X-Jester

Take the car to the dealer and get it scanned. I've seen many people with the hesitation wind up having a leaking injector. I say, bite the bullet and find out exactly what's wrong.. If my new opti (my original had 94k on it) doesn't fix my awful hesitation problem, that's where I'm going, too.

Bryan

Fastbird93

Autozone is feeding you junk. I have two 93's and BOTH have IAT's. I'm pretty sure that a 94-97 will plug right in, but don't quote me on that. If anything, head to the dealer. I'm sure that the premium won't be that much more than Autozone.

Carlos01SS

Check this out, I did go to the dealer, & for the 93, they told me that it's not sold separately, I would have to buy a new intake elbow...???

Maybe I'll ask for a 94, IAT, see what happens?

SiDeWaYZz28

i had the exact same problem but i changed the plugsand wires now its runnin so much stronger

ChickenScreamer94

Well, bad news, my new little fix crapped out on me five days later. Oh well. I really think this is a heat related problem. Hopefully i will find it. Oh yeah, i really doubt it is the injectors. I think they would be more consistent with this problem and give me hard starts, right? I may pull the rail but i dont think they would do this.

MentalCaseOne

I wouldnt be so heisty as to look for the problem somewhere else just yet. You said it fixed the problem for five days. It just occured to me that if the IAT with by the way is NOT a switch as someone mentioned earlier, may get dammaged by excessive voltage applied to it... check your pcm voltage.

Marvin

ChickenScreamer94

actually, i think that the IAT is getting damaged by the heat, but i couldnt say that since it should have done this since the car was new. How do you check the voltage to the IAT?

Transamdriver

*HINT* AutoRice and Rice Boys workers generally dont know jack.

There are the always the few who break that rule, but the majority are retards here where I live.

Seabat

I have almost 2 weeks driving on the new IAT, still no stumble. Keeping fingers crossed that the fix lasts. Getting ready to put it to bed for the winter, now that it's running right I may do some mods.
Just for info, on the 93 the GM parts list does not show the IAT as a seperate part, refers to the intake elbow assembly. This is the same number as later models. If you need an IAT for a 93, ask for one for a 94. Seems that this is carried over to the parts list at Autozone etc. etc.


93 M6 Red 59K
Off road pipe, EGR, TBB, B&M Shifter.

MentalCaseOne

If you dont mind waiting a little bit I will wait for my car to completely cool off (necesary step)


The first measurements with engine cold @ ambient temp.

I will disconect my IAT and measure the voltage applied to the contact leads, Key on ignition engine off. I dont know but I am guessing it should be 5 volts.

Next I will plug the IAT back in and will take the same reading at ambien temp with engine off

Next step I will read the voltage with the IAT conected and engine operating at 160* degree.


This will provide you with 3 readings.


The voltage applied to the IAT by the PCM.
The voltage drop once the IAT is conected

and finally the Voltage reading while the engine operating at 160 degree farenheith.


Why all this readings?? The PCM applies a carefully measured voltage/intensity to the IAT. The IAT is a Thermistor... it works by reducing its resistance as it gets hotter. So to make it simple, when the engine is colder the voltage accros the conector leads should be higher than when its hot. These are very delicate measurements and any slight difference may mean a lot to the PCM.


Acording the Shoebox's (a member of this board) and the Chiltons Book the IAT should have the same or very close to resistance to the Coolant temperature sensor. I have precisely measured a brand new one and I have a long list of resistance readings for just about every degree from 40 farenheight to 208 farenheit. I will match my IAT to see if still in perfect condition or not.... it may be off by a little but my car is operating in top shape right now...


Why is this important?? Some Thermistors develop a very peculiar problem... the work just fine at some temperatures and go bad at others. For what I know it has to do with Heat expansion and stress.... A good IAT should show have its readings predictable... the same rate of resistance change per rate of temperature change.

In electronics I have observed damaged Thermistors that after heated they either went into open circuit once they reached a certain temp... just to read fine once the temp dropped down a little and other intermitent problems...

Why voltage is important?? Because the voltage applied by the PCM should change with diff temps of the IAT. if it doesnt or if it is too high it will immediatelly tell me that either the IAT is bad or the PCM is bad....


In your case if your IAT keeps blowing up (per say) Then I will start suspecting the PCM maybe damaged and its sending the full 13.8 volts to the IAT and damaging it.

Any way its too early for me to tell. Your IAT is made to handle the heat at its OEM location so that should not be a concern.


My car is just park outside but I came back home about 2hrs ago I am sure its not cold enough just yet..

Marvin

MentalCaseOne

For you guys who are electronically inclined....

In regards of the IAT readings... If the PCM works like all the Temp sensors I have encountered... then it just applies a current source and then it measures the voltage variations...

As soon as I get my hands on a pair of small enough alligators I will read the milliamps supplied by the PCM. It they do not change with temp changes then we will be able to predict any and all voltages across the IAT conection leads at any temperatures then create a baseline and we culd tell a problem at the IAT by just comparing the results of our cars to the Baseline. I know its only gunna work with cars that use the same type of PCM and same IAT number but hell I am game if you guys are.......


If I am right I will be able to help you guys save a ton load of money. As it is right now what I see is that most people go through changin part after part hoping they hit the jackpot. This should not be the way. Little by little we can crack the code here and find consistent ways to read our sensors.

Shoebox if you could get any info as for what voltage and what amps/milliamps the PCM is supposed to supply to the sensors I could just create a baseline voltage/temp readings that you could post in your website.

is that feasible?? (forgive my typos)

I hope I can help you guys out.


Marvin

SinisterSS

From the Helm manual for my '96...

IAT
100,000 ohms @ -40 deg F
70 ohms @ 266 deg F

The PCM supplies a 5.0 V signal to the IAT and measures the voltage. Voltage will be high when the air is cold, low when the air is hot. The PCM uses this to adjust spark timing according to incoming air density.

On OBDII cars, the following codes will be set with a faulty IAT:

DTC P0112 circuit low
DTC P0113 circuit high
DTC P1111 circuit intermittent high
DTC P1112 circuit intermittent low

Data logging my car with EFILiveV5pro, my car measured the IAT at "84" (don't know what units) which EFILive scaled to 111 deg F. Also had a reading of "68" which scaled to 82.4 deg F. And finally, a third reading of "67" which scaled to 80.6 deg F.

Stormman

What's interesting about that is when I get new 1LE elbows from Jason Cromer, the IAT comes with it, also called duct ***'y for my 94. If you order the IAT from him its like $9.00. But you should be able to get it anywhere they are the same for all LT1's I believe. So like eveyone says ask for a 94 or 95 whatever.

MentalCaseOne

Using your values and the Chiltons book values

I found a difference between 7 and 13percent across the band
with the Chiltons value consistently lower than yours..


I am just gunna go take my IAT off and read its temp with an infrared meter while I read its resistance and see what happens.

Its only a preliminary test though since my IAT has 140k miles on it. My car is running very good right now so I guess its a starting point till I get a brand new one.


Marvin.

MentalCaseOne

Ok I got the readings off my car.

* Voltage from the PCM no load..... 5 volts exactly

* Intake Bellows temperature (inside) 98* Farenheit

* IAT installed, voltage at the conector ...3.210 volts

* IAT resistance at 98* farenheight 1732 ohms


Using Ohms law I = V/R comes up as 1.8533 milliamps


** using SinisterSS values from Helm Manual the resistance
at 98* should be

1408 ohms

** using values from the Chiltons book the resistance
at 98* should be

1534 Ohms


** My IAT actual reading is

1732 Ohms


The difference from Helms is 324 ohms or 23% higher
Chiltons 198 ohms or 12.9% higher

either way it goes looks like my IAT is on its way out!!



I am buyin a new one and will compare results to the tables..

I hope this info gives a gives you guys a better idea....

Marvin