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1993 Ford Tempo Idles fast 2500 RPM

Tiny
JSMERDEL
  • MEMBER
  • 1993 FORD TEMPO
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 60,000 MILES
I have a 93 Ford Tempo and it is idling at 2500 rpm. I have checked the TPS and it is.9v at idle, I used a three lead pot and set the voltage to.4v and that didn't help.
I removed the IAC and watched it move up and down, seems ok. I even replaced it with a unit from AutoZone and it made no difference. I can unplug the IAC and there is no affect. I coonect a tester to the IAC and was able to open it and close it. If I squeeze the hose that goes to the IAC value I can bring the idle back to normal. I don't hear any other vaccum leaks. I'm wondering if I should have cleared the PCM when I tried the new IAC value from Autozone, I didn't do this step. Any ideas.

Thanks.
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Saturday, September 26th, 2009 AT 8:49 PM

14 Replies

Tiny
FIXITMR
  • MECHANIC
  • 9,990 POSTS
When did the problem start? Was it sudden? Did you check that your throttle butterfly is completely shut? Put a piece of cardboard to block opening completely and see if idle goes down. What air hose does does IAC have? I have a 92 and there is no air hose. You could have tested for bad IAC by removing and blocking holes with cardboard! That hose you pinched seems to be related. Where does it go?
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Saturday, September 26th, 2009 AT 10:56 PM
Tiny
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Hello, it started a month or so ago. The hose runs from before the throttle plate to the IAC valve. It is the air by-pass. If I remove the IAC and plug the holes the engine will idle slow and then die. I know it sounds like a bad IAC, but I did test it and I can see it working. I also tried replacing it with a new one from Autozone, it wasn't exactly the same but there was no change in the idle speed. I can also control the IAC using an OTC 4000 and there is no change in the idle speed. It is like the valve is being sucked open by the vaccum in the intake manifold. I can push the valve open with a screw driver, so enough vaccum might also pull it open. When I squeeze the hose which goes to the IAC valve I can bring the engine back to idle speed and you can here the IAC valve working as I make it go too slow or too fast.
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Saturday, September 26th, 2009 AT 11:09 PM
Tiny
FIXITMR
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Is this your car? Put a restrictor in the hose to achieve proper idle? Just a possible quick temp/perm fix?
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Sunday, September 27th, 2009 AT 3:42 AM
Tiny
JSMERDEL
  • MEMBER
  • 9 POSTS
Ok, I did this today, I made a gasket with smaller holes for the intake air and output to the intake manifold. This brings the idle speed down to 800 in netural, about 750 in drive. However, when the A/C or P/S is activated the idle will drop a bit.

If I only new if a new replacement valve sealed completely, then I would know mine is bad. I can blow through mine when it is removed from the engine, It is not wide open, it looks like it is closed, but it is either leaking or doesn't seal completely.

I also can block off the holes and control the idle with the idle linkage set screw.

I think the IAC I tried from Autozone goes in upside down from the valve I have, I didn't look at the instruction, wish I had. I saw a picture of the valve on the internet and it shows the input and output are oppsite from the valve I currently have. When I tried it I put it in the same way my current valve is, so maybe it wasn't a valid test.
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Sunday, September 27th, 2009 AT 7:39 PM
Tiny
FIXITMR
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Actually, you cant use the throttle plate adjust screw to set idle because the butterfly will then not completely close and cause the car to 'deisel' when you shut it off. I know cause I went that route before. I've never actually studied an IAC that closely to see how it works. Iv'e heard of them becoming dirty/sticky but that's about it. Maybe the problem is related to the computers sensing of the rpms of crank? Dont know what part/sensor is responsible for that function though. I also have no experience with a IAC with a hose. I do happen to have a tempo that my grdaughter drives and is out of town that is/was having idle problems that would come and go but I never have gotten around to fixing it although she wore out a set of break shoes/rotor because of it! That car is a 92.
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Monday, September 28th, 2009 AT 1:13 AM
Tiny
JSMERDEL
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At this point I ordered an exact replacment IAC online, I have my fingers crossed that it will cure the idle problem.
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Monday, September 28th, 2009 AT 7:07 PM
Tiny
JSMERDEL
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I received the new IAC on Friday and installed it today Sunday 10/04/09. This fixed the idling problem completely. The previous one I tried from Autozone had the same fast idle poblem, but as I mentioned it also looked different then the one that was in the car.

Can anyone tell me where their temperature gauge sits when the car has warmed up and idling. On this car the temperature gauge points to the 'A" on the word NORMAL when the temperature reading is 195 degrees from the ECT sensor.

The fan will come on around 213 degrees and cools the engine down to around 209 then turns off. I would think the engine would cool down to below 195, but this is not the case.

I thinking that the thermostat my not be opening all the way.
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Sunday, October 4th, 2009 AT 4:56 PM
Tiny
FIXITMR
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Do you have an infrared temp reader? They sell them at harbor freight pretty cheap. You can check temps all over engine and hoses and radiator. All the tempos i've owned show about r or m lettter when warmed up. And the fans come on much sooner according to gauge temp. Berfore red is reached. You could have a blocked dirty radiator/fins?You can try washing with waterhose aimed from front. As long as water bottle dont bubble/hiss/steam you are probably ok. Do you have air cond and use it? This can account for higher temps.
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Friday, October 9th, 2009 AT 11:17 PM
Tiny
JSMERDEL
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I have an Infra Red gun and the temp is ok at the thermostat housing and upper radiator hose. The overflow bottle doesn't bubble, or hiss. I did remove the radiator cap and the temperature of the fluid was only around 100 degrees. I'm thinking the thermostat is not opening all the way. I won't have time to get back to it until weekend after next, but I think I'm going to remove the thermostat and see if that fixes it.
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Friday, October 9th, 2009 AT 11:38 PM
Tiny
JSMERDEL
  • MEMBER
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I had some time today, so I decided to remove the thermostat and see if that cured the heating issue. I did not have to look any further. The thermostat was in two pieces. I picked up a new thermostat at Kragen and a gasket at Autozone and put it back together. The radiator fluid, upper and lower hose are now all at the same temperature. The temp gauge now reads between the R and M in the work NORMAL. Driving it around with normal stops, it will stay closer to te 'R'.
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Sunday, October 11th, 2009 AT 11:29 PM
Tiny
FIXITMR
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Sounds like things are AOK now? But it's a ford, so never let yer guard down!
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Tuesday, October 13th, 2009 AT 3:34 PM
Tiny
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Here is a picture of the bad Thermostat


https://www.2carpros.com/forum/automotive_pictures/414257_tempoPic2sm_2.jpg

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Tuesday, October 13th, 2009 AT 3:42 PM
Tiny
FIXITMR
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Cant say i've ever come across 1 like that. Maybe the car went without antifreeze for a time? Of course if it's original then time is certainly a factor for corrosive effects.
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Thursday, October 15th, 2009 AT 11:39 PM
Tiny
JSMERDEL
  • MEMBER
  • 9 POSTS
Well, I'm a chevy guy, this was actually my daughter in-laws grandmothers car. Can't stand the seat belt the belts you in automatically, almost got my arm when I was reaching in to turn on the engine.

It has a by-pass hose, not sure if it goes to the heater or the water pump, but it isn't controlled by the thermostat. Guess it would be the heater hose.
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Friday, October 16th, 2009 AT 10:07 AM

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