danielsatur - even if sticky, which is doubtful, how would that cause a misfire?

Please post a properly detailed answer not just a few words.

 

A dirty throttle body causes 2 things, poor idle, and stalling both at idle and when on the freeway and you take you foot off the gas. What happens is there is no longer a mechanical air bypass past the throttle blade, and the idle air control solenoid in the throttle body which is normaly just as dirty, cannot comphensate fast enough. Clean not only the part load breather, but the throttle body bore and air bypass port(drilled port just above the throttle blade that comes out just below it.

 

Brutal - I agree.

That's why I asked daniel to explain how he believes it causes a misfire, especially one such as Jon89 has. (I don't believe daniel's right but let's see what he says.)

 

All that has been on recent threads here. But you have not explained how a sticky throttle can cause a misfire - please do.

 

That has also been stated.

Please just answer the question.

 

Many thanks to Brutal for taking the time to be as detailed as he has been in this thread. If and when the P303 misfire code pops up again, both Brutal and Rick have convinced me that the best possible action for me to take would be to go ahead and replace the two Intake Manifold Tuner O-rings with the new-style green-colored ones. I'll spring for new upper intake manifold gaskets as well - why risk not doing so? And I think I'll also go ahead and put in a new set of NGK iridium spark plugs. I've determined that my factory plugs are Motorcraft iridium plugs. That makes sense with the engine being essentially a modified Ford Duratech V6. The only thing I hadn't thought of that Brutal mentioned is to go ahead and replace the cylinder 3 coil. I haven't decided on this yet. Remember - when the cylinder 3 misfire (code P303) first appeared in early September, that coil was supposedly swapped with cylinder 2. Well, we had another cylinder 3 misfire (code P303) occur on October 2nd. If a bad coil is indeed the culprit, my thinking is that cylinder 2 should have been the one that misfired and threw a code P302 and turned on the "check engine" light. And that did not happen.

After thinking about and studying all this information for more than a week now, I think that Brutal and Rick have presented the best approach to me by replacing the Intake Manifold Tuner O-rings. Even my dealer's service department has recommended that this be done. And of course, they want to do it at my expense. But I'm leaning towards taking up Rick's generous offer for me to drive the car to his house (3 hours away) and the two of us will do the job in his driveway and get a chance to meet for the first time. That's a lot more appealing than continuing to pay a dealership that just wants to sell me multiple services with no actual diagnostics confirming that those pricey services will actually fix my misfire problem once and for all.

But unlike Rick's car back in March of this year, I'm not seeing or feeling any oil leaks down on the bolts or under the tuners. I don't think I'm hearing any vacuum leaks either, but I will continue to look for oil residue and listen for hissing sounds under the hood. But if our S-Type throws this same P303 code again in the weeks or months ahead, I think I'll order the gaskets and O-rings, pick up a set of NGK iridium spark plugs, confirm with Rick, and head down to his house at his convenience. I think we'll have a great time together and fix this S-Type's misfire problems all at the same time !

Additional information that may prove to be important for our particular car: The entire Throttle Body is new (May 2009), the Mass Air Flow sensor is new (October 2009), and the Air Filter Housing and Air Filter Element are both new (October 2009).

Other opinions and recommendations on this topic are always welcome. Those of us with the original Intake Manifold Tuner O-rings (which I understand are yellow in color) may all be dealing with this issue in the near future. I wonder what contributes most to the failure of these yellow O-rings - age or mileage?

 

well the old adage holds true in this case. "SIZE MATTERS!" the yellow are slightly smaller than the green and that green coating on the black oring seals to the intake, theyre very hard to remove once they set. And its not so much a matter of a vacuum, or oil leak but also a chance to install updated known improved orings and CLEAN THE OIL FROM THE LOWER INTAKE OPENING WITH THE IMT REMOVED. I personally would spend the money on a couple coils over new upper intake orings(not the IMTs but the intake seals) and theyre probobly cheaper

 

Brutal,

I thought your misfire theory centered around these factory (yellow) IMT O-rings failing, thereby allowing blow-by oil into the cylinders (primarily cylinders 1, 3, and 5), and thus causing the misfires that I'm getting along with other S-Type owners who are experiencing this same problem.

Now you seem to be saying that you would just replace a couple of coils instead of replacing the factory (yellow) IMT O-rings when you already know they create blow-by oil problems in the cylinders.

What gives?

 

The oil thread lists the wrong oil. It should be 5w30 semi-synthetic.

I wouldn't start the engine with a plug out unless truly desperate. YMMV.

You still haven't answered about the sticky throttle.

 

maybe i wasnt clear or you and I were drinking.... oil vapor as part of the crankcase breather system runs oil laden vapor from the crankcase through the intake. It collects on the inside of the intake manifold, as well as the throttle(why it gets dirty, and sticks) the oil inside the intake tends to collect in the lower plenum which feeds the A bank cylinders 1,3,5 in this case. This I believe to basicly oil fouling of the plug which increases resistance, makes the coils begin to run hotter, break down and find the path of least resistance. (the head) and arcs accordingly. this is why many times I see high voltage damage around the plug well opening when you take out the coil. Not always but many times, Just depends how long its been doing it. This has been a problem long before I started in the mid 90's with Jags. On my 96 it was so much a problem the throttle would be sealed shut when cold and you could start the engine, but not push the gas pedal, unless you broke it. The fix for this was a oil vapor recovery mod that seperated alot of oil from the crankcase vapor and ran it back into the oil dipstick tube to the pan. This is just my observations over the last few years. The reason I talk about the imt is because theyre a bad source of vacuum leaks
and oil leaks. The cam gaskets many times get blames for oil leaking on the exhaust and changed and not the IMTs. I have opened up intakes to replace imt orings and literally had oil pour out all over the exhaust. Is there a permanent fix? not from Jaguar, sometimes it just is what it is and would take maybe a redesign(wont happen) of the intake/engine. new engines are already out and time marches on...Of course these are all just my hypothesis, and maybe dont amount to more than thinking out loud. I just know what I do in these situations I have have very few recheckes for this issue. They do return, but is usually a few years down the road. about the same your seeing on a 3-4 year old car.
you know maybe someone could drill and tap the intake right there, install a line and catch can that would hold vacuum and could catch the oil and drain it out. Then you could market it on Ebay and retire in the Bahamas....

 

Brilliant.

(now, off to the Bahamas)

 

It is my understanding that Ford did NOT install any Intake Manifold Tuners in its Duratech 3-liter V6 engine that it placed in Ford cars. If the Intake Manifold Tuner is such a problem-causer with vacuum leaks and oil leaks on many if not most of the Jaguar cars that use this modified Duratech engine, why did Jaguar opt to include IMTs and create more problems by doing so?

 

imt's are very important for the best of both worlds, they make the intake plenum/intake appear smaller to the engine for better fuel economy and throttle reponse. And when you punch it they open making the plenum/intake larger for more power argh argh argh argh
it is one thing that really makes the engine behave like two different power plants. That and vvt's
orings are not a big problem, 2 generations of parts and they got it right with the green ones.
Without intake manifold tuning valves you really would be unhappy with the cars drivabilty and performance compared to what you have now

 

Thanks for the explanation, Brutal. It sounds as if once the new-style green-in-color IMT O-rings are in place instead of the factory yellow ones, the issue is solved. Rick's car is essentially a beta test for that, and our car probably will be as well before too much longer....

 

Don't you read any of the old messages?