Hello, I have a 2006 Jag X-Type that was getting a P2635 Code when I bought it.

The car jerked when switching gears and was a little uneasy with fast acceleration

Because this code is related to low fuel pressure I replace the fuel filter and the fuel pump. After the fuel pump replacement the car became a lot stronger.

The code however did not go away... So then I replaced the Fuel Pump driving Module with an aftermarket one from Autozone
This made the P2635 code go away and I was happy. The car doesn't jerk on acceleration or on gear changes.

But the car was a little sluggish not the kind of power I would expect from it.

I got a new code P0420 which refers to the Catalytic Converter
and later on I received P0171 and P0174 codes later that day.

I am a little confused on what I should take a look at next, and I would like your help.

This is what I have tried so far:
-cleaner MAF sensor, which looks like an aftermarket one recently replaced
-new air filter
-checked for intake leaks (don't know how to do this properly... sprayed carb cleaner everywhere and nothing changes on the motors idle)
-hoses look like they are in good shape

Should I replace the Catalytic Converter? (expensive)
Should I check the fuel injectors or fuel pressure regulator?
Intake Manifold Gaskets?

-Thanks for your help

other than the check engine light and slower acceleration the car runs smooth. May drop in RPMs in idle on stop light every once a while

 

tgor, this is what I would recommend. The P0171 and P0174 are saying that you have a vacuum leak. I would look at the big 3:

1) brake booster hose that tends to have the check valve (football looking piece in the middle of the line by the brake booster) form a leak and the plastic will start to crumble in your fingers if you rub it.
2) IMT o-rings. These are located on the left side of the engine if you are standing at the front bumper. The o-rings are like $2 each and replacing them takes all of about 5 minutes
3) PCV hose. This is located just inboard of the throttlebody and runs from the front valve cover to the side of the intake manifold. This is known for splitting on the underside. Granted, since you have a 2006 car, you should have the upgraded hose which supposedly fixed this issue.

If these do not fix your issue, then you are most likely looking at intake gaskets. Before you replace them, I would say to get your hands on a good cigar (or buy one for a friend that smokes). Then what you want to do is light the cigar and with the engine cold and the A/C-heat off, start the car. Blow the cigar smoke gently into the engine bay, especially around the intake manifold. Watch the smoke and see where it makes a sudden direction change. That will point to where the vacuum leak is.

Please note that you have upper and lower intake manifold gaskets. If you are in far enough to do the upper gaskets, a few more bolts will get you to the lowers. It will cost you an extra $30, but better to do those than to have to get back into the car again.

Start with this and then lets see what you have then.

 

1. So I inspected the break booster hose and check valve, it looks almost new I can scratch it and it doesn't crumble (see picture) . Is it possible that I has failed internally?

2. I haven't gotten to the IMT O-rings, I have to look up the part number to buy at a local parts store, ill most likely do this tomorrow

3. The PCV hose is in excellent condition looks pretty new. However as shown on attached picture, there is a hissing sound coming from the top of the valve (where the purple arrow points), I have clamped it down harder and cleaned the connection and no difference... Could this be because of the amount of air flowing inside the valve? Should I worry about it?

I don't have access to a cigar and don't have friends that smoke. Is there another option that I could try?

 

Hissing indicates a big leak. (Obviously needs fixing.)

Even a tiny one - which you typically cannot hear - would need fixing, too.

 

tgor, if you can hear hissing from the PCV valve, then the PCV valve is bad and that is more than likely the cause of your P0171 and P0174 codes. Once you clear that, then the P0420 should clear itself too.

 

Ok I'll take a look at the valve, I can only hear the hissing through a tube running to my ear otherwise the sound can't be heard. The sound is only heard diectly on the top of the pcv valve and not anywhere else. Is it possible that the hissing is internal? Is there a way to test it once I remove the valve?

 

tgor152,

I just repaired 3 vacuum leaks on my 2002 X Type - see attached thread for what I did. The PCV valve was the source of one of my leaks.

May help, might not, but it is something to try...

https://www.jaguarforums.com/forum/x...-leaks-197756/

Good luck!!

 

So I removed the intake manifold and cleaned everything out and replaced gaskets. And now the P0171 and P0174 codes are gone.

The P0420 code came back, so I took off the old catalytic converter and it looks like it is in good shape... could the problem be something else?

How do I know if the old catalytic converter is bad?

 

See if they stay gone.

Maybe another cause of P0420. They're in the codes PDF / workshop manual.

 

So I replaced catalytic converter and tested the downstream o2 using propane...

the downstream sensor seems to be working. When the propane is on it the sensor outputs a voltage of around a volt and when I take the propane off the voltage drops to near zero quickly

I got the P0420 code again... also when I replaced the manifold gaskets i also replace the fuel rail with a used one from ebay it had the fuel sensors, regulators and fuel injectors

I also replaced the spark plugs... I'm running out of ideas... please help me... I'm starting to get disappointed with the car, I can't pass emmisions like this

 

tgor, I know you tested the downstream O2 sensor, but have you contemplated that the upstream sensor may be the issue?

In short, there are only 3 things that can cause what you are seeing:

-bad downstream O2 sensor
-bad catalytic converter
-bad upstream O2 sensor.

You have already replaced 2 out of 3. So, not leaving much else. If that doesn't fix it, then you are looking at a bad wire between one of the sensors and the ECU/ECM which should show itself when you are looking at the sensor readings (ie, large spikes).