Hello everyone, first a short introduction since i'm new to the forums. My name is Marco, 32 yo and I am from the Netherlands, and since a month or 2 proud owner of my first Jaguar X-type 2002 2.5 V6 Petrol with 181k kms on the clock.

That being said, when I went too buy the car it was showing up the P0174 fault code, at first I was thinking about a problem with one of the oxygen sensors. But after reading a while on the forum here it's clear to me that the most likely cause is a vacuum leak of some sort.

Strange thing about the code is, it only shows up at highway speeds (120 kph), and very random, not even every day.
Car goes into some kind of limp mode because I can't accelerate beyond 120 kph and 3k rpm. Car starts stuttering then, until below 120 kph and 3k rpm, I guess this is normal with the code?

I already did the following:
- Inspect all hoses on cracks etc (also got the ribbed PCV hose mounted);
- Inspect brake booster & the other vacuum line on top of the intake manifold;
- Replaced the IMT valve o-rings (still had the yellow ones inside, and a lot of gasket maker);

Next thing I suspect, because it's only showing on bank 2 is a blown upper or lower intake o-ring, and someone has been using a lot of gasket maker there, so maybe that started leaking again. So I've ordered the o-rings and they will be arriving in a couple of days.

I've added some pictures of the freeze data when the fault occurs.

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What are you're thoughts about this?

 

MarcoB, do you smoke or have a friend that smokes? If so, get a nice cigar and smoke it, but gently blow the smoke into the engine bay with a cold engine. Make sure to blow the smoke across the top of the engine. What you are looking for is the smoke to make a sudden direction change. That will point you to your vacuum leak.

Before you do the smoke test, I would tell you to check 2 more things. First being the PCV hose running next to the throttlebody. From the sounds of things, you may still have a smooth hose there (going to be about the diameter of your thumb, running to the left o fthe throttle body). First off, is this hose smooth or does it have a pattern on it? IF smooth, pull that hose and look on the back side. Odds are, you will find a long split in the hose. Replace the hose. If you have the hose and it is not split, replace it anyways because if it isn't failed now, it will fail in the near future. If you have the hose with a pattern on it, then you have the upgraded hose and that should be good, but it can leak on you. So, look for that to be a point for leakage.

The second thing you want to look at is the vacuum line running from the top of the intake over to the brake booster. When you get near the brake booster, you will see a bulge in the line (we call it a football, it is really a check valve). Take your thumb and rub that bulge/football. Do you get a little bit of black dust coming off of it? If yes, replace that line. Does there appear to be a crack in it. If yes, replace. This is a common failure item along with the IMT o-rings and the PCV hose. We commonly refer to these as the "Big 3".

If all of these Big 3 parts check out, then odds are, you are looking at the intake gaskets being your issue. I would tell you to order both the upper and lowers. Based on the mileage on the car and the apparent maintenance (or the lack there of) done on the car, those o-rings are going to be your next likely suspect. Your local auto parts place will have a kit with the upper intake seals for around $30 USD. Odds are, they will tell you that they don't have the lowers. Yes they do. Tell them you need the lower intake o-rings for a 2002 Lincoln LS 3.0L motor. They are the same parts. Again, about $30 USD. When you do the upper o-rings, you are a few bolts from doing the lowers too. Bite the bullet and do both. Yes, it is a little bit more money and a little more time, but it will save you a lot of time later from having to go all the way back in to replace them later. Plan on spending about 4 hours pulling the intake, replacing the o-rings and then putting them back together. Not a hard job. Having a friend helping will make things go by faster.

 

Thanks for the tips Thermo, will preform a smoke test this week on the mentioned parts.

Here is a photo from the engine bay, which hose are you referring to as being the smooth one?

 

The chequered pattern one on the left is the one Thermo was referring to. You have the later up-rated part fitted already (patterned not smooth).
Still worth checking that for any defects, but far less likely to have failed.

The top right of your picture is the other vacuum line with the "bulge" in it that Thermo was referring to.
I see someone has previously been hunting leaks- the presence of some tell-tale goop that has been applied to the push fitting of one of the other visible vacuum line connections to the intake manifold just after the throttle body.

Also check the short large diameter air intake "accordian" pipe that couples between the solid air intake pipe (where MAF sensor resides) and the throttle body.....they can develop a split in the ribbing or the hose clamps might not have been seated or tightened correctly which can cause false MAF sensor readings.

 

Alright guys, thanks for the tips!

Gonna check everything again once the o-rings arrive, curious what i'm gonna find underneath the air intake tbh. ill report back once there's an update

 

MarcoB, if you find a bunch of RTV and whatnot there, go to the hardware store and get some abrasive pads (aka, greenies). These come in a few different colors indicating their courseness. Stick wtih the green or a darker brown as these are the fairly mild abrasive pads and will remove the RTV in no time flat, yet not scratch up the surfaces where you cause damage. But, get rid of as much RTV as possible. This will ensure you don't have a high spot and cause a leak.

 

Alright guys, time for a little update on the thread.
So last few days I've been busy on the Jag, looking for the possible cause for the P0174 code.

So first I've started disconnecting all the connectors and vacuum lines and what not from the air intake manifold, inspecting each line/hose after removing for cracks etc. CONCLUSION: NONE FOUND, all lines and hoses look good and show no cracks or signs of old age.

After that I've removed the upper air intake manifold, seeing that someone else had been busy hunting down this fault code, the o-rings were full of black gasket maker (color of the rings was yellow, original perhaps?) But there were no indicators of something leaking here, I was looking for maybe dry/dirty or oily spots.

After that I decided I should take out the lower part of the manifold, that was actually the easy part haha.
After I got it out I noticed a difference between bank 1 and 2. Bank 1 one completely dry on the surface, while bank 2 had a lot of oil (condensed carter fumes) laying all around the intakes, even outside of the o rings.. So my conclusion was that if a lot of oil gets out, air must come in here. Same for all 3 cilinders on this bank, all wet. The one on the right seemed the most wet of them all.

So fingers crossed today, build it all back yesterday and even replaced the bank 1 sensor 2 lambda probe because this also was giving a fault code. Gonna take it for a spin today, hope it will have done the trick!

Some photos:

Upper air intake manifold o rings

Upper air intake o rings, with a lot of gasket maker around them xD

Lower air intake manifold o rings (new)

You'll hear back from me in a few days, if everything I did as described above works!

 

Guys, a little update from my side.

Been on a camping trip to Luxembourg with the Jag, drove for about 700km total combined highway and scenic routes.
So far so good, no more fault code has shown. The throttle seems more responsive, RPM goes up smoother without hiccups.

Drives as an absolute beast right now, also my average petrol usage seems to have lowered as well, as I should expect when solving this problem.

Hope it stays this way, if anything changes i'll report back on this post.

 

MarcoB, good to hear that you found the issue and now can enjoy the kitty. If you have driven 700 km and no issues, then you should be good. That is a pretty good road test.