Idle air control valve

I’m having some idle issues on my 97 xj6. I never had idle issues before on this car. The other day I started it and the idle went up around 1500 and stayed there, even when the car is fully warmed up. Members on other Jag forums say it may be the Idle air control valve. If I replace it does anything need to be calibrated / recalibrated? Also cost, AutoZone wants $185.00 for one other auto parts places it’s between $15.00 - $30.00

The first thing I would do is to make sure the throttle plate is closing properly.

03-1-15 Throttle Difficult to Open on Cold Engine.pdf (67.7 KB)
05-1-15 Intermittent High Idle.pdf (127.2 KB)
05-1-26am5 1995 MYRecall R493.pdf (256.2 KB)

If all the mechanical aspects seem OK than I would try a TPS calibration.
I have 3 WDS and 2 IDS so I am at an advantage being able to do this myself without the dealer or a shop with this equipment.

The IACV small fasteners use a threadlocking compound so you might break them off in the throttle housing when you try to remove them.

I used to go around the dealer shop when I worked there and collect the throttles that had the broken fasteners stuck in the threaded holes.

I had good luck (and patience) getting them removed with a butane pencil torch and small pliers. Sometimes a left hand drill was required.

Many GM cars/trucks use the IACV so they are cheap.

When taking all the plastic and rubber housing off from the air filter to the throttle body I noticed inside one of the pieces was covered with black greese grid, also inside of the throttle body before/ after the butterfly. I read on other forums this is from the EGR valve.I was going to take the throttle body off to give it a good cleaning but couldn’t get the connector off the tps and didn’t want to break it. Just cleaned everything I could reach. I will see if this helps with the idle.

No the IACV (stepper motor) does not need to be calibrated. Buy the aftermarket one from SNG Barratt if you need one.
The TPS connector is the same as the MAF sensor connector. If you depress the metal retaining clip FULLY it should come right off. Might be a little stuck. Spray with electronics cleaner if necessary. Should pop off. IIRC you can remove the throttle body with the TPS connected and rotate it so you can get to the connector easily.

  1. Clean the MAF meter with MAF cleaner spray.
  2. Clean the MAF & Air Temp Sensor Connectors with electronic cleaner.
  3. Thoroughly clean out the plastic plumbing.
  4. Closely examine the bellows that connects to the TB for holes.Thoroughly clean it.
  5. Remove the TB connector and TB itself.
  6. Clean the TB & TPS & IACV THOROUGHLY. Toothbrush needed. If you are not changing the IACV spray it thoroughly from inside the TB. Use Throttle body cleaner.
  7. Spray the accelerator spring mechanism thoroughly.
  8. Remove and thoroughly clean the EGR valve.

Make sure you re-connect the secondary air pump hose to the filter housing.

See where you go from there. The IACV is cheap so it wouldn’t be a big deal to replace it. It’s easier to get off when the TB is on the bench.

From Vauxhall/OPEL TBIs I learned that the seat of the IACV gets hammered so badly over the years that it can’t seal anymore. The plunger/piston of the IACV is not guided properly to hit center.

Also, back then we dealt with two different IACVs, having different piston tips. Check that when you buy a replacement - in case Jaguar also has variations. One was more tapered, the other more pointy. AC Delco, if I remember correctly.

You could then reset it by revving the engine to approx 3.000 rpm after disconnecting the IACV or its 4-pin plug. During reset your idle will briefly drop below the set value. They operated on AC.

I cleaned the throttle body, butterfly with it still on the car and that rubber piece with all the oil grud in it. Re assembled everything and started the car. The idle is back to normal. When it cools off here in Phx I will take the throttle body off and do a thorough job cleaning it. Thanks everyone for your help. I have two other Jag ( xjs ) with the V12, this 4.0 is new to me