They can get carboned up and stick in various stages of the operating range.

When changing the valve, be aware that the small screws that hold it to the throttle body have loctitie on them, if you try and undo them you will break off the screws. Heat them with a microtorch before trying to undo them, the heat breaks down the loctite.

 

 

 

All it does is add extra air when cold. The engine will be fuelled according to look up tables when starting and cold, so it won't save any fuel to leave the idle air controller disconnected. All you do is lose control over the warmup idle speed!

 

 

 

Depending on where the idle speed plunger stuck, there is always the possibility of stalling when in gear and the AC compressor engages.

 

Malfunctioning IACV causes havoc. Disconnected IACV results in overfuelling since the car must assume the amount of air coming into the engine.

After replacing the IACV, you'll likely need to have the TPS reset, which needs to be done with someone that has access to Jaguar specific software. The dealer will always have access to that, fewer independent shops will as well. That's been the case with my AJ16 engined cars. Everytime I swapped out the IACV, the idle ran high until the TPS was reset.

 

 

 

Vee, its not exactly true, TPS adaptation has nothing to do with IACV, nothing re IACV is stored in ECU and after replacing IACV you don't need to reset TPS. In a perfectly tuned up engine disconnecting IACV will cause slight drop in mpg and occasional stalling, especially when getting to a stop and are in eg 3rd gear, AC kicks in and RPM will drop and might cause a stall. It all depends on butterfly gap and how throttle body closes though so some engines where the gap is bigger than what it should be or doesn't fully close due to gunk or stretched linkage will run just fine with IACV disconnected and in fully closed position as the extra air needed to run engine will go through the butterfly gap.
All that is needed to get IACV in fully closed position on AJ16 engine is to cycle ignition few times, generally when you switch off the engine the iacv should extend itself, then go up a little, so next time you fire it up IACV is already in partially open position and allow a bit extra air on possibly cold startup. You can always connect a spare IACV, hold it in hands(to prevent plunger shooting out of the IACV) and have someone turn ignition key two position 2, wait few seconds and go back to 0 and wait again, this should explain best how it works and how to get it fully extended so when after replacing it you shouldn't have any high idle problems.

Hope that makes sense!

 

Katar83,

While on paper this may work, my experience has been otherwise. I spent a good amount of my life chasing down TPS and IACV problems. Eventually, after paying Jag specialists a few times for a reset, I found my own WDS and ended that! (Now I also have a PDU, I just don't have cables for any Jaguar vehicle without an OBD2 port!)

Anyways, I agree that changing the IACV should have nothing to do with resetting the TPS, yet for some reason, everytime I have replaced an IACV, a TPS reset seems to be in order. A manual reset of the IACV seemed to fix the idle, but only until the engine was shut off.

As for manually resetting the TPS, that indeed can be done too. I forgot about that. Slotting the two bolt holes so the TPS can be adjusted, while on the throttle body, with the car idling, you can slightly adjust the position of the TPS so that it idles correctly, then you can lock it in. There are indeed threads on that too.

 

 

I'm hoping you'll come back and wrap this one up for us.

 

 

 

 

 

Seems this part is no longer available. Does anyone know of a replacement from another model that will work or a rebuild/cleaning procedure?