Hello everybody,
I've got my 96 jag that runs great except when it stalls out on me sparodically at red lights or stop signs. i can't reproduce it as it just starts to happen. I notice that with the air on it's less likely to stall on me. I usually just shift Jag into neutral at stops to keep engine reving a little bit above normal idle.. From reading the various posts etc, i think it's the idle air control valve ? Where is this connection made should I wish to unplug it to see if it makes a difference? any advice would be greatly appreciated.

thank you,

greygoose.

 

The idle control valve is a small cylindrical device, sitting upright on top of the throttle body, slightly to the rear of it, that is, nearest the windscreen. You will see a black push on electrical plug sitting on the top of it.

Also worth looking at is the possibility of any slack on the throttle cable. There is a tiny grub screw which adjusts the throttle cable "stop", buried a little bit down the front (opposite) side of the throttle body, nearer the radiator. Take a look see, it's there!

 

I would first clean the throttle body and take a good hard look at the coils my two cents....David

 

Excellent. Thank you for the answers. I will follow up on both posts and see if I can't take care of it tomorrow. I've used Seafoam in the past to clean out the throttle body on our Volvo's any reason why I can't do the same with the Jag? I have carb cleaner so perhaps I'll use that first before using the seafoam. I've noticed that the throttle cable has some slack in it so I will pay close attention to it's adjustments.

thanks again,

greygoose

 

My 97 x300 just started to idle funky this morning, I started it up, let it come down to regular idle, put it in gear, backed out of the driveway, put it in drive, noticed a bit of a hesitation, didnt think much of it, drove through the neighborhood and came to the stop sign where it started to idle low and rough(never stalled though) Then I drove it back home, parked in the driveway, shut it off and instantly restarted it, then it ran fine, the roughness was only at idle, and never happened again, was this just a fluke? IAC stuck momentarily? Anyone else experience anything like this?

 

I had this problem with my '96 XJ6 when I first got it.
The issue was the IAC valve but in order to fix this, a whole new throttle body had to be bought.

At first we tried replacing just the IAC valve but I guess the valve and throttle body are "mated" together and mixing and matching them would cause high RPMs at idle. When I did this, my idle RPM was over 1400. The only way to fix it was either take it to the dealer to have it re-calibrated so that the throttle body and the IAC valve were mated again or find a used throttle body with the IAC vavle still attached. I did the latter and now idles smoothly at 650rpm.

 

If the IACV is the same as the "stepper motor" and I think it is, you have to recalibrate after replacing it, according to this page (scroll down a bit) AJ6 FAULT CODES AND IDLE SETTING / AJ6 Engineering

 

I went to the page and attempted to do the reset procedure as recommended but hit a wall when I saw step 7 which states-"Start engine and set base idle to 550 - 600 r.p.m. via air bypass adjuster" What is the air bypass adjuster?

 

I apologize for my delayed response.

You'll need an allen key, 5mm I think. The bypass adjuster is at the other end of the housing your IACV is attached to.

 

I see your engine block looks like the XJ40 block, is it the same on the x300? Also, can you post more detailed pics? Thanks!

 

Stalling like this is also symptomatic of a failing crankshaft position sensor.
How many miles on your car?
Check this out first; it's an easier and cheaper fix.

 

That procedure is not for the X-300.
The procedure that relates to the ISSC valve on the X-300 is a TPS calibration. The car automatically calibrates the ISSC position on shutdown and startup, but only corrects when the throttle is in the idle position, as measured by the TPS. So, the throttle plate must be closed, and the TPS must be saying that it is in the closed position. Make sure the throttle is indeed getting closed, and if it is, then consider getting the TPS calibration done by someone with the dealer level software.

 

Sorry folks! Dunno what I was thinking....that pic is indeed an AJ6, not the AJ16. I should stick to my own section.

but i miss my xj6

 

If, after reading my post directly above this one, you would still like photos...please tell me of what and I'll get them

There may have been tequila involved (on my end) in my attempt to be helpful with greygoose's problem.

 

Let's be careful here. We need to be sure of the engine management system we are dealing with. Those procedures at AJ6 Engineering are for the Lucas 15CU system in the XJ40, not for the X300; it has the GEMS 6 EMS system.

The only way to 'recalibrate' the throttle body or IAC on the AJ16 engine is to use the diagnostic equipment to 'Reset Throttle Adaptions'. That resets the base air and the IAC. The 'base air' is the amount of air that goes around the throttle butterfly when the throttle is closed. The ECM has to account for that fixed amount of air. That's why messing with or even cleaning the throttle body screws up the idle speed. When you clean the bore you instantly increase the base air and the idle goes UP. Then the ECM needs to be reset to account for the new base air amount.

Many stalling complaints can be also eliminated by the throttle adaption reset.

And you thought is was simple!

Cheers,

 

So I am taking my car to the dealer on Monday, they had attempted to do what I think is a reorientation but failed to do so the last time I went because one of my 02 sensors was defective. I have since replaced the defective sensor and am ready to go, I just want to make sure I am asking for the right thing?

 

Ask 'em for two things.

1. Oxygen sensor orientation.

2. Throttle Pot Adaption.

If they are unfamiliar with that test, have them find Bulletin 3.1-15. Step 31 of that bulletin explains it. Actually, if they run the orientation, it will be listed on the same page where they selected it.

Good luck!

 

I just dropped mine off for an orientation at the dealer, wish me luck! I hope this fixes it!

 

What about the throttle adaption??

 

So I got the car back from the dealer and they did the o2 orientation, I am not sure if they did the tps one but the car is still stalling out on me!