Hi there. We have a 2001 S 4.0 w/ 30K miles. I originally had a rough idle miss fire at idle and low speed. Read about many posts regarding the windscreen leak. I posted my solution which was to reseal the windscreen and posted pictures. After a water test the car was leaking still at the 4-5 1"x 2" screw covers. I sealed these shut with silicon. Retested.

1. So for the first rough idle repair, I changed all of the COP's and plugs. Orig. plugs were rusted on the outside portion. Indicating water present at some point. No oil was present in the spark plug holes.

2. Silicon sealed the COP covers back on with 100% silicon. Including the back were the wires go in.

3. Completed the above water sealing.

4. Rough Idle gone. Car ran perfectly.

5. Rained a few time plus a few trips to the car wash.

6. Water was leaking through the 4-5 screw caps above. Also sealed the Psgr side Windscreen wiper. There is a round rubber seal under the dash, accessable from the engine side. This LEAKS RIGHT DOWN ON THE DRIVERS SIDE OF THE ENGINE AT THE REAR. I have now sealed this also.

7. Sealed those. Tested with water hose. NO leaking into engine compartment.

8. Cleaned Mass Air Flow sensor with CRC MAP. Cleaned Throttle body cleaner with CRC Throttle Body Cleaner. All of this looked very clean to begin with. Cleaned it anyway based on threads and to elimin a simple item. Removed AAIC Air Assisted valve used at start up. Cleaned with the MAP cleaner as there were plastic parts in there. This did not look very dirty to begin with. Quite clean. This part only affects primarily idle. Does nothing after engine is at temp.

9. Ran Centech scan tool. No error codes hard or potential.

11. Is there something else which gets wet aside from the COP's and plugs?

12. Car ran fine for 1-2 months, seems like after the rain it began again.

Thoughts or solutions would be appreciated. I suppose it is possible water could have snaked up the harness into the drivers side even though sealed with silicone.
UPDATE today: 11/1.
1. Removed Drivers side COP cover. It was absolutely waterproof sealed tight. Removed rear COP Replaced with another (Orig) no change. Ran engine disconnected COP while running. Ran worse, so have to assume it is working.
2. No improvements. Except that after a real good warm up it does it less. Cleaned MAS, Throttle Body and AAIC valve. No change to rough/idle/miss. The car seems to shake and or miss every 45 sec to 1.5 minutes. You can see the RPM guage slightly move down a tick then back up.

Thoughts anyone?

John
Thanks, John

 

Hello there fellow Jag owners. I have not had a reply yet to my post below although 50 come have looked at it. Maybe you all do not experience this issue. Any how here it the latest update:

1. I was convinced that it was NOT the COP's, plugs, water and such as I replaced all of these. Had an improvement and then back to the same idle miss, unsteady rpm.
2. I read a lot about the Ford 3.9L same engine in the LS as well as the Jag, and use of the same in Ford light trucks. Same idle stall, low idle control issue.
3. How many have replaced the Idle Air Control Valve?
4. I just did so with a low cost solution.
5. First impression is steady needle in Park, R, N, and Drive. Rev of RPM's up and down I get the same steady idle at about 750.
6. Hoping to test drive next week and I'll follow up with the forum and let you know the results.

Thanks for all the forum inf. It's very helpful as I'm a new Jag owner.

John B.

 

Hardly any S-Types have the valve so few here will have had it fail - yet! As the cars age.....

More common failure seems to be the chain tensioners due to not changing to the metal-bodied kind. Again, we'll see more of these and it's likely a terminal failure.

 

John B., thanks for posting up your solution(s).


In all my years on the board here, I believe this is the first I have read about an "Idle Air Control Valve". Thank you for enlightening me. Just where is this valve located? Sorry I am bit to lazy to search .

 

I think it's known by some parts of Jaguar doc as AAI valve (AAI = Air Assist Injection) - e.g. see Fig 03.1 of the Elec Guide for the early cars.

I reckon the better PCMs and O2 sensors etc on later cars meant it was no longer needed.

 

Hi there. The valve is located in front of the air alum intake . Metering butterfly manifold. Just aft of it are 2 plastic hoses which go to the left and right banks intake manifold. The valve allows either more or less air into the engine at idle and cold primarily. I'll post a photo of the new and old part. It is a Duralast part TV 284. But I'll double check. 49. At Auto zone. I bought it as an educated guess baser on my research. This is a problem area on the Ford 3.9l and jag 4.0l. Engines. It is also used other Ford v6 version of the same generation engines. The valve is not cleanable. I tried.

John

 

Correct. The IAC went away when Jaguar upgraded to the electronic throttle body on the 2003 and up cars. This broke the connection between the gas pedal and the position of the throttle on the engine. So now the computer used the throttle body as a combination idle air control and throttle as well as a speed/RPM limiter. No need to cut the fuel or the ignition anymore.

The IAC is actually a problem anywhere it's used as they gunk up and start sticking. Glad they got rid of it!

I find my STR is very smooth at the limits now because of that. Try it yourself. Floor the gas pedal when the car is at idle. It just floats up to the limit and stays there no bucking and missing like the old days when the fuel and/or ignition had to be cut off.
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Hi there. So I replaced the IDle control valve. Engine idle changed somewhat more steady. However still a miss or flutter at idle. Otherwise runs well. I unplugged the new valve and engine nearly dies. So it's working. The old one did nothing by disconnecting the IAC.

New is a whistle sound coming from around the intake this valve or the throttle body. This would seem to be an air leak.

Listened to the exhaust. Seems like stalling is on the drivers side.

Recall all new cops plugs, water sealed tight. Thoughts on what intake seals may be leaking.



Took it to an independent. Said it ran fine no codes. He did finally say it did stall miss once as he drove it back to the shop.

So seem intermittent an most noticible when cold but also does same at temp. Any thoughts appreciated. 4.0 2001 s type 30 k miles. John

 

Duralast part TV 284 IAC .This part does not work! And it is slightly different. Don't use it. It is on the LS Fords. Idle Air Control valve. It causes a High Idle!

 

So question. What is the "Whistle" sound in the intake system. Showed up with a new Idle Control Valve or IAA.

Tried carb cleaner on all vacc and air line fittings and around intake manifold, with no changes in rpm. So, seems to be a small leak causing idle problem.

Your thoughts are appreciated.

John

 

Any air leak at all will cause problems and just needs fixing. The indy sounds poor as he should have found it.

 

Hi there. Any suggestions on air leaks? So, intake manifold, throttle body, to intake, any other gaskets? I can do it, just need the gasket list. I hear there are tricks and sealant req as well as torque seq in the intake manifold. Are there other bits which I should change if I change the intake gaskets.

Any ideas in the whistle at idle? Sounds like an intake leak however could be something different on this type engine.

 

There are many thread about leaks, best to read them for ideas.

 

Solution.

To summarize started with a rough idle/stumble. Miss fire could be heard but mostly at low RPM or idle. Occurred all the time even after warm up. See parts summary below:

1. Changed plugs and COP's. Used Mid range aftermarket COPs.

2. Car ran fine for a while.

3. Started stumbling again. Low and mid rpm.

4. Sealed window to be absolutely waterproof. Tested waterproof. See prior threads. It was raining in the engine compartment previously.
Car still ran rough idle/missing/car shaking at idle.

5. Solution:

A. Began changing out the 4 Drivers side COP's with the old ones. When got to number 3 (changing back to an original) it ran like a kitten. Left the 4th one in. So left bank 4 new ones, right bank 3 old originals and 1 new one.

B. Changed the Idle Control Valve.

C. Cleaned the MAF and Throttle Body with CRC cleaners.

D. All new platinum plugs.
Whoho! Success!! Purrs like a Kitten! I got it fixed after the car was with the Jag shop for 3 days. (I will say that the shop did not charge me 1 cent, as he felt he did not fix anything. In my opinion Honorable and honest. I'll likely go back.)

Parts x Reference:

A. Idle Contro Valve: AutoPartsWay.com: #OES1655566 Idle Control Valve & ESP1655729 gasket. This is labeled also: OEM Jaguar part AJ81325. The AJ81325 is the same part number referenced on Ford and Jaguar sites, as well as Jagbits. $263.45 including gasket and shipping. Info Attached.

B. Platinum plugs: Rock Auto: NGK 7090 Platinums $2.49 ea.

C. COP's from: Rock Auto: COP-13 United Ignition Wire. $21.89 ea. I'll return 1. (I'll let you know how this goes. They are pretty solid I do not expect problems.) Info attached.

Thanks Jagv8 and other contributors which helped me to "dial" it in. Frankly the retesting of the NEW COPs was a hunch, and was right. Plus the Idle Control Valve was bad, as well as the plugs.

John

 

COP info and Idle Control Valve info.

 

Hooray! Persistence pays.

(I don't know if those are the right plugs.)

 

Jag V8,
Hi there. Still purring like a kitten. There are many newer style plugs than original. See 2 shots attached from NGK's site. The plug looked identical to the one which came out. There is a cross reference to another part number.
Do you think this plug is an issue?

John

 

Not a clue as I stick to OE ones.