old 04-08-2013, 05:12 PM   #2
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Originally Posted by timbowabo View Post
I did not unhook the battery which I've read resets the computer. I'm wondering if I should try again.
I would definitely give that a shot. If you want: I can go plug back in (only) my lower O2 sensor, and show you what the vehicle does when given gas (3 second delay on the pedal).
The computer learns real easy, and real fast. IIRC, after it's "learned": It doesn't RE-LEARN on it's own to accommodate any changes (different IAC that actually works).

If nothing else: You can just clean the IAC you have (assuming that's what is causing the issue with it not shutting fully).
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Old 04-08-2013, 05:48 PM   #3
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Why does this guy have 126 views and only 1 response? Knowledgeable people are doing too much lurking or moderating.

I agree with Oblivion, unhook the battery and let the ECU/PCM relearn some things, it can't hurt and it's easy. Did you change the PCM with the engine swap? If you've done a few of them you know more than I do, I would guess a PCM swap would also be prudent if not necessary. If you didn't put in a PCM for a 2.3, the 2.3 is trying to run on learned data about the previous 2.0 and that might not match up well. IAC malfunctions are pretty much always mechanical in nature, the PCM instructs it to a set position but the IAC is mechanically sticking, if the PCM hasn't learned that it needs a new base idle position it will rely on the old data and give an off idle. I'd think a 2.3 ingests a little more air at idle than the 2.0 and could result in a lower idle so that's kind of counterintuitive to the high idle you're experiencing, that's the counter argument to the PCM reset and it's worth considering.

You might also let the car idle for 5 minutes or more all by itself with no interruption, apparently target idle is learned and set after that timeframe.
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Old 04-08-2013, 06:37 PM   #4
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You might also let the car idle for 5 minutes or more all by itself with no interruption, apparently target idle is learned and set after that timeframe.
Yea.. Warm up the engine (drive around for a bit), then disconnect it for the ~15 minute period, then hook it back up while it's still warm, and let it idle.
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Old 04-09-2013, 07:33 AM   #5
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Thanks for jumping in guys.

Before the thread goes too far astray I need to clarify that this was a straight 2.3 to 2.3 swap. I dabbled with the idea of going 2.3 to 2.0 on previous threads, but ended up finding an exact match.

We're going to work on the car today, and I'll try your suggestions listed above. Thanks!
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Old 04-10-2013, 10:27 PM   #6
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The car finally gave me a code. Intake manifold runner control idle air intake shutoff. It was the part that had the air port purposely clogged. I bought it, replaced it, didn't help.

Now as far as I can tell, everything on the car is correct. Bad parts replaced, vacuum lines in place, no codes.

The persistent problem is that it maintains speed without touching the gas pedal.

For instance, I will be running around 35 mph and take my foot off the gas. The car will slowly drop speed until 29 and stay there for 3/4 of a mile or so. It sometimes will start to drop again and will settle at 24 or 21 and stay there. It also does it at slow speeds of 5 mph or so.

It has a new throttle cable, new cruise control cable, the IAC has been cleaned and switched out, throttle body has been cleaned and switched. Fuel filter was changed shortly before the engine swap.

The car runs basically good and has good power, but it feels somewhat dangerous since it goes whatever speed it wants to, and it's surely wasting gas, and is hard on the brakes.

We did the battery disconnect too btw.

I'm considering having the computer reprogrammed (flashed or whatever the correct term is.)
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Old 04-10-2013, 11:25 PM   #7
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Quote:
Originally Posted by timbowabo View Post
The car finally gave me a code. Intake manifold runner control idle air intake shutoff. It was the part that had the air port purposely clogged. I bought it, replaced it, didn't help.

Now as far as I can tell, everything on the car is correct. Bad parts replaced, vacuum lines in place, no codes.

The persistent problem is that it maintains speed without touching the gas pedal.

For instance, I will be running around 35 mph and take my foot off the gas. The car will slowly drop speed until 29 and stay there for 3/4 of a mile or so. It sometimes will start to drop again and will settle at 24 or 21 and stay there. It also does it at slow speeds of 5 mph or so.

It has a new throttle cable, new cruise control cable, the IAC has been cleaned and switched out, throttle body has been cleaned and switched. Fuel filter was changed shortly before the engine swap.

The car runs basically good and has good power, but it feels somewhat dangerous since it goes whatever speed it wants to, and it's surely wasting gas, and is hard on the brakes.

We did the battery disconnect too btw.

I'm considering having the computer reprogrammed (flashed or whatever the correct term is.)
Mechanically? I have no idea what would be causing it to run like that then. The throttle body, idle air control valve, and one other part I think? are the only mechanical parts that control the air (more air + fuel vapor + spark = faster car).

Electronically? It could be any number of things! You will either have to wait until someone with much more experience than myself can help, or actually (this part makes me shudder) pay someone to look into it.

Obviously I'm not there. So I can't physically diagnose it, or test anything. The only other thing that would come to mind is if the clutch isn't letting go... but that wouldn't make sense. Because if the engine is at an "idling speed" and the clutch is connected still: The car would pull forward slowly. That's it!

Also, this is unrelated, and I think you drive a 2005, and the other guy a 2004? But, what was the part number?

- http://www.focusfanatics.com/forum/s...58#post4678958
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Originally Posted by Squishy Crayons View Post
Is there anywhere I can find a part number or actual part for IMRC Solenoid?
This person wanted to know. Maybe you two could help each other out somewhat?
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Old 04-14-2013, 10:14 AM   #8
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I'm still trying to work this problem out.

I tried dropping it into neutral while driving down the road (while it was stuck at a certain speed). The idle remains too high until it comes to a stop.

I notice this too when I stop normally in gear. I feel the car downshift into 1st, then it almost feels like another downshift when the idle returns to normal.

Suggestions? I'll try anything at this point.
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