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If anyone knows what these sensors are called and their function please advice. I think sensor C is the thermocouple for the radiator fans, but the other two I have no clue. The second photo shows another sensor I do not know what it's called or does and is located down there onto the throttle body/intake manifold (towards the driver side). It's on a 91 Accord LX manual transmission, F22A1 engine.
I'm having erratic idle all over the place sometimes stays high other times stays low and even pulses too at times, but whatever erratic idle the 91 Accord is doing it seems to stick to it for a bit but can change during a trip. I wonder if a faulty ECT sensor (A) or/and faulty intake air temperature sensor (?) might contribute to my erratic idle?
Faulty ECT or IAT will throw a code. They are both responsible for reporting their information to the ECU so that it can adjust fuel trims accordingly. If you don't have a code for either of those they're unlikely to be the culprits. That is assuming the cooling system is bled completely. If there's air in the cooling system it will cause all kinds of idle issues.
First thing I check on these old Hondas is the IACV(Idle Air Control Valve) when they come in for a bad/rough/surging idle. 80% of the time it's carbon build up in the IACV and throttle body causing the idle issues. A quick clean with some carb cleaner and they're usually good to go. If not I delve further from there.
The IACV is visible in your second photo. On the far left side of the photo, the black cylinder looking thing that has a single 2 wire plug and is attached to a larger aluminum piece. That whole unit is the IACV. It has 2 small coolant lines and a couple bolts attaching it to the intake manifold. Easy enough to pull, inspect and clean. Start with that and go from there.
When I started having the idle issue (started out as only low idle around 600 rpm) I did some research online and I decided to remove and clean the IACV (which had a good amount of carbon buildup on a mesh screen). But that didn't make much of a difference if any. I then proceeded to purchase a new IACV from O'Reilly which cost me "an arm and a leg". That didn't do much if anything either! Next in line was the FIV which I fiddled with and "cleaned" even though there was not much to clean (but I did not yet check to see if that brass plunger expands properly when the coolant gets bloody hot). Starting late last year, I decided to do some other maintenance such as clutch plate replacement (was at 200k miles with original still). I even replaced the oxygen sensor as preventive maintenance (I still don't know if that was a good call). Anyways, a few months ago I cleaned the throttle body in situ with lots of throttle body cleaner particularly aiming at the FIV and IACV ports just b4 the butterfly. After that, the idle was all over the place (low, high and pulsing). I now wonder if I dirtied the IACV by pushing dislodged material into it with the throttle body cleaner? Perhaps I should take it apart and clean it again. This makes me cringe because anytime I introduce air in the cooling system it takes lots of bleeds to get the air purged even though I follow the bleed procedure in Chilton's manual. An interesting thing I did just this weekend was that I "calibrated" the IACV per a thread in the Honda Accord Forums (https://www.hondaaccordforum.com/for...leaning-28486/) but all that did was make it significantly worse, so I reverted back to the way it was.
Right now the idle stays either too high or too low by a few hundred rpms. I still driving the Accord as a daily as long as I don't have all that pulsing idle, that's the one that really gets to me and it mainly happens when the headlights are on. But, now with the spring times no need to use headlight to and from work anymore here in AR, so rarely any pulsing idle.
Trying to ID these sensors >>>
