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Richard, Jaguar Technician
Category: Jaguar
Satisfied Customers: 15311
Experience:  12 years at a Ford/Lincoln Mercury and Jaguar dealer as technician and shop foreman.
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2002 X-type: best approach in fixing a dtc p0430?..000 miles..stall

Resolved Question:

What's the best approach in fixing a DTC P0430? The car is a 2002 X-type a/t with 115,000 miles. On occasions, the car would stall during cold starts in the morning. It's also been going into closed-loop immediately after starting the car (still cold starts) when it does stay idling, but only at about 1000 rpm's (which takes a longer time to warm the motor up. The car used to rev higher upon start-up. Spark plugs, coils and seals were replaced not too long ago. Thanks!
Submitted: 4 years ago.
Category: Jaguar
Expert:  Richard replied 4 years ago.

Hello and welcome to


I think we have more than one problem. We most likely have a vacuum leak causing the rough idle when cold. The intake gaskets leak causing this. FOr the code P0430 the front cat converter will need to be replaced and the vacuum leak most likely caused the converter failure.

Customer: replied 4 years ago.
Relist: Incomplete answer.
Expert:  Richard replied 4 years ago.

We need to check for a vacuum leak first as this will cause the engine to run rough when cold. Start the engine and listen for any hissing or air noise from the engine on a cold start. I see you already replaced some seals but the upper and lower gaskets leak, booster hose, IMT seals and the orings at the bottom of the booster and purge quick connect fittings all leak when cold. The PCV tube also splits but you would have most likely already seen/heard that. Please lets check for a leak first. Then we can clear the code to see if the cat fault code returns.

Customer: replied 4 years ago.
All of the items you mntioned (PCV, imt rings, break booster hose...) have just been recently replaced, so that should eliminate vacuum leak. Would that be the only cause of a rough idle (sometimes to the point of engine almost dying) during cold starts? Like I mentioned earlier, the car used to idle higher at start-up before it started going bad. As far as the code P0430, are there any other steps I can take before I start replacing an expensive catalytic converter?
Expert:  Richard replied 4 years ago.
Were the lower intake gaskets replaced on the fuel manifold?
Customer: replied 4 years ago.
Looking at the invoice from the Jag specialist, It doesn't appear that the lower seals were replaced. I really doubt that my car has a vacuum leak. I'm still only getting a P0430 and nothing else.
Expert:  Richard replied 4 years ago.
I am leaning towards a leak. I think if you replace all the intake seals your rough run on cold starts should be eliminated. In order to check for a leak we use a smoke machine.
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