Yea, and oddly the parts stores said it was a rubber O ring and sold me one that IS the same size, but what was on it was a metal-film gasket but it came off clean so I wiped it off good and sprayed a little copper-coat on it and re-used it.

 

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Does anyone know the size of the two bolts that hold on the IACV along with the ID and OD of the special washer that goes on it?
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My dad was over and kinda helping me and we was checking it and the metal washer that fits so snug on it (and into a grove on the throttle-body fell off. We searched and searched and never could find it, then later realized in our rush to look for it, now we can't find those little bolts either so now have neither one and even if I spend an outrageous amount for a new one (when the old one we determined seems to be functioning properly) it wont come with the bolts even if it does come with the washer.

Second question, does everyone's IACV have a fairly thick gasket? My dad thought it odd to have such a precise machine fit and a special tight fitting washer, and then also have a fairly thick gasket too. Even without the gasket or bolts or washer, he just held it in place with his hand and I started the car and the idle was normal. He's wondering if someone didn't replace it at one time and the replacement came with an unnecessary (or at the very least unnecessarily thick) gasket which is holding it out too far even when it moves the plunger in all the way. Meaning it could be working but due to too thick of a gasket, it may still be letting too much air through.

 

Does the gasket look like this?

New Jaguar XJS Idle Air Control Valve Gasket JLM11490 | eBay

 

Yep, I can't tell the thickness but that's at least the colors, black on one side and green on the other. Though I noticed many of the replacements come with an O-ring.

 

Well, got the kitty back together. List of things done;

1. Removed (Properly) the secondary air-injection system. Like it was never there at all.

2. Replaced the Thermostat. Even though a test later in water on a stove shows that the original was opening and closing at it's prescribed temperature range.

3. Replaced the temperature sensor that feeds the ECU (not the single wire one that feeds the gauge).

4. Replaced the little metal washer on the air control valve (aka throttle kicker) with a rubber o-ring since we lost the little fitted metal ring. Replace the screws with allen head screws so I can take it in and out WITHOUT having to loosen the whole throttle body. The valve itself is still the same one I had to begin with.


After that she was idling slow, very slow in fact and I had to give it some extra gas until it got warm because it didn't want to idle well cold due to trying to idle so slow, once it was starting to get just a little warm, just enough to where it would idle on it's own though only just barely I then turned the air-bypass screw out until the idle was where it belonged. For some reason it had previously been screwed all the way in until it was bottomed out.

A 36 mile test drive and she got better gas mileage than she has ever gotten, I always wondered why this 4.0L cat gets worse gas mileage than other 4.0L models that I have had in the past. This one has never gotten over 24-25 and I have had both '94 and '95 4.0L models in the past (though the '94 was an AJ6, not an AJ16) and both would routinely get 28-33 on two lane highways. That's always confused me about this one since it's actually 1/2 the miles of one, and only 1/3 of the miles of the other that I had before. Anyway, the test drive now showed 32.6 on this one. Now that's by the little computer in the dash but I have found them to usually be pretty accurate on these cars out on the highway (only a lot of city stop and go idling seems to throw them off and even then not by much).

During the test drive I stopped several times, even got out at a couple of places, one of which she sat cooling down for about 2 hours. And she started right back up and idled perfectly again afterwards each time.

Of course the only problem is that I changed the thermostat, the temperature sensor, got rid of the secondary air system (wow, love the engine bay without that in the way), and changed the metal washer on the IACV to a rubber O-ring. So I don't know which item fixed the problem. It maybe a little less that it was the thermostat itself though because my fast idle was excessive even when the car was cold, i.e. not only was the warm idle fast, the cold idle was excessively fast as well. Plus testing the old thermostat in a pan of water afterwards shows it was working correctly and it was perfectly clean (no corrosion, etc).

 

Wow. Congrats!

I'm thinking the IACV gasket had failed! That's a new one. Glad you spent the time to get through this. I wanna make sure I'm clear that you did not replace the IACV itself.

Can you share the thread and size of the Allen screws you used for future reference? I will likely replace my screws someday, so I too can replace the IACV without having to loosen the throttle body.

Did you size the washer? I have a spare that appears to be 24mm on the outlast and 20.2mm on the inside. Does that sound about right?

 

SouthernGypsy, did you get your idle problem fixed? How, if you would please tell us.
RagJag

 

The gasket for the IACV looked great, in fact I am re-using the same one, but got rid of the little washer in favor of an o-ring which I noticed the new ones come with when you look at pics online.

The bolts I used which I like a LOT better then the 5.5mm stock bolts are Home Depot part number 887480032383 "Metric Socket Cap 4x16" MTSCKTCP4X16. Two in a package for .56 cents...

Everbilt 4 mm x 16 mm Alloy Socket Cap Screw (2-Piece)-803238 - The Home Depot

And I used two small star washers that fit snugly on them, though the lady at the counter couldn't get them to scan so just typed in "Misc Items" and charged me .20 cents. So I don't have a part number for those.

The star washers I used look like the smallest star washer shown in this assorted pack picture but the pack I bought had 8 and they were all the same size. I had already found the right bolts so just tried different sized star washers until I found some that fit the shaft of the new bolts snugly and the outer diameter was only slightly bigger than the head of the new bolts.

Trades Pro Lock Spring and Star Washer Assortment (720-Piece)-835795 - The Home Depot



Yes, I reused my old IACV and also ended up reusing my same old gasket since even though it seemed thick it appeared to be stock, and was in perfect condition. The only other thing I changed with reguards to the IACV other than the bolts was to use an O-ring... we have a large assortment kit in our shop and I just found one that fit snug and looked like the ones shown in the pictures of new IACV's online other than the one I used was black and in the pictures they are red.

I don't think the IACV gasket was leaking as good as it looked, maybe it was and the O-ring helped seal better than the original metal washer, but I don't see why the gasket would have leaked because it looked perfect. I only used the O-Ring because we dropped and lost the original little fitted washer. We also temporarily lost the screws which gave me the idea of getting some new ones that would allow me to remove/replace/test the IACV without having to loosen my throttle body or anything else. So even though we found the original screws I still went with new screws.

 

Well, Like I mentioned in my post I did a few things so don't know exactly which one fixed it. My personal suspicion is that it may have been more than one single thing.

I have a suspicion still that it had at least partially due to the secondary air injection system, once the motor stopped running after about 40 seconds when the car was first started, that system was then allowing at least some exhaust gases back into the air-box (the one-way check valve was clearly starting to fail). That may have been either enriching the air with more un-burnt fuel, OR, maybe the exhaust gases was making the computer think that the engine was starving for O2 and the computer was trying to compensate by raising the idle.

My second suspicion was that the temperature was either too cold or the computer thought it was too cold. We tested my old thermostat after we got it out and in water in a pot it worked ok but who knows, it could have been sticking and us removing it caused it to start working again. I've seen that happen, a thermostat that's clearly stuck closed or open in the vehicle then works perfect once it's outside. Just the act of removing them sometimes frees them up. So maybe the thermostat... OR ...maybe the thermostat was working correctly but the temperature sending unit was just not reporting the correct temp to the computer. This is a suspicion because I only put in a new sending unit for the computer, I did not change the one for the gauge, yet after changing the thermostat and the sending unit the gauge (still using it's original sending unit) is only registering a very very tiny increase which could be explained by going from the stock 188 to the replacement 192 degree thermostat. Plus the car had great heat even at the times when the OBDII was reporting that the computer only thought the temps was in the 170 range. On a cool night a car really running only 170 around here would probably not put out great heat in the cabin but this one could melt you. So who knows. It's just one possibility.

 

If removing the secondary air system would give my car anything near the mileage you are getting I would do that. My car only gets about 22-23 mpg on the highway. 15 is the norm in town. Glad you got your engine running well again.
Cheers, RagJag

 

Your getting just a little less than I was before doing this. Which was the worst I have ever gotten from a 4.0L so all the work was worth it.

Are you sure your one-way check valve is not allowing some of your exhaust back into the intake air-flow once the pump stops running? Mine was; at idle it was only just barely preceptable but I'm sure going down the highway it was worse. I think my one-way valve must have only partially failed (or maybes that's all the flow you get at idle when it's failed).

I'm lovin' having it off. The pump even though it was electric and not being run by a belt still took up room and blocked air-flow through that side of the engine bay. Once I removed it I can now MUCH more easily get to my alternator and be able to check the belt, reach the belt tensioner, etc. Plus I can easily see more air can now flow though that area under the hood, which means less heat build-up on that side of the engine bay which is the side the air-box, throttle-body, etc. are all on meaning they will stay a little cooler meaning air going into the engine should be just a little cooler.

Plus now don't have all that plumbing for it (including that check valve itself sitting under the intake manifold) running around the back of the engine and around to the right side of the engine going into the exhaust manifold. Meaning more room, better airflow under the intake manifold, and no extra heat from the exhaust manifold flowing back through all that piping.

On my '96 AJ16 engine it was SUPER-EASY to get rid of the pump and it's brackets, remove the rubber hoses, cap the hole in the air-box, and remove the pair of tubes on the right side that connect to the exhaust manifold. Then cut off those nuts, pull out the lines, and weld the hole in the nuts closed (paid the local muffler shop $5 to do that for me) and then grind the weld down flush. The hardest part was getting the pipe out from where it U's around the back of the engine. Originally I was trying to save the pipe and then said screw it and just got in there and cut it on the left side corner and a cut half way up the left side under the intake manifold. That made getting it out easy. I still saved the pump itself which was still good, it was just my check valve was bad anyway so was no need to save the check valve. The even though much of it was more or less hidden, it still makes the engine bay look cleaner without it. Especially around where the pump itself was. I was glad the brackets for the pump was just under two of the waterpump bolt heads and not like part of the alternator bracket or something like that. So once you removed them it looked as though they had never been there. I just backed out the two bolts that held it to the front of the waterpump and then put them right back in once the bracket was out from under them. The waterpump gasket (I think it's more or less like a big rubber gasket without any sealant on it) dribbled just a little but sealed right back up soon as I put them back in.

 

I will take and post a picture tomorrow of what it looks like now.

Do these in England have the secondary air injection system? The car REALLY does look so much more "natural" without it and the whole thing just seemed like something that had been added later, like for the US models. For example, the positioning of the alternator belt tension adjuster now actually makes sense without the air-pump in the way.

 

This is the EGGZACT problem and idle high and free run speed I'm experiencing with my 96 XJS. Dis you get this sorted out and what should I do? What about finding the PDU tool... any for sale? Any mechanic in mid-east coast Florida have one... Tampa Bay Area?

 

BuzGuy, I fixed my '96 4.0 from idling fast by installing a new EGR valve. Southern Gypsy fixed his by doing something else. See his post about fast idle. Apparently several things can cause this.
Luck, RagJag

 

Appreciate your note about an EGR valve replacement. May I ask did you have to reset any engine computer settings as discussed under PDU scan tools? Where did you get the new valve and how much should it cost?
Thanks much,
BuzGuy

 

Go back to the second page of this thread and read the posts. Oct 16 and 17 are the relevant on that I posted. Read all the posts on this thread because apparently there are more malfunctioning components that can cause the high idle.
Luck, RagJag

 

I just used my regular OBDII/OBDI/CAN scan tool (Actron model CP9690 Elite which I very highly recommend, they list for $375 but you can get them new from Amazon for $230 or sometimes even cheaper used from eBay and they are awesome) to tell it to clear all the codes in the system, even though no codes were stored I still told it to clear them anyway, and then I disconnected the battery cable overnight, also making sure to act like I was trying to start the car once while it was disconnected (working the ignition as though you was trying to start the car and holding it there for 10 seconds with the battery disconnected makes sure to drain any residual energy from the systems on many vehicles). Some people say you still need a shop to reset the computers on these but doing both of those together worked for me, may not work in every case.

 

Can y Actron pull ABS codes for the car? I have a cheapir $15 Actron, or a knockoff, and it only pulls the C level codes, which is what I need most of the time. It will not pull ABS codes, nor will it do any graphing, but there are apps and programs for that.

I bought Yhasi Movi Pro, which was the only prgram that worked on my Mac. It works great, graphing, pulling the same codes as the cheapie scanner. That program cost me $50, I think.

I also bought a knockoff Mongoose, which does pull ABS codes and does some of the Jag specific stuff, like resetting TPS and oxygen sensor reorientation. Its spotty, in the sense that I have to connect several times to get all the functions to work, but it's already paid for itself by identifying a troubled ABS sensor. I was able to remove it, clean it and voila! That cost me $150...which is what any shop charges me to hook up this car to their PDU/WDS/etc.

The advantage of your reader is that it is all self contained and portable. To run my stuff, I have to have a laptop, with the exception of the cheapy reader and my apps...I don't seem to like any of the apps though.

 

I haven't had any ABS trouble on either of my cars but it ask me about reading the ABS module as one of the options when I plug it into the '96 but not the '95. But I have noticed the '95 has a lot fewer options than the '96 inside the readers. I used to have a '95 that didn't even have the port so think only the real-late build dates even had the port in '95. My dad has a cheaper ($60) Actron as well as two other brands and they never ask about the ABS on these cars, though do on vehicles like my '04 Dodge Ram. It's only my newest Actron with the color screen that ever mentions it on these cars.

 

Can you do me a favor and ask it to read the ABS codes and see what happens? I assume it will either (a) tell you no trouble codes are present or (b) tell you it can't read it/error/etc