I'm about to put my S-Type up for sale but have an issue that I want to correct before listing it. During (only) cold days on cold starts it missfires on (codes thrown for) cylinders 1,3,5 for with the code for multiple cylinder missfires, Restricted performance and CEL read in the instrument cluster. I'm thinking intake gasket leak but wanted to get some professional advice before throwing time and money at the problem.

 

Does the car still have its yellow-colored factory Intake Manifold Tuner Valve O-rings? If so, that is often the problem. They fail, leak oil, and create a vacuum leak. The new-and-improved green-colored O-rings solve the problem, and are quite inexpensive. You'll need a set of two....

Search using the phrase "IMT O-rings replacement" and read all about it, including how and where to check for the oil leak. You can do this repair yourself with minimum tools. It seems that anyone with the 3-litre V6 engine eventually has to do it....

 

Don't know what color orings it has but I do know that they are leaking cause I see traces of oil on the valve cover driping down to the exhaust heat shield, But I've had this missfiring issue way before They were leaking. The colder the weather gets the wors the missfiring feels. The missfiring issue started last year (wasn't a member at the time) about the same time this year during the warmer months I had no issue with it at all. Thanks for your in put on the o-ring seals I'll be replacing them as well.

 

can any one else lend me some advice? I'm wondering why It misfires during the cold months on cold starts, cold starts during warmer or less colder days it starts up just fine? Coolant temp sensor maybe?

 

The seals will contract and expand with heat and cold so maybe it was hot enough that you couldn't tell they were leaking visually but they were. And, as it get's colder, you notice it more. Just a guess. Change them and see what happens.

 

Have you pulled the plugs to see if there is any oil on them? I had to have the spark plug O-rings replaced for this.

 

I doubt it because I replaced those not even a year ago, Havent had time to do the IMT valve seals just have it sitting in the garage for now, I did find that the rectangular thing on my intake pipe had a tear where they are conjoined, sealed it up with some gasket maker, might have been the cause of the rough idle that I've had maybe even the misfires but havent tests driven it yet, will report back with the results.