I'm in a motel tonight on a trip so I have the car with me but my scanner is at home. I will be home Monday night and will be happy to try it for you and let you know what happens. If I forget before Monday just message and remind me again, I should be home Monday early evening.

 

RE: That's bizarre, Before you responded and after some searching I found a part number for a gasket which says it's for 96 model 4.0 throttle bodies. OEM Part # EAC9822.

So, what is the final verdict here? Gasket or no gasket? Maybe an optional gasket if you have leak issues? My 96 XJS has the exact same high idle problems and I need to know how to fix it. The car has only 12000 miles on it. Anybody want to rent or sell me the right tool to setup my problem part? What is my problem part? I really need help. Call me at 570-762-4972 or use buzguy@gmail.com if you like.
BuzGuy

 

RE: That's bizarre, Before you responded and after some searching I found a part number for a gasket which says it's for 96 model 4.0 throttle bodies. OEM Part # EAC9822.

So, what is the final verdict here? Gasket or no gasket? Maybe an optional gasket if you have leak issues? My 96 XJS has the exact same high idle problems and I need to know how to fix it. The car has only 12000 miles on it. Anybody want to rent or sell me the right tool to setup my problem part? What is my problem part? I really need help. Call me at 570-762-4972 or use buzguy@gmail.com if you like.
BuzGuy

 

I ordered that gasket but it didn't fit. Was close but two of the bolt holes just wouldn't align quite right and so what I did was spray a very light coat of COPPER COAT on both the intake side and the throttle body side (put a rag in the holes so none would get inside as I sprayed) and let it just start to get tacky and then installed the throttle body. Worked great. Copper Coat is a great item for situations where you have parts that was originally machine fit with no gasket but due to time and age may no longer be a perfect seal.

 

Thanks for the tip about that being the wrong gasket. I liked your copper
coat solution. Are you saying that copper coat was the thing that brought
your erratic Idle speed under control? Is this the illusive answer I've been trying to find?
BuzGuy

 

I don't know that it is what solved the problem as I did several things all at the same time and one of them (or a combo of them) fixed it. It certainly can't hurt and on an older engine is a good idea. I did not see any signs my throttle body was leaking before using the copper coat, but don't like the idea of no gasket at all and on a location like that copper coat is the appropriate solution in lieu of a proper fitted metal-film gasket made for exposure to fuel, you could cut a gasket from gasket material but it wouldn't be correct for a location where it was exposed to fuel.

Your talkin' an inexpensive can of Copper Coat, a great product to keep around anyway as it also serves as an anti-seize on bolts, etc. and a few mins to do, it so it's worth a try in any event.

I didn't have a new gasket for my thermostat housing so cleaned the old gasket and lightly sprayed both sides as well as the threads on the bolts with it also when I put in the new thermostat.

 

Thanks for the clarification BUT I almost wish you had not told me this. I guess I still haven not determined what to do about my fast idle problem. Everything with this Jaguar is so dam complicated, I'm beginning to hate it. I paid about $35,000 for this car because its just like new with only 12,000 miles on it... There is no recourse to the dealer available either. He practically made me sign my life away when I bought it.
BuzGuy

 

Buz,

There's a whole thread to go through here. There will not be a one size fits all answer.

Have you cleaned the throttle body?
Checked the voltage at the TPS at idle (should read 0.5v)
Checked the EGR valve?
Checked the gasket for the IACV?
Checked to see if you can do a manual reset of your IACV?

What worked for Southern Gypsy, didn't work for me, nor did it work for the OP, so it's unlikely to be the solution for you.

We can work with you, but you'll need to do a bit of troubleshooting for yourself.

If you wanna throw parts at it, you'll spend about $400 on a new IACV and EGR but it may not solve your problem. Let's start with rereading the thread and following some of the suggestions.

The easiest and cheapest seem to work in this order:

1. Try a manual reset of the IACV (instructions in this thread)
2. Check voltage at TPS
3. Check EGR
4. Clean throttle body
4b. Check IACV gasket

Ultimately you may need to take it to a Jag specialist that has a computer to reset throttle adaptations.

Start with those, basically free suggestions. If you know how to check for vacuum leaks, that would definitely be something to do as well...

 

What model is it?!?

Well, start by loosing the secondary air-injection system, or at the very least disconnect the hose from the pump to the air-box to make sure your not getting exhaust back through a bad check valve like I was (oh, and unplug the electrical connector from the pump at the same time). Removing the SAIS was actually the last step I did but turned out to be the one which afterward I noticed my idle wasn't high any more though could have been a coincidence since I had done several things about the same time leading up to this.

Copper-coat the throttle body to intake manifold

Change thermostat to a 192 degree from the stock 188

Change the EGR valve (I did but then changed back to my original later)

If none of that fixes it try the trick of taking out the IACV and with it uninstalled plug it back into the plug and have someone cycle the key, see if it moves in and out, if you get it to move to a position where it's really far out, put a new rubber O-ring on it (gasket goes on IACV first, then the O-Ring) and forget about the metal washer if he had one, unplug it, and then reinstall it but leave it unplugged and then see if the car idles lower. If it does then fine-tune with the air bypass screw to get a 600 RPM idle when warm in park. Disconnect your battery and leave it for an hour. Reconnect and start and see if it still idles at 600 RPM. If it does then re-plug the IACV and see if that changes it again. If it is idling correctly then your good (mine was good at this point). If it goes back to idling fast then take the IACV back out, and re-do the key off then on thing to make it extend all the way out, unplug the connector, put in the IACV, leave it unplugged and see if the car is back to 600 RPM and if it is then just drive it with the IACV unplugged.


Actually after all that I put my old EGR valve back in and returned the one I had bought, and mine was good with the IACV plugged back in.... However, had it not been I was prepared to just leave it unplugged once I got it in the fully extended position until I got my hands on another one.

Oh yea, and I had already checked my TPS and knew it was good.

 

Removing the check air injection should cause your check engine light to come on. The check valves do fail, but they are easy to get, it's a GM part.

The original thermostat is 88C, not 188F.

 

I may have mis-read the thermostat. No, it didn't set a code and my MIL light did not come on... but I had a code from that system last year and reset it and for some reason on these cars once you get the MIL light and code once and clear it, it never comes back again even if you totally disconnect it. I knew about that before I started. It's not just about the expense or how hard it is to find; it's a royal PITA to change, it's about easier just to remove the whole system.

 

I have entered my comments and questions within the quoted message and I hope the show up easily as intended. Thanks for your help again, BuzGuy

 

Post #26 covers the manual reset of the IACV. Try that and see if you can get the IACV to respond.

The TPS is on the underside of the throttle body. It has three contacts, I forget which of the two you need to probe with a multimeter, but you have a 50/50 shot of picking the right two of three.

Jaguar XJS Shop Manual Service Repair Book XJ s 4 0 3 6 6CYL Workshop 1984 1996 | eBay

That's a link to the service manual I use. It's not perfect, but it is mandatory.

 

According to what I read and heard from a few different people after that was posted before that reset procedure is only for AJ6 cars, not the AJ16's, though if the IACV is responding at all you can use it to find the fully extended position and just put it back in the car that way with the electrical plug disconnected which should then let you adjust the idle with the air by-pass screw and you can drive it with it disconnected if that works, but on AJ16 cars it's not supposed to work to actually "Reset" the IACV. At least that's what I was told by a couple of people on here and a Jaguar shop.

 

Again, I much appreciate the response from everyone. I wiil advise results. Its hard to believe that Jaguar does not furnish its dealers with updated tools/gauges, etc to maintain these cars. I know its a 96 but its an expensive 96 and the company should recognize that when making service decisions for its dealer equipment.

 

It'll reset it, just not permanently. It is a good test to see of the IACV is working properly. If you can't get a good idle from this procedure, then the IACV is probably part of the problem.

Once you turn the car off, your idle issues will probably return. I was never able to make this procedure stick, however it did confirm that it was working properly.

 

Vee:
I haven't tried that yet but I was looking for a tool and discovered something that might be important. As I said, I was looking for an original tool and ran across this. My car is a 96 and has the markings it is OBD II certified. This cheapo tool work from 96 onward so I got to thinking if this one does that then why wouldn't whatever they use at the dealership work with my car? I'm pretty sure its a safe bet whatever they have in the shop would be better than the cheapo tool I found... the key is that they could be for the same applications. See the reference below. If I am correct about this let me know and I will just reschedule my service appointment.
Thanks,
BuzGuy a/k/a Guy Giordano

> Fits Jaguar OBD2 OBDII Advanced Wireless Bluetooth Scanner Code Reader Tool | eBay

 

Dear Gypsy:
I should have asked earlier but now realize I do not understand the difference between AJ6 ans AJ16 cars. I should also note my car is a 96 that is OBDII compliant. So, I'm wondering the same as in my reply to VEE, if the current dealership instruments will work on my car? Again though what is AJ6 vs 16? Could it be 6 vs 12 cylinders?
BuzGuy

 

You can do a wiki search for AJ16 and AJ6 engines.

They do make computer equipment, I have a fake mongoose which can read and reset certain features in the car. That was $150. Most generic readers can't really get into the custom Jaguar features, so be careful.

There are Autoenginuity (I think) scanners that start in the $1,000 neighborhood that allegedly can be used. I'm not sure you're into that kind of investment. Google Mongoose Jaguar OBD.

They don't sell PDUs, nor are they easy to come by. You can google that as well. Your best bet would be to find a Jag specialist and go there.

 

AJ6 was the first generation aluminium straight 6 Jaguar engine, came out in 1983. Lasted until 1994 model year in Sedans, not sure about the XJS. The AJ16 came out in the 1995 model year. AJ6 has a distributor, AJ16 does not, it is coil on plug ignition. Your 96 will have the AJ16 engine.

What the dealer software does is resets the throttle position that the computer recognizes as closed throttle. Previously there was slotted holes in the throttle position switch so it could be adjusted to produce the required voltage at idle. The throttle position reset is needed after a throttle body replacement.

The newer system had no slots on the TPS, instead each car's computer was calibrated to the particular switch the car was built with so it knew what was closed throttle. If it doesn't think the throttle is closed, then the computer will not activate the idle air control motor to control the idle speed.

There is a thread here about duplicating the dealer software, and I have done it. Requires a special cable to connect to the car though. Chinese clones are available and have a high failure rate, or the dealer grade cable is about $600. The massive thread all about how to do it is here if you want to try it yourself: https://www.jaguarforums.com/forum/g...an-tool-66558/

Current dealer software should work, if the tech knows what they are doing to get it to talk to the car. It can be tricky sometimes. The procedure you want is a Throttle position reset; sometimes also called throttle body adaptation.

These 6 cylinder engines are common to have the throttle shaft gum up with oil and crankcase blowby, thus preventing the throttle from closing completely. Try turning it shut by hand ( sometimes forcefully) to make sure that "closed" really is physically against the stop. If it isn't, throttle body replacement is the only option, as cleaning doesn't seem to work and the parts are not available seperately.