1988 where is the intake air temp sensor

[cruiser88]

A Service warning is appearing on my dash, i have a 3.8 v6 EFI multiport engine. My EEC4 scanner gives me code 24 - IAT intake air temp sensor out of range. I bought a new one. But I can't find such a sensor anywhere on the engine. The Ford shop manual does not show any sensor, although the wiring diagram shows wires and a connector. My Haynes manual for 87 & 88 shows an IAT sensor in the air filter housing of the 87 but not the 88. I've thoroughly checked the engine and don't see anyplace to install that new sensor I bought. My mechanic friends say the ECM does need a temperature signal. Can anybody tell me where the IAT sensor is on the 3.8 v6 multiport EFI engine?

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[mcm51]

On my '95 4.6, the IAT is located on the air filter box because it has to be read before the mass-air sensor, in your case, without mass-air, the IAT can be anywere from your air-silencer box all up the air-intake tube to the motor, check the entire distance, air-silencer box will probably have to be checked from underneath...........
You are sure an '88 3.8 uses a IAT, I thought that was something that came along in the early '90's ??

 

[mcm51]

Yep, check the entire air intake tube from the air-silencer box, if you have one, that might be located under the air filter box, all the way to the throttle body AND it's probably possible to even have that IAT mounted just past the throttle body or just near it..........
Think about it this way, it's got to read that air temp before intake air reaches combustion chamber, you'll find it.............

 

[cruiser88]

On my '95 4.6, the IAT is located on the air filter box because it has to be read before the mass-air sensor, in your case, without mass-air, the IAT can be anywere from your air-silencer box all up the air-intake tube to the motor, check the entire distance, air-silencer box will probably have to be checked from underneath...........
You are sure an '88 3.8 uses a IAT, I thought that was something that came along in the early '90's ??

Thanks for the reply! Actually I've dismantled the air box, checked under the intake manifold runners, the front and rear of the motor, and traced every bit of wiring in the engine compartment. Nada. Like my certified Ford mechanic says, the Ford wiring diagram indicates an IAT exists, but none of the physical diagrams show an actual sensor. Another mechanic who pays for a service that provides diagrams says the same thing; no photo of the sensor. It must exist, it is a listed Ford part, Rockauto shows a listing, and I bought one from Partsource. I thought if I bought one I could use the shape of the connector to locate the wire leading to where its installed. There are several unused connectors around the motor but none of them match the plug on the sensor I bought.
One thing everybody agrees on is the ECM needs a temperature reading. The "service" light is on my dash and my scanner says the IAT is "out of range"...

 

[mcm51]

I know rockauto lists a IAT but I have found them wrong before on my Bird, I used to work on a friend's '85 3.8 back in the 90's all the time and I really don't recall it having a IAT, that's why I really don't recall Ford using IAT's till OBD II came along......That does'nt explain your code saying you need an IAT, I'm kinda suspect of the code itself, 24 sounds like a strange number, mines like 3 and 4 digit but without OBD II, you must be reading this code from counting lights from under the hood or off the inst. cluster, I'd almost ask ya to go back and make your getting that code count correct........
In any case, If the motor wants to get a correct incoming air temp reading, it's got to be read before the throttle-body or near it, any further down the line the air would start getting affected by heat off the engine........
You never mentioned an air-silencer box, if you have one , maybe not, it's been a long time since I worked on 3.8's......It could get an incoming air temp reading off the silencer box......

 

[cruiser88]

On my '95 4.6, the IAT is located on the air filter box because it has to be read before the mass-air sensor, in your case, without mass-air, the IAT can be anywere from your air-silencer box all up the air-intake tube to the motor, check the entire distance, air-silencer box will probably have to be checked from underneath...........
You are sure an '88 3.8 uses a IAT, I thought that was something that came along in the early '90's ??

Thanks for the reply! Actually I've dismantled the air box, checked under the intake manifold runners, the front and rear of the motor, and traced every bit of wiring in the engine compartment. Nada. Like my certified Ford mechanic says, the Ford wiring diagram indicates an IAT exists, but none of the physical diagrams show an actual sensor. Another mechanic who pays for a service that provides diagrams says the same thing; no photo of the sensor. It must exist, it is a listed Ford part, Rockauto shows a listing, and I bought one from Partsource. I thought if I bought one I could use the shape of the connector to locate the wire leading to where its installed. There are several unused connectors around the motor but none of them match the plug on the sensor I bought.
One thing everybody agrees on is the ECM needs a temperature reading. The "service" light is on my dash and my scanner says the IAT is "out of range"...

I know rockauto lists a IAT but I have found them wrong before on my Bird, I used to work on a friend's '85 3.8 back in the 90's all the time and I really don't recall it having a IAT, that's why I really don't recall Ford using IAT's till OBD II came along......That does'nt explain your code saying you need an IAT, I'm kinda suspect of the code itself, 24 sounds like a strange number, mines like 3 and 4 digit but without OBD II, you must be reading this code from counting lights from under the hood or off the inst. cluster, I'd almost ask ya to go back and make your getting that code count correct........
In any case, If the motor wants to get a correct incoming air temp reading, it's got to be read before the throttle-body or near it, any further down the line the air would start getting affected by heat off the engine........
You never mentioned an air-silencer box, if you have one , maybe not, it's been a long time since I worked on 3.8's......It could get an incoming air temp reading off the silencer box......

I used a proper Equus code reader. I think it works because I fixed another issue, erased the codes and "Service" light on the dash went away. Then only the IAT code came back. I kinda know what I'm looking for, my 95 F150 5.0 (also with EEC IV), has the sensor on the air box. My 1990 F150 5.8 is supposed to have the sensor on intake runner #5, sensors are calibrated for their location. I once had a TBI Escort, the owners manual actually said if the temperature changes a lot from the last time you drove it, you must run the motor a short time, then turn it off and "key on engine off" to let the IAT reset the ECM, then the motor runs better. In the Fall my escort misfired on cold mornings until I discovered this protocol. I say this because my Tbird 3.8 is low km, EFI, tuned up, but it burns 12 lires/100 km, driving slowly on flat highway asphalt. Not good. I can live with a Service light on, but I suspect a bad sensor could be responsible for my bad gas mileage. And then there's the fact that Ford shop manual indicates an IAT...
I think my problem is an 88 Tbird 3.8 Multi port EFI - only issue. Where is that sensor????!!!

 

[mcm51]

I'm about out of thoughts on that IAT, I had that thought too about "if I have to drive with engine light on", yea if I did'nt have any issues,
I'd take the bulb out on that light panel if I had too.......I had too take my bulb out on my '95 because I've got a plugged egr tube and it keep spitting that code out, keeping annoying light on, someday I'll get to that egr tube and put my bulb back in........I mention that because I know what it's like to drive around with that light on............
OK so you've checked more than once on that DTC and it's correct.....just for my thought, and make sure I'm correct(I'm been working on 4.6's for quite a while) your '88 3.8 is a T.B.I. vs. mutiport injection ? so you have the old time round air cleaner with the old time round lid on top ? vs. the new stuff(I call it) were the air cleaner is way over by the fender(my 4.6 and I guess your '95 5.0)..........in short, both 95's should have an air silencer box under air filter box, so if your 3.8 is T.B.I with round filter box, your air intake tube(dual or not?), if you still have the intake tubes would run over to openings in the fender, now here's what I'm getting at, IF this car is using an air silencer box about the only place you could put it on your set-up is in the fender above the tire fender liner, you'd have to take your tire fender liner out to get at it AND that's where your's may be placed if you have one...........That's about all I can think of on that *amn I.A.T..................

Gonna throw in a thought here, on that fuel mileage, if the car is low mileage maybe it does'nt need o2 sensors, but could maybe use a throttle body injector flush, Ford use to call it, now air/fuel injection flush, you also might want to consider BG fuel system cleaner, what my dealer uses...........you probably know all this, ya sound like a Ford man with T-bird, F-150 and Escort mentioned................

Like I said, if your still searching for that I.A.T. consider checking right on the other side of that fender wall where the intake tube goes.......

 

[cruiser88]

I'm about out of thoughts on that IAT, I had that thought too about "if I have to drive with engine light on", yea if I did'nt have any issues,
I'd take the bulb out on that light panel if I had too.......I had too take my bulb out on my '95 because I've got a plugged egr tube and it keep spitting that code out, keeping annoying light on, someday I'll get to that egr tube and put my bulb back in........I mention that because I know what it's like to drive around with that light on............
OK so you've checked more than once on that DTC and it's correct.....just for my thought, and make sure I'm correct(I'm been working on 4.6's for quite a while) your '88 3.8 is a T.B.I. vs. mutiport injection ? so you have the old time round air cleaner with the old time round lid on top ? vs. the new stuff(I call it) were the air cleaner is way over by the fender(my 4.6 and I guess your '95 5.0)..........in short, both 95's should have an air silencer box under air filter box, so if your 3.8 is T.B.I with round filter box, your air intake tube(dual or not?), if you still have the intake tubes would run over to openings in the fender, now here's what I'm getting at, IF this car is using an air silencer box about the only place you could put it on your set-up is in the fender above the tire fender liner, you'd have to take your tire fender liner out to get at it AND that's where your's may be placed if you have one...........That's about all I can think of on that *amn I.A.T..................

Gonna throw in a thought here, on that fuel mileage, if the car is low mileage maybe it does'nt need o2 sensors, but could maybe use a throttle body injector flush, Ford use to call it, now air/fuel injection flush, you also might want to consider BG fuel system cleaner, what my dealer uses...........you probably know all this, ya sound like a Ford man with T-bird, F-150 and Escort mentioned................

Like I said, if your still searching for that I.A.T. consider checking right on the other side of that fender wall where the intake tube goes.......

Actually my car is multiport EFI not TBI. Even my skimpy Haynes manual shows info on the temp sensor in the old style air filter housing of the TBI engines.

I have checked all around the air box..trust me,while restoring the car I replaced both front fenders, I've had a look at everywhere wires run!
I don't mind the "Service" light being on this electronic dash, it's dim, not like the check engine light.

I've done a tune up and put injection cleaner in the tank. I do believe the fuel economy problem is related to the missing IAT signal, the ECM is generating an error code so it must have something to do with engine management.

I'm at the point of opening up the wiring loom. I know the pin on the ECM module and the color of the wires that should connect to an IAT sensor. Maybe I'll have to add something that Ford forgot to install.
I was hoping somebody out there with a 3.8 EFI multiport could tell me where their sensor is!

 

[cruiser88]

Hey guys that I'd report the good news the IAT was on the lower intake manifold. Hid really well!! I could just barely get a socket on it but i swapped in a new one. Way better gas mileage and no more misfiring!! Also the Service light was a reminder to change oil, it is reset by holding in 2 buttons on the dashboard.