Hi everyone , recently got myself my first Jag, love it to pieces but unfortunately thats all i am doing with it at the moment taking it to pieces. It has a fast tick over currently running at 1400rpm. I have changed the air flow meter , the icsv, cleaned all the throttle body and checked for leaks but still she won't settle down. Anyone got any ideas? thanks in advance

 

I think??, haha, that the UK 3.2 is the same as ours in the colonies, NO EGR, thank goodness.

You have done heaps, and most of what I would have listed.

Remove the battery terminal, leave it sit for a while, go drink something, I use JD, and then reconnect. "SOMETIMES" that is all it needs to reset all the "Lectrickery" stuff.

Check that bellows that goes onto the throttle body lip, it can be a bugga to seat at the bottom, sometimes.

There was a recall waaaay back for the throttle return spring, under those arms dead centre on top of the throttle body, and that was due to throttle binding, and NOT returning to the stop as designed. There are threads in here about it.

 

Hi thanks for the reply. I have tried disconnecting the battery and no joy, everything is seated correctly just don't know what else to try. Even with the cable system off the top she still runs fast. Have spent the last 2 days on her but no joy. I am a gas fitter but no mechanic i am afraid but quite handy. I have even reset icsv valve but still nothing. First kick her up she revs for a split second settles down and sounds lovely for two seconds then just revs up to 1400 - 1500 rpm. Was wondering if it could be an automatic choke or something staying on, but like i say no mechanic, don't even know if she has one lol. Thanks again

 

And just for the heck of it, slacken and then readjust the throttle cable.

Over the years I've done battle with the high idle problem 2 or 3 times. The last time adjusting the cable did the trick. I simply did as I mentioned above.

I'm not sure why the cable would lose adjustment but I'm not arguing with success. In the back of my mind I've thought there might be a problem with the traction control unit (which the cables run thru) but that's another story and the car being discussed might not even be trac control equipped.

Cheers
DD

 

Never mind my suggestion!


Cheers
DD

 

Thanks DD. All advice welcome

 

Sounds like it needs the TPS orientation, as the computer thinks the throttle is open, so it won't control the idle motor to being the idle down ( it wouldn't, since it thinks it's not at idle).

If you have a OBDII scan tool you might be able to see what the throttle opening the computer is seeing. At idle it should be around 12%.

If you need to do the TPS reset it will need dealer level software, although an independant specialist should have it. Essentially it resets what throttle position the ECU knows as throttle closed, and then the idle air control circuit will work to control the idle.

 

Since you have had the problem before you cleaned the TB this probably is not the cause. But, when I cleaned my TB I forgot to connect the electrical cable to the bottom of the TB. This caused it to idle high also. Very dumb of me. After connecting it the idle was fine.

 

Sometimes solvent can cause TPS faults if it gets into the sensor.

PDU, WDS or IDS is required to perform TPS orientation/calibration but some people have cut slots in the mounting 'ears' to adjust it???

bob gauff

 

there was a recall, had mine change by jaguar dealership for free when i encountered same high idling, 1. EGR Valve.
2. ECU chips
3. throttle return spring
4. throttle bolt.
after the recall of parts and service everything went back to normal.

 

I still have some of the EPROMS I rescued from the trash bin back in 2005.

I don't think the Recall/Service Action is still active.

bob gauff

 

Hi Shawy,

I'm not an X300 expert so I've waited till others have given you input to see if your problem might be resolved. Since it appears you're still looking for ideas, I'll throw these out for consideration and discussion:

A vacuum leak or intake air leak is a common cause of increased idle speed. Depending on where the leak is located, it may also cause rough idle.

When you cleaned the throttle body, did you adjust the gap of the butterfly plate as specified (0.002" or whatever is recommended for an X300)? If the butterfly valve is not closing sufficiently your idle will be high.

Did the behavior change at all when you changed the MAFS and IACV? Were these new parts or salvaged? If salvaged, did you thoroughly clean the ISCV? It's possible that it's hanging up or not stepping properly. On our '93 I think I recall that both coils of the ISCV measured about 50 ohms. If the MAFS is providing an incorrect signal, or there is extra resistance in its electrical connector (if WD40 was used to clean it, for example), the ECM might be mistakenly raising the idle speed to compensate for a load that doesn't exist.

Here's some info from the AJ16 Engine Management System Dealer Training manual that may or may not be helpful:

"Idle speed is regulated by idle air control and ignition timing.

The idle air control valve (IACV) is driven by the ECM. The ECM uses inputs received from ignition ON, the crankshaft position sensor (CKPS), engine coolant temperature sensor (ECTS) and throttle position sensor (TPS), as well as inputs for ignition ON/OFF, gear position, air conditioning compressor operation and road speed to control idle." (pg. 6-6)

"ECM idle control occurs at closed throttle when road speed less than 3 mph. The programmed idle speed accounts for engine temperature and loads placed on the engine by the transmission (gear position N, D, R, etc.), and air conditioning compressor clutch operation.

"An ECM adaption function allows for a correction to the idle speed "base line" as the engine base idle changes with age. The adaption values are held in non-volatile memory (EEPROM) and will be retained even if the battery is disconnected." (pg. 6-8)

This may raise a few areas for exploration:

Coolant temperature sensor - if its resistance was too low (or its harness was shorted), the ECM might think the ambient air temperature was -22F/-30C and max out fuel enrichment. I don't know if this would be more likely to increase the idle speed or just cause a very rough idle, but you can measure the resistance of the CTS to see if it falls within the normal range. Some examples would be 5900 Ohms at 32F/0C, 3700 Ohms at 50F/10C, 2500 Ohms at 68F/20C.

In addition to the IACV with its stepper motor and variable opening, there is a non-adjustable fixed "Idle Air Bypass" that provides the base idle setting. I'm not sure where this bypass is, but if there was an air leak around that passage, then even if the IACV was fully closed the idle speed would be too high.

Gear selector - if the ECM thinks the gearbox is in Reverse or Drive when it is in Park, it may be mistakenly raising the idle speed to compensate for a load that doesn't exist.

AC Compressor clutch - if the ECM thinks the clutch is engaged when it isn't, that could also conceivably prompt a compensation that isn't required.

Those are my hair-brained ideas. Again, I'm no X300 expert, so I apologize in advance if any of these ideas are refuted by more knowledgeable members.

Cheers,

Don

 

TPS Orientation- Been there, done that!

 

Yep, TPS. Cleaning t body, extra wind on spring = waste of time on mine. New TPS and the car was perfect right away, with no issues for two years now.

 

I agree with a lot of the comments above. You almost certainly either have a vacuum/manifold leak or perhaps a problem with the TPS.

First thing I would do is hook up a scanner to the OBD port and look at the throttle position output. Normally at an idle of 700rpm you would see about 12% as the position output. If it reads much higher then check the throttle disc is closed and the throttle cable tension and return spring are set and working correctly.

There are lots of places that additional air can get into the manifold that you may not have checked. For instance the EVAP system or the brake servo hose if the purge/check valves are not operating correctly.

I would do all those simple and cheap tests before traveling to a dealer to have the TPS re-oriented, though ultimately that may be the ticket.

 

Hi guys, would like to thank everyone for their input into this fast idle problem and to let you all know after days of stripping the throtlle body and everything else i have finally cured her. The TPS was the fault but instead of taking her for plugging in i elongated the holes for the screws which Bob Gauff suggested and she now purrs like the cat she is. Thanks again guys, time to wash and polish her now(again) the joys of a black car and a neighbours tree.

 

The Technical service recall is still in effect, that is if your VIN number is included in the recall.