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Intake Air Temperature (IAT) Sensor

-Rich-

-Rich-

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Location
Herts
Car
2.4 Tourer Auto
I am still having issues with my revs bouncing occasionally while I'm driving at low speed. I have now found out my car doesn't have a MAF just the IAT sensor on the intake hose just before the throttle body.

#14 on this diagram - http://www.lingshondaparts.com/honda_car_parts_selection_pfk.php?block_01=17SED01&block_02=B__0100&block_03=443

I have tried to remove it once before to clean when I did the throttle body but it was being stubborn and I didn't want to force it. Should these just pull out, do they break easily?

Is there a way to test this sensor, how can I find out if it's this causing the issue? I can't find any used (or new) ones for sale on ebay, although I've not searched the cars getting broken yet. A new one is around £50 so I'd rather try a used one first in case this isn't the problem.
 
Clean your throttle body butterfly valve out mate.. Restriction in the valve movement will cause this feathering problem
 
Undo the circlip holding it and pull it straight out - they are sitting in the rubber are not very fragile, but don't take rough treatment either. Make sure it's not stuck with gunk. Only test I've ever found is to try a swap.

You also have a MAP sensor as well.
 
I have already cleaned the butterfly but will do it again. I just pushed it open to clean but have since read with drive by wire you shouldn't do this?

I removed the MAP sensor and it looked clean. I'll have a go at taking the IAT sensor out.

The problem seems to be getting worse so I need to sort it out.
 
Unless you've some components to swap, you'll need to get this onto a diagnostic to test the range of the sensors :( Or take a gamble on the MAP/IAT sensor.
 
jayok said:
Unless you've some components to swap, you'll need to get this onto a diagnostic to test the range of the sensors :( Or take a gamble on the MAP/IAT sensor.
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I'll try and get hold of a sensor to swap it over.

It's a right PITA cos it's spoiling the enjoyment of driving the car :(
 
Right, one last go at trying to sort this before I have to take it in somewhere.

I changed the spark plugs with some Denso ones and the car seemed to run smoother after this. One of the old ones was actually lose as well, it hadn't been torqued or had worked lose.

I did the oil change at the same time cos that was due, although this obviously won't be the cause of the problem.

I managed to get the IAT sensor out and was surprised to see it's incased in plastic, I was expecting to see an exposed wire. I sprayed it with some cleaner, air dried it and refitted. After doing this things seem to have got slightly worse but I'm not sure if it's a coincidence or not. Only found one sensor for sale so far and they want £23 for it, which is half a new one from Honda.

These are the symptoms I'm getting now:

When I accelerate and then lift off the rev counter drops to as low as 650rpm, even when I'm doing 50mph and then goes back up again. Sometimes it can be ok for a while when I lift off but as soon as I brake and start slowing down it does the same thing. The car seems to be driving fine though and changes gear accordingly when I change over to semi auto to check the gear number in the display, the revs certainly don't match the engine speed.

Does this sound like it's the IAT sensor or could something else be causing it? When the car is idling in P, N or D I don't have this problem at all, would a faulty IAT sensor cause idle issues. The revs stay at 650rpm and may increase slightly if I use any of the elctrics, it's only doing it when I'm driving.

To top it all off I noticed one of the rear brakes is hot and smells abit so looks like that is starting to bind! :(
 
When you say you let off, do you mean if you let off the accelerator it drops to 650rpm? (you've an auto so you're not clutching).

And it doesn't do it in N or P? If you floor it in N or P and let off does it drop back to 650 then? If it's ok here, the in the IAT and MAP are probably ok. You mentioned brakes are binding, is the initial load from the car dropping onto the load of the engine?
 
jayok said:
When you say you let off, do you mean if you let off the accelerator it drops to 650rpm? (you've an auto so you're not clutching).

And it doesn't do it in N or P? If you floor it in N or P and let off does it drop back to 650 then? If it's ok here, the in the IAT and MAP are probably ok. You mentioned brakes are binding, is the initial load from the car dropping onto the load of the engine?
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Yes that's it, I could be doing 50mph, take my foot off and it drops to 650rpm before rising again. It starts from around 20mph, under that speed the rpms are quite low so it's either not doing it or I don't notice.

When I mentioned N and P I mean with the idle, that's perfect and stays where it's suppose to. Increases when you turn the wheel, switch the front/rear screens on etc so that's all fine.

I think the IAT and MAP sensors are fine like you say, this does seem to be throttle related (I have another thread about that!)

One rear brake has only started to bind, on a long drive it was slightly warmer than the other side with a hint of burning smell. I'm going to strip them down the weekend and grease the slider pins, check the pistons and pads.

I'm not sure what you mean about the load of the car/engine?
 
When it P / N at idle, if you rev the car and take your foot off the accelerator does it also drop to 650rpm?

As the engine adjusts to the additional load of the PSP and/or A/C, then I reckon the IAT and MAP are fine, you're right, I'd focus on the TPS.

For the rear of the calipers, make sure you clean the brackets of rust, etc. I too had this on my tourer.
 
Yes it does but then it should do that anyway as the car isn't in gear?

I know all about cleaning calipers, had to replace 3 on my last car cos they kept seizing up, whether it be the pistons or sliders - nightmare!
 
Yes, it should my question was "does it drop back to the idle speed correctly or below it". If it's dropping back to idle speed correctly, then I' going with the TPS on this.

Did you try a reset of the car? e.g. battery out for 10mins? Reset the TPS?
 
jayok said:
Yes, it should my question was "does it drop back to the idle speed correctly or below it". If it's dropping back to idle speed correctly, then I' going with the TPS on this.

Did you try a reset of the car? e.g. battery out for 10mins? Reset the TPS?
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You said does it drop to 650rpm, which it does, not below it - unless I've missed that bit.

I pulled the ECU fuse to reset it, that works as well doesn't it? Can you reset the TPS? I did the idle learn procedure after resetting the ECU.

I'll disconnect the battery tomorrow and do it again see what happens.
 
Yep you can reset the TPS, but you need Honda's HDS for it :(

Just as a side thought, does the gearbox feel ok? Could it be that the gear changes are sluggish and it's confusing the DBW?

When did you last change the ATF? Does reverse select cleanly and quickly? What mileage are you on?
 
jayok said:
Yep you can reset the TPS, but you need Honda's HDS for it :(

Just as a side thought, does the gearbox feel ok? Could it be that the gear changes are sluggish and it's confusing the DBW?

When did you last change the ATF? Does reverse select cleanly and quickly? What mileage are you on?
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I met up with Fahad last night, luckily for me he is staying in the area :)

When I left home the CEL came on, first time this has happened. He plugged the HDS in and the code was for low voltage on the TPS or wiring. There were also a couple of others stored on there that my OBDII reader couldn't see but these were auto wiper and battery related so cleared those as well.

The TB was opening/closing ok using the test on the HDS and the voltage for the TPS seemed to be ok, ranged from 0.45 to 4.5v. The CEL hasn't come back on but I've still got the problem. I'm on the look out for a cheap TPS to swap them over and hopefully that will sort it.

Also it looks like it can't be calibrated on my car, the option in the menu to do it wasn't there.

With the gearbox it was changed 25k miles ago but it's been over 4 years so it does need changing, which I'll do asap. The gear changes aren't as smooth as what they were a couple of months ago (only had the car 3 1/2 months), but I don't know if that is oil related or this issue causing it. Reverse seems fine, no issues with selecting it and I've a 100 miles to go until I hit 100K.
 
Hi Rich,

The specific error was Accelerator Pedal Position sensor voltage low A and B.

As B is half the voltage of A its possible one triggers the other.

The APP is the same sealed unit where the potentiometer sits in the cable housing so you would need to change the whole unit.

Try and get one cheaply so you are not out of pocket for much if it transpires to be something else.

The throttle position sensor actually sits inside the throttle housing next to the actuator and measures the throttle position.

If there is an issue with that you normally get a correlation error which I've seen previously I.e the correlation between APP and TPS is mismatched.

The error you were getting is specific to the APP so that's what I would investigate further. Could be the wiring or the part itself.

Hope that helps
 
Thanks Fahad.

I was getting mixed up between the APP and TPS. Been reading too much on the subject no doubt and what everyone calls them has confused me! :wacko:
 
I have found something out, which I didn't think to do before.

When I had previously locked the car into 2nd gear to test the rpms dropping I was only changing at 2-2.5k rpm. On the way home last night and this morning I mainly stuck to 2nd and revved it to 4-5k rpm and it was fine! Can't do it in 3rd or 4th until I'm on a faster road but when I accelerated to 2k rpm or slightly over and let go the revs drop and then rise again. Anything above this and the rpms drop slowly and smoothly! :blink:

I'm not sure what this means now? The car drives fine, it accelerates fine, changes gear ok and when the rpms on the dash drop the car doesn't act like the brakes have been slammed on, i.e. the fuel has been cut off and it doesn't change down a gear. It just dips and then increases so maybe this sensor just has a bad spot (or whatever the term is) that means when I lift off at 2k rpm they drop but after that and it doesn't. I'll also add that I sprayed the connection on the sensor and plug with contact cleaner, which I think made things slightly better or it could just be the placebo effect. Could a dodgy ground be causing this?
 
Definitely sounds like an electrical problem with the APP. Remember the specific error suggested the voltage was low.
 
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