Yes you have my attention.

No it was only the electronic measurement via SDD.

Yes the sensor may be wrong, although that does seem less likely now given that changing to new pumps resolved the pressure dropping off. I have since been informed that the other X350 XJR that got new pumps was also doing the same thing. The audible difference between the old & new pumps is also indicative of "better" I am 99% sure there are no fueling problems with this car now (1% on clogged injectors)

But you can see forum attachments, here's one, the rest of the pics look the same except 330ms further along.



I am hoping to sort this out on the weekend.

Exactly what I was thinking.

I doubt that, the car is making less power than it did 12 months ago (or > 2 years ago) with the same pulley & intake, there were no apparent issues back then. Other engines with more extensive mods have not reached that limit. And they made good power, mine doesn't at the moment...

I cleaned the MAF & it made no apparent difference. I do suspect that it might be failing somehow.

The injectors from the 4.2 have enough flow for >500hp at stock pressure, the only way they could be maxed out is if they were blocked up, which is one reason why I was thinking of the carbon cleaning. Avos was running the stock 4.2 injectors at ~600hp

I doubt that it would be possible to max out a properly functioning stock MAF with the limited mods on this car. There are other exact same engines with exact same MAF that are much more modified (top+bottom pulley, cats, etc) and they never maxed out the stock MAF. Again, it was fine 12 months ago with the same setup, so something has gone wrong.

I will look into the pinpoints.

The flap was removed a long time ago.

I confirmed flow through the intercooler circuit (at idle) but have not specifically monitored the temperatures as the readout in SDD is only in volts and we don't actually know what 0-5V is in ºC for the IAT2 sensor...

Have not been specifically monitoring. BUT in the past I did have overheat issues (stuck thermostat) and there was no pinging then, even at well over 110ºC

All tight & seated properly as far as I can tell. I took the intake tube off last in September, have not had issues since, prior to the issues.

Will have a read later. Thanks Plums.

Just to throw another one out there, it's been suggested that a failing Coil-On-Plug could cause this...without codes for misfires or coil-related problems it'd be a case of replacing a bank or the lot. Any ideas on how to isolate a bad COP without knowing which one is bad (or there might even be multiple)

WOT flap removed from airbox, K&N filter, SS intake tube in place of the stock plastic one with bellows, chambers, restrictions, etc. Same as it's been for the last couple of years. No changes.

 

Did you get around to removing all spark plugs for comparison?

 

Maybe JEPC etc show part # for IAT2 in case it's the same as IAT or ECT - whose transfer curves we know. Oh - some/all are .... where have I seen them .... Tech Guides?

I do tend to think MAF is #1 suspect.

Odd things happen with blocked cats but not what you're seeing AFAIK.

 

The problem with the images not showing may be that they are
not publicly visible to someone without the user credentials. They
would be visiible to you since you have the credentials cached on
your own machine.

Turning to the one image I can see ...

I would log the following:

rpm
air mass
throttle position
absolute manifold pressure
ignition timing
fuel injector duty cycle
closed loop status

Having those datum in a synchronised timeline would be useful
in seeing any anomalies in the ECM view of the world as well
as identifying where you are at particular points of the test.

 

Just regarding the pictures Plums, I am not logged into Dropbox on my work laptop and the pictures are visible. The pictures are public and they should be visible to everyone. Unless you have some extra-strong adblock or security program, or an old browser...

 

It's a certificate validation problem with the dropbox ssl certificate.

They have failed to install the intermediate cert that completes the certificate
validation chain.

I can view them if I open each one in a separate window and tell IE to ignore
the cert problem.

 

Ah OK then.

Well I just went nuts & ordered 8x Airtex coils, 8x Denso plugs, 2x Denso O2 sensors and an Spectra MAF

Rock Auto has a good selection, $930 delivered that's $650 cheaper all up than buying from the UK (Aussie dollars).

How do I justify this?

- The plugs in the car don't look all that great anyhow...
- The MAF is the original unit at 11 years old & 174'000kms
- The coils are original at 11 years old & 174'000kms
- The O2 sensors are original at 11 years old & 174'000kms

Will know more in a week or two...

 

That's your story ... better stick to it when you get home

 

Just ordered a new fuel pressure sensor as well, for $85 delivered it's crazy not to change it...

Because a little bird told me that it can happen that the pressure sensors start to fail, and they read high, to which the ECU reduces fuel flow, which leads to a lean-out...

So i'm told...

 

If it is true, it would be sensible.

The ECU would reduce fuel injector duty cycle to compensate for higher than expected fuel pressure.

The other way to compensate would be to reduce duty cycle at the pump, but that would be
a coarser and slower adjustment.

The two mechanisms are probably used in concert.

Your reported 70 psi does sound a tad high. A mechanical fuel pressure gauge would have proven it
one way or the other.

I think you just like shopping

 

Not really, but i'm at the stage where I will either throw money at it, or petrol and a naked flame...

 

It is possible, given a sufficient quantity of AN fittings, to put a mechanical gauge in line.

What the EPA has against Schrader valves I could not tell you.

 

Plugs, coils and O2 sensors arrived today, pulled the old plugs;







Oops I forgot to take a pic of one of them...it was also sooty, not much brown unlike #1 & #8

The 3rd pic is #1 which is the same plug as previous pics, you can see the difference in colour and deposits compared to before. I guess that's the detonation at work...

4th pic is #6 (left) #8 (right) surprises me to see such a difference in the cylinders.

Haven't been out for a drive with the new plugs/coils, waiting on the fuel pressure sensor to arrive since it'll be easier to install with the scuttle & cabin filter removed.

Depending on work I might put in the new O2 sensors this week.

The MAF that I bought is a dud. Aftermarket item from Spectra Premium via Rock Auto. I didn't even take it out of the bag, somehow the design is completely different, there is no hole in the sensor body for air to pass through. Very strange, so i've sent that back.

In the meantime Avos pointed out that the MAF signal appears fairly normal based on an old dyno sheet of this car, between ~5000-5800rpm the engine only makes 30rhwp more, and the MAF measurement was an increase of about 30g/s over that range, which correlates about right.

So, waiting, waiting, waiting for my fuel pressure sensor...

 

Detonation of the magnitude you're mentioning does not result in plugs that look like this nor does it appear that the engine is running lean. If anything it's way rich.

Are you sure there's detonation?

 

Yep. For me the plugs looks like the AFR is pretty rich, no evidences of the detonation can be visible on the plugs.

For me it looks like there's no detionation, but it is possible that there's pre-ignition of the mixture from a carbon deposits in the cylinder(s).

If it was a one of my customers cars - i'd take a good look into the cylinders with a scope.

 

As far as I understood the misfires (that is how I read it for now) occurred at wot and high rpm, so the plugs have only been very briefly exposed to that condition.

The mixture should be measured at wot to know if it is good or bad, and ideally also an external gas analyser test (in neutral about 2500 rpm) so you know that the ECU is able to keep lambda perfect. With that you will have ruled out already many potential issues that can cause misfires.

Next would be the cops, malfunctioning ones can show their ugly head only under boost causing misfires.

If that all shows to be fine, and the condition stays bad at wots, it may also be clogged catalysts.

 

As i read this i've imagined a cops, chasing a Cambo351 while he's trying to measure an AFR@WOT on a highway

 

I agree that it is generally rich, always has been. Which is one of the reasons why i'm changing out the upstream O2 sensors.

What surprised me was the colour change and clumpy deposits on plug #1 compared to a few weeks ago.

The car has only done less than 30km since this all started, and most of those have been on the motorway with some WOT runs. So the colour change kind of makes sense. But the variation in colour between the cylinders is what has me wondering...

I've had a couple of cars in the past that pinged, so i'm pretty sure I know the sound. But it could also be pre-ignition like MoscowLeaper says.

I have a cheap digital borescope, but this will only allow me to look at the top of the piston, not at the combustion chamber or the valve faces. I should have stuck it down there when I had the plugs out...

I looked into the carbon-cleaning, there is no-one local to me with the equipment that I could find. The DIY options are Seafoam or the Subaru Upper Engine Cleaner but some people have said that using this on a high-mileage engine that has not been cleaned before could choke up the catalysts because of so much crap being released from the cylinders.

New coils and plugs are in the engine now. I checked the gaps of the new plugs all at around 0.040 to 0.044 (my cheap gauge is not that accurate)

New O2 sensors to (hopefully) reduce the richness.

New fuel pressure sensor will go in to rule that issue out. Looks like it has not been shipped from the UK yet so I will probably have to buy one local at twice the price...

Regarding the catalysts, they are the originals so 108k miles on them, were on my list of things to do, are now at the top of the list.

Once the O2 sensors and FPS have been changed then I will make some more road tests, and head to the dyno to do runs with the wideband in the tailpipe, and more logging with the SDD. Hopefully those runs will be with a good running engine, but we'll find out sooner or later.

 

LOL it nearly happened, I caught up to a police car during one of the road tests, and went past one on the side of the road another time....

 

OK so I put in the new O2 sensors, and couldn't help myself, had to go for a drive.

So this is with new plugs, coils and O2 sensors. Still waiting on the fuel pressure sensor to arrive, probably another week...

The scuttle removed, no wipers, no cabin filter.



So it sounds awesome inside the cabin, except for the pinging...

Here's a recording, it's an .m4a file off an iphone, but I had to zip it in order to upload to the forum.

New Recording 2.zip