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rycodge 01-16-2013 04:24 PM

Very High Idle - Throttle Body and TPS sensor questions
Car specs: 2003 ZX3 with zetec 2.0 and 5 speed manual.

Hi all. I recently purchased a focus and I've been going through a bunch of small maintenance items. Before I tell you anything I will be cleaning out my IAC valve and installing it with a new gasket tonight! [thumbd] BUT, I'm a bit confused about the TPS on my zx3.

I went to autozone and asked for a new TPS. Apparently the manual and automatic have different ones with slightly different harness connections. I originally purchased the manual tps only to discover my car has the automatic one even though I have a manual tranny?? Is this normal? Is this a 2003 thing?

Also, I noticed when installing the TPS I have to sort of load up the sensor (turning it slightly) to mount it on the throttle body. For those of you that have replaced this, is this normal?? My car is idling very high (2k-3k) with both my original tps and the new tps. I was wondering if I might have the wrong throttle body on my focus (sometimes you never know what the moronic previous owners have done [nono]).

Thanks in advance!

zetecDon 01-16-2013 04:35 PM

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Mile30 01-16-2013 04:51 PM

Your 'Julian date' is really important for ordering parts; don't specify clearly enough, and you're going to do a lot more driving and waiting for parts and returns!

I have a late-year '03, and the throttle body is different than the cars made the day before the change-over... in other words; after July you got a "revised" bracket for the cables and TB. I needed to go to a capable shop with a dyno; they ended up using an oscilloscope function (or yourself on a high-end scan tool)...

You may not need to do that; but the fact that you have to load-up the potentiometer to make it function... I think you may need to check your VIN carefully and reexamine the part numbers. There should be contact with the throttle body pivot pin, but not an excessive amount of twist to line everything up. The gents that dyno tuned the car left the machine screws tight enough to stay put, but loose enough to wiggle... somewhere, while sloooooowy rotating the tps sensor millimeters; the throttle input signal smoothed out and the idle settled nicely after that. What they did isn't something you can do in the driveway unless you got the tools and the chops, though. Easy answer is early/late model year part issue.

When I unplug my battery the

Mile30 01-16-2013 05:07 PM

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.

rycodge 01-16-2013 05:07 PM

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?

Mile30 01-16-2013 05:24 PM

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.

Mile30 01-16-2013 05:25 PM

Start with the sensor, though. It waaaay cheaper!

rycodge 01-18-2013 02:49 PM

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.

rycodge 01-18-2013 04:47 PM

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 [ffrocks]

rycodge 01-18-2013 11:04 PM

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....

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