Bad idle when cold

[tuffy65]

IN responce to replacing the idle air motor it now doesn't die or have the rough idle all the time. now it's just when cold.What could be causing this? once it warms up runs and idles ldles like a dream.

[tuffy65]

Any body even care to wager a guess?

[phil-l]

Quick thoughts:

- Is the check engine light coming on? If so, do you know what codes are being thrown?

- Idle problems can result from vacuum leaks. Yes, there are vacuum leaks that can be temperature sensitive. What model year is your Windstar? Several years (including my '00) are subject to the infamous isolator bolt leak problem, which can cause a number of issues. Here's a nice write-up on this topic:

http://www.leckemby.net/windstar/windstar01.html

I did this fix a number of years ago; it worked fine for me.

[tuffy65]

Yes check engine light is on but do to being 3 bad 02 sensors. the year is 01.

[phil-l]

What are the actual error codes?

In my experience, OBDII codes that point to oxygen sensor failure are often caused by things *other* than oxygen sensor failures. Vacuum leaks are a common item that can throw O2-related codes.

I believe the '01 3.8 Windstar is affected by the isolator bolt fix.

Review this video for Windstar vacuum leak concerns - and the isolator bolt fix.

[12Ounce]

There is a IAT (inlet air temp) sensor ... actually the IAT is part of the inlet Mass Air Flow Sensor on some engines .... and also a ECT (engine coolant sensor) that might be playing a role here.

[tuffy65]

I was kinda wondering that my self. can you tell me where it is located? thanks.

[phil-l]

If memory and quick Googling don't fail me...

I'm pretty sure the IAT is integrated into the MAF for this engine.

The ECT is - as I recall - basically below the throttle body. Yes, you have to remove a few things to access it, but it isn't really that bad.

[12Ounce]

Yes, those locations are correct I believe. I would bet on the ECT having failed first of the two. The MAF sensor elements can be sometimes recovered by cleaning with alcohol moistened cotton swabs ... but one must be super-cafeful! This sensor package is located in rubber flex air intake horn between air filter and throttle body.

[tuffy65]

They list both parts separate. but i'll be damn if I can find either one. it's also cold out and I didn't speed much time either.thanks for all your help so far.What I mean is they sell both the IATand ECT separately

[tomj76]

Not to be a smart-alec about it, but the sensors can often be found by tracing the wires and knowing what part of the engine to look at.

For example, the Intake Air Temperature sensor in going to be between the throttle body (which has the throttle cables attached) and the air filter. It has wires attached to it, so that will narrow it down. My '96 has two devices like that, one is the MAF sensor which is located in the downstream half of the plastic housing that holds the air filter, the other one is in the bellows between the air cleaner housing and the throttle body, which is attached to the intake manifold.

In my '96, the first one is the MAF and the second one is the IAT (they are separate on the '96 3.8L engine). Like 12Oz said, the MAF is serviceable, but also fragile. It has fine wires (one hot, one cold) that are used to indirectly measure the amount of air flowing through the intake. Sometimes those wires can get dirty and a solvent cleaner (MAF cleaner) can be used to restore the MAF. If the MAF is dirty, it reads less air entering the engine than is actually occurring, and the computer has conflicting data between the oxygen sensors and the MAF (too much O2 exiting the engine for the amount of fuel, which can appear like a vacuum leak).

On the other hand, the IAT uses a thermistor (a temperature variable electrical resistor) covered in plastic to sense the intake air temperature. It doesn't matter much if it is perfectly clean like the MAF does, so it less likely to benefit from cleaning. However, a bad IAT contributes to improper amount of fuel since the PCM calculates the amount of fuel based on the reading.

Here's a picture:
http://www.berrysweb.com/images/Autos/CleanMAF/MAF1.jpg