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post #1 of 6 (permalink) Old 08-24-2016, 11:29 PM Thread Starter
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Could it be IAC

Hello all

95 Tbird 4.6 200000 Miles.

Had the code for EGR excessive flow, blocked off the EGR. Fuel trims correct now, and ran great until this evening.

I started it up and it had a pretty bad miss at 1200 rpm until it warmed up and idled at 750 while in park.

As I drove it, it kept having that miss under light acceleration. It had this before but when I blocked off the EGR it went away, but now that its back I guess it was not the EGR. Has new plugs and wires, and coils look they have been changed.

I have the 95 thats apparently hard to get to the IAC, thoughts or ideas?

No additional codes or anything either, and all fuel trims are within +-3%, except at idle LTFT B2 reads +14% but as soon as I touch the throttle it goes to around 3%.
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post #2 of 6 (permalink) Old 08-25-2016, 09:24 AM
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Admittedly, I had the intake manifold off the car when I took of the IAC to clean in there, but it didn't seem like it would be a disaster to R&R it while on the car. It's just tucked down in there a little on the driver's side.

When I used to have the code for excessive EGR flow on my old 95, the car ran fine, and even got better gas mileage! A bigger problem at 200k is the EGR tube being clogged, of which there is no replacement, nor can it be cleaned on the car. I had four days of soaking that tube with heavy duty stuff to prove that! It is caused by leaky valve stem seals and high oil consumption.

Al

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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post #3 of 6 (permalink) Old 08-25-2016, 10:47 AM Thread Starter
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THanks Al,

Is the IAC more on the bank 2 side of the manifold?

If so, this would definately be causing my +14% LTFT Bank 2 reading at idle only, as I understand the iac closes when throttle is in operation
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post #4 of 6 (permalink) Old 08-25-2016, 12:22 PM
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On my Toyota, the IAC is open any time the car is in vacuum, obviously to a lesser degree as vacuum decreases. But that is a different setup altogether.

I doubt the Ford IAC suddenly closes all the way just because the throttle is open. When you are coasting, it has to be open or the car would stall. I would venture to guess the IAC opening varies by vacuum just like my Toyota, only fully closing when vacuum is "0".

Al

97 T-Bird LX 4.6 - 80k miles
94 Supra TT Auto - street/strip car
04 CVPI- Brenda's car - 76k miles
Previous Fords:
95 T-Bird LX 4.6 - fully optioned, owned 15 years, 220k miles
96 Cougar XR-7 4.6- Brenda's car, owned 11 years, 187k miles
88 T-Bird 3.8 - first T-Bird, owned 5 years, 206k miles
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post #5 of 6 (permalink) Old 08-26-2016, 05:47 PM
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Quote:
Originally Posted by Pearcetopher View Post
If so, this would definately be causing my +14% LTFT Bank 2 reading at idle only, as I understand the iac closes when throttle is in operation
For what I've observed, it doesn't close when throttle is applied. I have a part time IAC failure now. While driving the engine loses some torque and drops rpm when IAC goes down. All normal again when IAC wakes up. So, I assume IAC is supposed to be open.
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post #6 of 6 (permalink) Old 08-28-2016, 02:10 PM Thread Starter
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Interestingly,

After a removal, carb clean, then a good lubing with moovit, it seems to operate much better.

Also, I was expecting the IAC on a 95 4.6 to be just as bad of a nightmare as the EGR however it only took 5 mins to remove.
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