muddpigg

iTrader: (1)

IAT is that not the temperature apperatus that mounts to the upper intake plenum and increases idle when cold? Has coolant line that runs through it. Now that you mention it would make sense that the air inlet would be after being filtered in airbox. Guess mine was missing that air line. Truck was used so no telling what previous owner did good bit of wiring had been hacked.

jennygirl

That is the idle air control valve IACV, or aux air valve. In 85-88, it is an external unit mounted beneath the plenum and in 89+ it is integrated into the throttle body. It has an air valve that opens/closes based on the temp of the water going through it. There are two water lines hooked up (in/out) and in the 85-88 there is an air bypass hose that goes past the throttle plate. In the 89+, it is all incorporated into the throttle body.

IAT is a thermistor that lives in the front of the AFM. If you remove the AFM from the air filter you can see it- in the earlier models it is a small black cone shaped thing about the size of a pencil head. In later models it's a bit smaller and has a clear plastic thing over the tip of the cone. This sensor gets to the ECU by means of the AFM connector, and helps the engine determine how to balance air/fuel mix.

The IACV only controls idle up for cold condition, it doesn't have anything to do with air/fuel mix

muddpigg

iTrader: (1)

Can't say I'm noticed it but curious and will take a look. Thanks

jennygirl

picture is worth a thousand words



that is a supra AFM, but it looks the same on the 22re AFM

jennygirl

So basically what happens it the heat from the engine spreads to the AFM once turned off (no longer air blowing in to keep it cool and no air consistently rolling past the sensor). Heat soak. Low lean idle until airflow eventually cools down the AFM and sensor.

During throttle open with AFM still heat soaked, there is enough airflow to give the sensor a proper reading and the engine revs fine. Returning back to idle allows the heat from the AFM to spread back to the sensor.

This is why I think the low idle issue disappears once you get moving down the road a bit. The AFM needs some time to get un-heatsoaked. Pouring icewater on it speeds it up.

Mounting the temp sensor farther away should solve this. I'm going to test it!

muddpigg

iTrader: (1)

Just haven't seen others have this problem. BBP has been running it for quite awhile and never mentioned it.

An intermitten short could short could fool it too.

Let me know what you figure out.

jennygirl

Starting to doubt myself now. I got the car up to operating temp and swapped AFMs (I have two) meaning the one I put on was most definitely not heat soaked. No change- the car still idled like crap until I revved it and let it sit for a while

Just installed my flamethrowers and about to test drive!

Smeddy2

Anxious to see how it goes! I'm having the same problem and am about to either order some flamethrower or send my old ones off to witchunter. Mine has fuel pressure bleeding off, hard cold starts and hot starts (used to just be hot starts), rough and/or low idle and bad gas mileage.

muddpigg

iTrader: (1)

I agree pics are worth a thousand words

jennygirl

I'm not sure what to think of the IAT anymore, I still wanna try the relocation mod.

My prime suspect right now is the fuel pressure regulator. If you can't tell, my prime suspect is on continual rotation with this issue.

The idea with the FPR is that the pressure up diaphragm eventually goes bad which leaks the fuel pressure back through the vac line into the intake. Seems there are many other cars that can have this problem.

I have a new denso fuel pump, new remanned flamethrowers, and the CSI doesn't leak. So, that leaves the FPR (for the disappearing fuel pressure).