Engine Codes P0171 and P0174
 

Well I have these codes the P0171 and P0174 I know it's running lean and I searched on forums here found a lot of information and yes I checked my Brake Booster Hose and the middle plastic part looks good no cracks anything of that nature I checked my ribs hose that goes from the throttle body to the intake box and no rips no cracks then I check my PVC hose and again no rips looks good so I'm leading to think it May be my O-Rings or my MAF sensor cus I really don't know how to check that but the car is really sluggish and it stutters like it has no power when I accelerate the car and I did start feeling my brake pedal start getting harder to press I also stuck my finger where PVC hose goes to the manifold and there's motor oil so with that being said what parts should I start swapping I don't want to start guessing and waste money so what should I start swapping first with the information provided and yea I have a 2002 X Type any help? Or suggestions?

JagX02, I would first start with cleaning the MAF sensor. That is a $5 can of MAF sensor cleaner and about 10 minutes of your time. See what you have there. After that, I would say to get your hands on some tygon tubing (need about 3-4 feet normally) and put one end near your ear and run the other end near all the joints of the intake. If you have a vacuum leak, you will hear it in the tygon tubing. You can use a paper towel tube, but it may be a little big for some of the places that you will want to check. See what you find and go from there.

I did cleaned my MAF sensor I cleaned it the light came off and the next day sure enough it check engine light turns back on

Well at least let me tell you that you are not alone, these codes are super common and we've been through this with a lot of people. Just to be clear here is a pic of the common places to check

jaghelp.com: Jaguar X-type common vacuum leaks. P0171 and P0174

Just making sure you didn't miss anything. Also cleaning your throttle body could help.

Yes I checked the brake booster hose and the middle plastic portion seems fine and if by engine breather hose is the same as the PVC tube from the manifold to my intake box is shows no rips and tears and my valve seals also the O-Rings well those I guess I'm gona have to change those first then maybe try a new MAF sensor after that

With modern cars I'd read the LTFT values at idle & 2500rpm (parked, engine hot). If they're well off zero at idle and head towards it then you know you've truly an air leak. Other behaviour and you're wasting time looking for that and can study what happens/when. A cheap OBD tool like an elm327 is $10 up and much cheaper than parts-swapping plus quicker.

You guys think it's not my brake Booster cus my brake pedal is getting harder to press?

I just recently experienced these same codes and had a terrible time diagnosing the root of the issue. As it has already been stated, this is more than likely a vacuum leak of some sort.

FWIW, my leak was being caused by faulty intake manifold gaskets. If you have changed the spark plugs in both banks, you are familiar with the procedures. If you don't feel comfortable doing this yourself, I would estimate this to be about a $400 job including parts/labor.

Good luck.

First check the trims, then IF they show what is suspected chase why. But they may show something else and in that case changing parts based on wrong assumptions is expensive as they'd be the wrong parts!

I had these same codes on my x-type and it took me a while to figure out what was wrong.

After alot of research and troubleshooting... I did all the recommended things... starting with a new MAF sensor, checking all hoses for tears, replacing intake gaskets, fuel filter.... .

Next was a smoke test. I ending up pulling out the hose going into the brake booster and blew cigar smoke thru it to find out exactly where the air leak was. Slight smoke was coming out of the bottom of the intake manifold as suspected but there was a huge leak coming from a part that no one has mentioned... the right side of the throttle body!

I was gonna take apart the throttle body to replace the gasket but it had very weird screws (5 point stars) that none of the stores around here had tools to remove. So what I did was remove the throttle body from my car, used a tube of "gasket maker" around the whole entire edge where the smoke was leaking thru and let it dry overnight. The next day I put it back on and tried the smoke test again, and it worked. NO MORE LEAKS.

I have driven the car hundreds of miles now and I still don't have a check engine light or any more performance issues. Hope this helps someone in the future.