With the bypass valve open pressure (vacuum) will be equal on both sides of the supercharger and the sensor will see the same as what is in the intake elbow.

Sorry, I misunderstood your earlier post. Thought you meant it was connected to a port where it would only see vacuum and not boost pressure, which would not be correct.

 

This is a little tricky as fuel trims will vary as load changes. Best way to observe is on strait and level road with the cruise on. Start adding hills, aircon or a twitchy right foot and the trims are all over the place.

Having replaced all of these parts, have you done a hard reset to clear the messed up fuel adaptations?

At WOT the ECU does what is called WOT enrichment rather than a strait open loop control, so wonky fuel trims from down low still apply at high rpm.

You might try resetting them and then driving the car for a while to let it re-learn. At differnt constant speeds, say 10, 20, 50, 70, 90 you should see more or less the same fuel trim same as idle.

 

Ah ha, ok so yes at idle it was a vacuum leak, and with the bypass closed it would have been a boost leak. Either way glad I found it!

Yes i did a hard reset, battery cables off and touching together for 10mins.

I did some hard resets in the past before all these dramas (in addition to a couple of ECU re-flashes) and the car drove great straight away. Don't forget it's basically stock, nothing too wild.

Will have a look at the fuel trims while cruising, i'm done with WOT tests for now, the next one will be on a dyno with an exhaust gas analyzer hooked up.

I am hedging towards the cats being the culprit now, partially blocked and unable to flow enough at high revs = misfires.

One thing I noticed from the WOT road tests, is if I did two back to back, the problem was much worse on the 2nd run. So i'm thinking the cats hot from the 1st run, which made it worse on the 2nd. When it's on the dyno we can turn out the lights and see if they start to glow...

Also, new cats is a relatively easy thing to do (not cheap, but easy) and they were on my list of things to do eventually...

108'000 miles on the original cats...

 

The worse on second try part is interesting...

I am sure this came up before, but you are sure the intercooler water pump is running and moving water?

 

Yep, definitely have flow through the intercooler circuit, can feel it in the hoses and if I pinch a hose I can feel the surge when I release it.

 

Right.

 

You'll be luckt to get 0% trim! But near it & not much different when revved would be a really good place to be.

Blocked cats seem to cause weird trims and yes can be misfires.

 

Well the new PCV arrived, couldn't see any difference between the old one and the new one, neither of them seem to do anything, same sucking sound, etc...

Put the new one on anyway. Noticed now that the LTFT's at idle are +3%
Cruising on the motorway in 4th at 3000rpm, they are slightly negative.

The guys here with the Motorvac want $280 for a carbon clean. I picked up a can of that Liqui Moly upper engine cleaner and ran in through. Bit of smoke at the beginning, but not much after that. Cost me $15 cause I had a credit at the parts shop.

Has made no discernable difference at all.

So next thing is the cats. Car is booked in for next Tuesday, 100cell cats, they will make complete bolt-ins for around $950 Aussie (about USD $725) which is alot cheaper than the Nameless ones for USD $1249, not sure how the shipping costs would be from Australia to the US, but Namless quote $160 US to ship to Australia, would be about the same I guess...if anyone is interested.

EDIT

Forgot to mention, fuel pressure via OBD is showing 55psi at idle again, and goes up to 70psi at WOT. Same as before.

 

I had George Panagos from venom exhausts Products | Venom Exhaust Works | Performance Exhaust, High Flow Catalytic Converters make my 2 &1/4 in and out 200cell cats $300 including postage for the pair he put the 02 sensor holes in the front and the back so it was reading before and after he probably remembers me as I spoke to him on the phone for a while telling him what I wanted

200 cell are the minimum legal in Australia 100 is really for race only

I then had Trevor from CES racing Home-Custom Exhaust Specialists-CES make the pipes out of the headers

I stepped the diameter up to 2&1/4 inch all the way to the end of the merge collectors then just used the rest of the existing exhaust

Trev builds the headers I designed for the AJ16 engines for me and worked for Garry walker racing XJS cars in the old days he is probably the best in Australia

He gets cars sent to his shop from all over Australia

If you wanted what I have he could just copy my pipes I only live 60 k,s from him and he is building me 4 sets of AJ16 headers at the moment since the Aussie dollar has dropped I have had a few orders for them again LOL
I can keep an eye on the whole thing as I am in and out of his shop regularly at the moment

I also travel with my van to Melbourne every 2 weeks so could drop past your place to drop them of as well on my travels

I do a few deliveries in Sydney as well so nothing extra for me to drop them of
If that's of any help to you Cam

 

Hey Doc,

My understanding is that the N/A "front pipes" are different to the S/C ones, so direct copy of yours would possibly not fit.

The price quoted is to make up complete pipes, like the Nameless ones;



That price also includes fitting and time on the dyno, so if I was to just get the pipes made up without fitting/dyno time it would be cheaper.

I asked about 100cell vs. 200cell, they tell me from an emissions point of view there is little to no difference, and strictly speaking neither would be exactly legal if taken to the nth degree. "We only do 100cell these days" was the answer i got.

There is another X350 XJR here in Oz with 100cell cats already too.

It's easier for me to drop the car off in the morning and pick it up in the afternoon with everything done. And these guys have the dyno that I used previously so any tests will be proper apples with apples.

There will be a custom tune loaded into the car to turn off the DTC's for the downstream O2 sensors, as well as tweaks for fuel/timing

 

Cam sounds like you have got it figured out as I did when I did mine

The original cat,s in our car are quite restrictive 400 for N/A and 600 for S/C and they are old and probably a bit clogged if not fully clogged

If your car has ever run really rich it would have killed the ceramic style cats anyway
The N/A down pipes being different I have no idea

I know the headers are a crossover type on the N/A engines compared to the S/C engines if time was permitting it would be nice to pull the headers and check for any black sooting around the manifold head section then port them to make them flow a bit more I know the EVO boys port the standard manifold with good results

I hope this all sorts your problems its frustrating when something goes wrong with these cars not many people with the knowledge to fix them

That goes for a lot of these new cars am having problems with the wife's Jeep GC ecu sent the ecu to the states to be recoed and its now dead have had to buy a second hand ecu and put all my info into it a very expensive bit of kit and the thing is still not going after 2 months another storey for another forum LOL

 

I'm hopeful that clogged up cats is the issue.

Here is some interesting reading catalytic converter failure in boosted applications - www.fordmods.com

 

I've just had new 200 cell custom cats put in as my bank one cat had collapsed internally and had landed on the upstream lambda sensor effectively blocking the flow path as it was sitting at an angle, causing a P0420 code and the engine light to be illuminated. On my way to get the cats replaced I tried a full full throttle pulls and it almost felt like the dsc was operating in the way that it felt physically held back, on the way home with the new cats it felt like I had gained about 200HP.

Hopefully you can get it sorted, this thread had me worried that something else was going to go wrong with mine, it's been an expensive year so far...

 

So, I stuck a borescrope down cylinder #1...

Before we look at my pictures, have a look at Pavel's 2009 Jaguar XF Supercharged AJ34S engine rebuild » PRE Tuning - Site



This is what I was expecting. What I got was a little different;;;









Looks pretty bad to me. I wonder if that can of Upper engine cleaner didn't just transfer all the crap from the intake onto the piston tops...

 

Well it's going in for a Motorvac carbon clean tomorrow, the workshop is around the corner from a Jag dealership, and the bloke reckons he's had to do a lot of Jags. Especially the 5.0L which being direct injection gets choked up pretty bad?

Had a bit of a chat with him, he asked what the car was doing, asked had I changed the plugs recently, and after I explained all that i'd done, especially about the new cats going on next week, he didn't seem too surprised at all. "yeah they all choke up eventually"

He's also cool about pulling out the #1 plug and sticking the borescope down the cylinder afterwards. The service from him costs a bit more than the other guys quoted, but I have a lot more confidence in these guys just from how they were over the phone.

 

Break out the champagne gentlemen!!!!

 

so the carbon cleaning did it??

 

Well let me explain a bit more.

Had the carbon cleaning done on Friday. It's actually a two-stage process.

First the cleaning solution is drawn into the intake via a vacuum line, which cleans all the crap out of the throttle body, intake elbow, supercharger charge coolers and the intake ports/valves.

The manifold vacuum is measured and they watch for the change in vacuum as the crap gets cleaned out. Apparently it took three "rounds" of solution to get the vacuum back to the right level.

The second stage is introducing the cleaning solution to the fuel line, at the fuel pumps. They actually disconnected the line from the pumps, connected a tee piece and fed the solution in mixed with the fuel. This is to clean the combustion chambers and piston tops.

Apparently my car smoked out the whole workshop and the mechanics working on other cars had to stop work for a half hour, they had to open up all the doors of the workshop to clear the smoke out. That's "not normal" according to these guys.

They also told me that if my cats weren't clogged before, they certainly would be now. Also it's wise to do the cleaning before you put in new spark plugs. Great...

Anyway, the engine seemed to feel a bit better at low revs, but still pinging and hesitant in the top end. So it didn't actually fix the problem.

Today another workshop fitted new 100cell metal-substrate cats. And OH MY GOD what a difference.

First impression, at start up the exhaust was LOUD and crackled. At idle it was noticeably louder and raspy. A few little blips of the throttle and it revved up and dropped down much faster, kind of like a big-bore Japanese superbike, totally different to before.

Stabbing the throttle to 1/2 on the way from the workshop to the motorway was a shove in the back and saw the traction control light up while the tyres were cold.

While driving the exhaust was noticeably louder, a lot more drone, and more "european" sounding, you know that sort of metallic sound Ferraris make?

So I got onto the motorway, was holding it in 2nd at about 3500rpm, mashed the throttle into the carpet and it was a huge shove in the back, it launched forwards and hit the rev limiter at 6100rpm, in an instant. Pulled so hard and quick I wasn't expecting it and didn't shift in time.

I was shocked.

Gave it a couple of blasts on the motorway, pulled so strong to redline, seemed like it would never stop. The physical sensation of accelleration was incredible.

And no detonation. Just awesome power.

Unfortunately the workshop was so flat out we did not have time to put it on the dyno, but I will absolutely get a run in to see what the real difference is from the last pull 12 months ago.

So, long story short, with the wisdom of hindsight;

It was the cats choked up

It was not the coils
It was not the fuel pressure sensor
It was not the fuel filter

It probably needed new plugs anyhow because they were all fouled up, because of the cats being choked

It probably would have needed fuel pumps in the next 5 years or so, because they were falling off in the top, and a few of these have needed new pumps to keep up with the higher boost.

11 years old and 174'000kms / 108'000miles, time for a carbon clean and new cats.

 

Congratulations, Cam. Your persistence and thoroughness have provided an important education and fair warning for the rest of us. Enjoy your newfound power!

I guess the next question is, does anyone know of a source for equivalent 100 cell cats in the U.S.?

 

I don't think there is a huge difference between 100cell and 200cell, from a performance or an emissions perspective.

Nameless Performance has off-the-shelf 200cell cats that will bolt straight up to the factory exhaust and manifolds, but for sure they are not cheap.

I guess the lesson here is that cats do not last forever, they have a (limited) lifespan and if your car hits 100'000 miles, it's best to change them out.

I have been thinking about the 100'000 mile "barrier" since this is the major service for the V8 engines, when they get new spark plugs, and so on. If we say 10 years / 100'000 miles there are a lot of things that you should change out, which aren't in the service schedule, cats is definitely one of those things.