so my 04 x has normal idle in park, nuetral or in gear until i let off the brake, as soon as the wheels roll even a fraction, it revs up to15-1700 rpm and drives away! it will actually shift into 3rd without touching the throttle! if i push the petal it drives normally and shifts normally except when coasting, the rpms slow down with the vehicle till around 1200 then jump up to 1700 and back to 1200 a couple times before staying in the 1700 range. as i come to a stop, im pushing unnecessarily hard on the brake as i'm fighting the motor. once at a complete stop the idle rests back just below 1k. no codes no lights clean tb. any help is appreciated.

 

Couple of things, a small vacuum leak will cause high revs. Throttle position sensor can also cause it. Lastly is idle speed control valve and/or carbon build up in the inlet port where it installs.

 

tps was one of my thoughts as well. will the IAC valve need a new gasket if removed for cleaning? i have video of the gauges in action while driving but not sure how, or if I'm even allowed to post it since I'm new to the forum.
the car also feels like a manual trans car when you let off the gas at highway speeds too...you know that weight transfer when on or off throttle that torque converters usually eliminate? it has me worried that the converter could be locking all the time causing these issues. just a thought.

 

Well for a couple of dollars, I would.

 

Hey there! My car won't idle and I'd like to clean the IAC. Where is it?



Thanks!

 

I just found this quote from Thermo in 2012 when I asked him about this, Lol.

"Patterson ,the IAC is built into the throttle body. If you look on the throttle body, you will see a small hole on each side of the butterfly valve (large metal plate that blocks the air flow). Take some throttle body cleaner (not carb cleaner) and spray it down that hole. Might as well clean the whole throttle body at this point too. That should clear that up."


However, I'm not finding those holes.

 

First post has description and pics

https://www.jaguarforums.com/forum/x...roblem-113287/

 

Dell / Patterson: You may be conflating two IAC valves: INTAKE air control and IDLE air control.

INTAKE air control valves, aka Intake Manifold Tuning and IMT valves. Our X-Types have 2 in the intake manifold farthest from the throttle body, known for leaky O-rings. They adjust the intake airflow so that at high RPM / high airflow sufficient air is diverted to the #5 & #6 cylinders (closest to the throttle body) and at low RPM / low air flow, sufficient air makes it to #1 & #2 cylinders (furthest from throttle body).

IDLE air control valve, aka Idle Speed Control valve: If I'm reading the X-Type shop manual correctly, 2.0L engines have a separate idle air control valve, but 2.5L and 3.0L engines do not. The idle air control value fine tunes the volume of air bypassing the closed throttle plate at idle. See attached pictures. In Lexus' and Toyota's, I've degunked clogged idle air control valves - the classic symptom is rough cold start. But I haven't yet found this part on my 2.5L X-Type, nor in the X-Type shop manual except on 2.0L's. Could be wrong - not the first time, and won't be the last.

 

dwclapp, Thanks for continuing to entertain the Jag hi-jinks going on here and there! Let's say that the Idle Air Ctrl valve is worked into the IMTs on our mostly Duratec engines, but I don't understand how that can work bc the IMTs are furthest from the throttle body's circular plate valve. The X Type throttle body just doesn't have an IAC valve. What you said about the IAC function is:

"The idle air control value fine tunes the volume of air bypassing the closed throttle plate at idle."

If the X has an IAC, it would have to be near the throttle body plate, (butterfly air valve) but there is nothing there. Also, I know it's more syntax than anything, but air cannot bypass a closed throttle plate, can it? I think the plate has a default opening of a few degrees for idle.

Many cars have an easy to see IAC and people pull it off and clean it with brake cleaner or the like, but I don't find anything like that on the X throttle body or the upper intake manifold.

I haven't pulled my IMT valves since about 7 years ago when I replaced the poopy stock O-rings for the thicker gauge replacements, so the question becomes, Can one pull the IMTs and have some luck spraying them clean with a solvent?

 

 

Dell: Thanks for the Idle Air Control valve pic. I didn't know our X-Type's had these. If my 2002 X-Type 2.5L Sport has one of these, I haven't found it yet, and I've had the throttle body, air box and intake off a few times. Where is it located on your X-Type?

Patterson: Idle Air Control valves need to be cleaned / degunked on high mileage cars. When gummed up, the idle is rough, particularly on cold starts. Intake Air Control valves, aka IMT valves don't need to be cleaned from my experience. The only maintenance is new O-rings when they leak air into the manifold.

 

In workshop manual on page 53, 352 & 362

 

Btw, IMT stands for Induction Manifold Tuning

 

Here's a mechanic's explanation of Idle Control Valves =

The idle control valve, also commonly referred to as the idle air control valve, is an engine management component that is found in one form or another on the majority of road going vehicles. Its purpose is to control and regulate the engine idle speed, increasing and decreasing it as necessary to keep up with operating conditions.

Most idle control valves come in the form of a motorized valve or motor that is mounted somewhere on the vehicle’s intake manifold. The valve or motor is controlled by the engine control module, which will adjust the idle speed according to parameters such as engine temperature and electrical system load.

When the idle control valve fails it can cause all sorts of issues with the vehicle, and in some cases may even render it undrivable. Usually a bad or failing idle control valve will produce a few symptoms that can alert the driver of a potential issue.

1. Irregular idle speed

One of the most common symptoms commonly associated with a problematic idle air control valve is irregular idle speed. The idle air control valve is programmed to regulate and maintain the engine idle speed at a constant rate. If the valve fails or has any issues it can cause the idle speed to be thrown off. This may result in an unusually high or low idle speed, or in some cases a surging idle speed that repeatedly climbs and falls.

2. Check Engine Light comes on

Another symptom of a potential issue with the idle control valve is an illuminated Check Engine Light. If the engine control module detects an issue with the idle air control valve circuit or signal, it will set off the Check Engine Light to notify the driver that there's an issue. The Check Engine Light can also be set off by a wide variety of issues, so having the computer scanned for trouble codes is highly recommended.

3. Engine stalling

Another more serious symptom of an issue with the idle control valve is engine stalling. If the idle control valve fails completely, it may leave the vehicle without a source of air to maintain a proper idle. This may result in the engine stalling while operating, and in some cases may result in an engine that will not idle at all, and stalls as soon as it is started.

Usually a faulty idle control valve will produce symptoms noticeable enough that the driver will quickly become aware that there is an issue.

 

Dell: Thanks for the insight. Mystery explained........

Jaguar's EPC shows 2 very different throttle bodies in our X-Type's:

1) For 2.0L Petrol engines, a cable controlled throttle with an idle air control valve sitting atop, #1 in the attached parts diagram. Jaguar prefers 'bypass valve'

2) For all other "except 2.0L Petrol engines", a "fly-by-wire", servo-controlled throttle, without idle air control valve, #6 in the parts diagram.

For a moment, I was ready to run outside with a flashlight and look for the missing idle air control valve on my 2.5L X-Type. Glad I stayed inside.

Everyday we learn something new is a good day!

 

Wouldn't that be the TPS (throttle position sensor) on the fly-by-wire later model throttle bodies on the Duratec engines?

 

Dell: My apologies for not explaining Jaguar's EPC more clearly. Perhaps SNG Barratt's parts diagram lends clarity - it's consistent with the EPC: https://www.sngbarratt.com/us/#!/Eng...HROTTLE%20BODY

Item #1 - dashed rectangle encompasses the entire "Throttle housing, 2.0 Litre petrol", including item #2 - "Bypass valve", aka idle air control valve.

Item #6 points to the TPS (throttle position sensor) and is described as the entire "Throttle body, Except 2.0 Litre petrol" (includes TPS).

Hence mystery explained: Our X-Types apparently have an idle air control valve on 2.0L petrol engines with cable-controlled throttle bodies, but not on 2.5L & 3.0L engines with servo-controlled throttle bodies.

Thanks for adding to the knowledge of our X-Types. Personally I'm relieved my 2.5L does not have an idle air control valve: they require periodic cleaning, and I'd kick myself for not recognizing an obvious part if my X-Type really had one.

If your 3.0L has an idle air control valve, please share a picture to educate us.

 

Hello jaguar x type vehicle data engine 2.0 d engine idle speed 900 rpm, 2.2 d engine 800 rpm it says. However, 3.0 L engine's idle speed value does not write. Where is the idle speed of the 3.0 L engine?