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Discussion Starter #1
I have the 98' Duratec and for the past month I have no power on take off. After numerous trips to the stealership they can't diagnose a problem. After many days of troubleshooting and observation, this problem only happens on hot days (AC on) when the outside temp is above 85. In stop and go traffic I can accelerate moderately and once the car shifts to 2nd (auto) there seems to be no power. The RPM's stays steady (i.e. on 2000) although I'm pressing down harder on the accelerator. Also, the car surges as it is trying to pick up speed. It will finally take off after some hesitation. If I floor it, the car takes off like a jet. There are no other problems. Idles fine, runs great at highway speeds. However, it seems that my MPG drops drastically when this is happening. I'm stumped!!
 

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Originally posted by Tazbear@May 24 2004, 10:03 AM
hot days (AC on) when the outside temp is above 85.
There's your problem. The AC compressor runs directly off a serpentine drive belt. When the AC is on, it takes a ton of power from the engine, hence the hesitation and lack of performance. Additionally, when the AC is on, since the engine must power the AC as well as the drive wheels, it decreases your MPG. Think of it as a situation where you're basically driving with your parking brake engaged partway. You can still drive relatively well, but you lose performance and overall efficiency.

JR
 

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Discussion Starter #3
You're right about the AC and I understand the concept but this is more than a "drag" on the engine. I've driven the car many years with the AC on and what I'm experiencing now is a very BAD hesitation issue. I've had cars behind me blow their horns or fly from behind me because I can't get out of their way fast enough as my car is basically just creeping along. I should have mentioned that I turn the AC off sometimes when I'm experiencing the hesitation and there is no significant difference in power gain. I'm wondering if it may be a sensor. I cleaned the MAP with elec. cleaner and replaced the cam shaft posit. sensor but no change. Could it be the coolant temp. sensor?
 

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Tazbear- I had the exact same problem on my 98 duratec. It is caused by the IAT (Intake Air Temperature) sensor. It is exposed to too much engine heat in our cars. On hot days it will give grossly exaggerated temperature readings to the CPU causing it to retard timing, thus the sluggish response in hot weather. I measured temperature readings from the IAT as much as 15 F above the actual outside temperature.
I have compensated mine for this problem by inserting a resistor in line with the IAT. This has worked wonders for my car. I couldn't believe the difference.
And yes, this is essentially the same procedure as the controversial IAT-mod. But mine is done for a good reason. It brings the IAT readings to accurate levels during the summer heat. I have veryfied that several times.
If you need specifics, let me know.
 

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Yes, it is located on top of the air filter box. The part that's sticking out with the cable attached to it is the one that heats up considerably, passing on some of that heat to the actual sensor inside the filter box. I have removed the sensor from the filter housing on hot days after driving for awhile, and I almost burned my fingers just touching the outside of it.
If you want to try the resistor, get a 4.6K Ohm resistor from Radio Shack. and splice it in line with one of the cables going to the IAT sensor.
It is important to keep the sensor and not just replace it with the resistor as is suggested by some internet sites. You want to still have a curve that reflects changes in the intake air temperature. Splicing the resistor in line will simply lower that temperature curve by a number of degrees fahrenheit to reflect the true intake air temperature.
 

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Discussion Starter #8
Deniz, thanks a heap! Heading out now to get parts and try it. Will let you know once I have a verdict.
 

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I would recommend a CAI over modding the IAT sensor. The IAT sensor may be picking up extra heat, but it's not an entirely false reading. A good portion of that heat soaks into the intake, especially in stop and go traffic.
 

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Correction: Make that 4.7 Kilo Ohms, not 4.6. Not that it would make a difference, but you won't find 4.6K...4.7K ohms is a standard resistor value.
 

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SixFoFalcon-
yeah, a cai would be another choice, but it will cost you and depending on where you live can leave your engine hydrolocked.
The only other alternative to the IAT compensation would be to simply relocate the IAT sensor into the fender well, assuming one has not removed the resonator yet. Otherwise there's really no place to expose the IAT to intake air and not have it inside the engine bay.

I know a lot of people cringe at the idea of changing an engine sensor's output by a simple means such as a resistor. All I can say is that I have had great success with it. The bull (duratec) used to get so sluggish during the summer months here in Florida that it felt as if I was missing two cylinders. It felt like a 120 hp engine at times, it was that bad, despite timely tune-ups.
With the resistor those problems have completely disappeared, and although I am using regular, I do not experience pinging.
 

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Discussion Starter #13
Deniz, how did you splice in your resistor? Did you use a pigtail clamp or cut and tape the wires together?
 

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Wow, I'm almost tempted to try this. I noticed this issue with my Duratec also. My 94' Ranger used to do the same thing.

I think he just put it in-line on one of the 2 wires (in series with the IAT not in parellel). Let us know if it works on yours too. If it does, I'm gonna have to whip out my resistors from college and try and remember the resistor color code. OH NO! :eek:
 

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I have a huge cone filter in the fenderwell and I don't worry about water ingestion. Some have the inlet up by the front grill and this is a problem. I had it there at first but decided against it. If I got water ingestion now the water would be over the door sills.
 

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Let me make sure I am remembering the color codes right.

Yellow, Violet, Red = 4.7K Ohm?
 

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Discussion Starter #19
Deniz, got resistor and a new IAT sensor. I'm still a little confused about how to splice in. I can't tell from pic what kind of connector you used. Guy at radio shack said to solder it on but I don't think that would be wise. Can I just cut the wire and insert the needle like end of the resistor into the insulation and tape it or would that not make a good connection? Drop me a line when you can! Thanks again!
 
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