Well i tried searching on here and google and couldn't find it so could someone tell me what the voltage should be at the ecu pin. I still have bad mpg problems and want to check this I just can't find what the voltage should be at the pin on the ecu. I know it should vary but what is an acceptable range. At about 80 degrees out with the engine cold and not running but the key turned, i get 2.5v at the pin (d15) on the ecu. Does that sound right? If someone wants to check there's that would be awesome or if someone knows off the top of their head that would be great as well.

 

bump

 

come one guys i know somebody knows this at least if you don't know it off the top of your head can you get me going in the right direction to where i can find it

 

 

The way to know whether the IAT sensor itself is working properly is to measure resistance across the two IAT sensor terminals at various temperatures. Your resistance measurements should follow the relationship to temperature seen in the diagram in the post above. In addition to keeping your hair looking good, your blow dryer is also useful for heating and cooling the IAT sensor.

For your B16A2 engine, the IAT sensor receives 5V reference voltage on the GRN/BLK wire. Therefore, with the key in ON(II), you should measure 5V to ground from this wire terminal of the unplugged IAT connector.

The IAT sensor sends its voltage signal to the stock ECU on the RED/YEL wire that pins to ECU terminal C25. Make sure this wire has no open or short. The higher the air temperature detected by the IAT sensor, the lower the voltage received by the ECU.

 

Joel, it might be helpful to put details about your car (year, engine, ECU, mods, etc.) in your signature.

 

good idea will do, thanks for the info mtber and ron on how to test it as soon as i get home from fathers day shopping ill get right to it

 

okay so i am a little confused here is what i have when i unplug the plug from the sensor i have on the red/yellow wire 5.6v and the other wire is green/white that wire has no voltage on it and seems to be a ground although it is a little bit on the weak side. I know that the red/yellow wire has continuity to the ecu. Also i measured the resistance between the prongs and it was 1.2 kohms. Additionallyi found a site that had the voltage you should be getting at the ecu at given temps and mine lined up perfect although it wasn't for a civic i think it was for a ford ha. What do you guys think what confuses me is he fact that the wires seem messed up compared to what ronj said.

 

Sorry Joel. You have it right and I had it wrong. I gave you OBDII rather than OBDI wire colors. In addition, for OBDI, reference voltage comes from the Red/Yel wire and the Grn/Wht wire is indeed the ground. Seems like all checks out fine for the IAT sensor and its circuit.

TA sensor = IAT sensor

 

okay well i guess that is good i just wonder what else could be causing my mpg problem. Also to add to my observations of the idle it usually has a low idle when it hasn't gotten warmed up. When i first start it it's fine but then when i drive it a little then come to a stop before it's warmed up it will frequently drop very low rarely to the point of dying. Once it is warmed up it will idle around 700 but frequently it will jump all over the place. Also i have noticed it tend to be more jumpy when it is humid outside. Do you think my mpg and idle problems could be connected... I prly should start a different thread ha

 

also the other owner told me that the injectors were the stock ones from the engine but is there anyway to check that ie. if i remove them is there any good way to tell. Other than checking to hear clicking that is the only big thing i haven't checked yet

 

What is your city/hwy mileage? How many miles did you drive to come up with these figures?

In your signature, you might also state what specific OBDI ECU you have and the type of head on the B16A2 engine. Also, what sensors are not hooked up on the engine?

 

What comes to mind is a FITV problem where it is closing down air flow too quickly before the engine is actually warm. Later after the engine is hot, the FITV also inappropriately opens occasionally, leading to the idle fluctuation.

You could also have some air trapped in the cooling system. Have you done a thorough bleed? Have you checked the coolant temperature sensor?

Finally, any chance that you have an intake air/vacuum leak?

 

yes i did do a thorough bleed a while back, no i do need to check the ect, and i don't think there is a vacuum leak the engine shuts off within 1 or 2 seconds when i cover the tb

 

Hi Guys I measured as picture, is it my IAT sensor faulty ?

 

Have a look at this post and answer your own question. Is it in the allowable range for the sensor? Does it more or less correlate to the ambient temperature in the chart on the top right of the page?

 

If your getting bad MPG, check your O2 sensor, check your ignition timing with a timing light, check your IACV and clean it that will help with your low idle, If your IAT was bad the ECU would throw a code for it. Also old dirty spark plugs could give you bad mpg