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Topic Review (Newest First)
07-31-2016 11:50 PM
fin reaper Rycodge - did you ever figure this out? Defective new IAC?
07-17-2015 05:01 PM
amc49 No sense in posting if you do not even mention the problem. You could have messed up there even while supposedly fixing it. Now you have no cruise, another problem.
07-17-2015 02:20 PM
duncanidahoe Not sure about the iac, but fix the problem I disconnected the cruise control problem fixed!
01-18-2013 11:04 PM
rycodge So I disconnected my new iac valve tonight and low and beyold the damn car idles like you would expect!
Does this mean the replacement iac is faulty?? I'm slightly confused but I'm assuming the cheap autozone part was d.o.a....
01-18-2013 04:47 PM
rycodge I'm sitting here at work almost starting to worry about a cracked intake manifold.

Here's why it *could* be cracked.

1. Car is a salvage title with front passenger side impact
2. Engine just sounds "loud" from the interior (new motor mount helped a lot, but this engine is still LOUD anywhere above idle when I compare it to my 2001 GTI 1.8T)
3. Vacuum hoses look great, but I can't get my idle under control.

I'm going to try unplugging the IAC valve tonight to see how it behaves at idle.

Are there any common places where the zetec intake manifolds would crack?

Any help is greatly appreciated
01-18-2013 02:49 PM
rycodge So I've replaced the IAC with a new valve. After cleaning up the old one, the plunger was very stiff to move and hooking up the old IAC to a 9V to actuate the plunger didn't do the trick. I later stepped up to 12v 2amp current from the battery charger to test and no dice.

Problem is the car is still idling very high between shifts and it only calms down when the car is not moving for about 10 seconds. I disconnected the TPS just to see and the car was exhibiting the exact same problems. No CEL code though??

One interesting thing the car was is doing after replacing the IAC valve is somtimes the car will WANT to fall down to like 1000 rpm when I depress the clutch and it will "bounce" between 1000-2000 RPM a few times, then stay up around 2200 until I come to a complete stop. It doesn't always do this, but it seemed to be 1/10 times I depressed the clutch while driving down the road.

How does the engine even calculate the proper throttle response when the TPS is disconnected? Does it use the O2 sensor and MAF to guess what the air / fuel should be?

Do you think I may have replaced my bad IAC valve with a defective valve?

Any other sensors that could be causing this? I've tried two different tps's.

Maintenance I've done to the engine so far:

New crank sensor
New pre-cat O2 sensor
New passenger motor mount
New air filter
New spark plugs + wires + coil pack
New PCV valve - vacuum line looks good.

This is the last engine issue I'm trying to sort out! It's driving me mad lol.
01-16-2013 05:25 PM
Mile30 Start with the sensor, though. It waaaay cheaper!
01-16-2013 05:24 PM
Mile30 One guy rotated the sensor as other guy "drove on the dyno". They both were checking the input signal and when it became visibly smoother in the scope; they tightened it up right there. I haven't had to touch it since... I avoid touching it now when working around it because the whole process was such a pain.

I bought and went through 6 tps sensors before the dyno appointment. That was a rather expensive day, but the car's run great ever since.
01-16-2013 05:07 PM
rycodge That makes sense. I must have the late 03. The new tps was identical to my old one. My old one appears to be working just fine.

I think I only rotated the sensor about 20 degrees or 3/16ths of an inch to line up with the screw holes on the throttle body.

How did that shop permanently "adjust" your tps?
01-16-2013 05:07 PM
Mile30 Oops!
When I unplug the battery... the adaptive learning resets and it takes a month of regular driving for the idle to come back down to normal. It's a bit annoying, and I always remember that after I unplug the battery to work on it again.
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