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About 2 weeks ago my r53 started to feel really sluggish at WOT. I checked the codes and I have a P0108 for high pressure in the intake manifold and a P0420 code for the catalytic converter. The previous owner had the catalytic converter replaced by the dealership when I bought the car at 110k, so I don't think that it's the issue. I currently have 117k miles on it. I also have noticed that my oil has a strong smell of fuel and I am only getting around 17 mpg. I don't have any dash lights on.

I tested my fuel injectors to make sure they were opening, replaced my coil pack, plug wires, replaced my spark plugs about 3000 miles ago, and I did a timing chain replacement 2000 miles ago. Yesterday I wanted to check the supercharger BPV so I pulled that out and it was working just fine. All vacuum lines were in the right places as well.

I did a compression test as well, cylinder 1 was at 130 psi, cylinder 2 at 140 psi, both cylinder 3 and 4 were at 150 psi which is healthy. I am concerned about cylinder 1 and 2 having cracked rings because of the low compression and fuel smell in the oil.

What else can I check to diagnose the problem? Could the loss of power possibly be a bad fuel pump? I'm just not sure why I smell fuel in the oil.
 

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Youre compression test is good enough.
Follow the codes is my advise. I wouldnt care when the cat was replaced, its still an issue so go again.
 

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high pressure code could just be pulley size related, so as above I'd be pulling the manifold to just check the cat or pre cat which typically can block, using a borescope, if it has blocked or melted then address the running issue you have that caused it, most likely a pulley drop with no map or air leak perhaps, also I'd use said borescope to actually look into the cylinders and check for any marks etc. Did you find the plugs still tight when you removed them? Would contribute to air leak potentially.
 
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high pressure code could just be pulley size related, so as above I'd be pulling the manifold to just check the cat or pre cat which typically can block, using a borescope, if it has blocked or melted then address the running issue you have that caused it, most likely a pulley drop with no map or air leak perhaps, also I'd use said borescope to actually look into the cylinders and check for any marks etc. Did you find the plugs still tight when you removed them? Would contribute to air leak potentially.
I will check out the cat to see if it is blocked or melted and look into the cylinders.

The plugs were tight when I removed them, I have attached a picture of a spark plug, because they all looked the same. It looks like a concerning amount of carbon had built up around the base for only 3000 miles. What do you think?

I have been running this pulley as long as the spark plugs and I haven't had any power issue until now. When I replaced the pulley I got colder spark plugs, NGK BR8EIX.

100608
 

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Discussion Starter #6 (Edited)
Thats not a healthy plug.
That carbon would be because it's running rich?

I had ordered a scorpion header with decat pipe a few weeks ago and it should be here by the end of the month. I was going to have a shop weld my current cat to some flanges so I could swap between cat and de-cat. So if my cat is bad I'll just order the hi-flow one from scorpion.
 

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Does it smoke when its running? (out the exhaust)
So, to me that looks like it could be fouled by oil. Is that what you were thinking?

No smoke from the exhaust and idles perfectly around 750 with a +-10-15 rpm variance.
 

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2006 R53 Hyper Blue/White Cooper S
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Does honestly sound like a vacuum related issue TBH. Although the lines might appear OK, you might have a leak/split in one of the lines somewhere. Also if your PCV valve is broken that can lead to poor running, increase in oil leaks/consumption and poor MPG also.

I wouldn't be surprised if the vac pipe to the TMAP sensor isnt connected properly or is leaking...quite a common thing to go particularly if they've ever been interfered with at any point. Have a similar problem with my own car and having this investigated along with a replacement PCV valve.
 

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Quick one on PCV's My experience with blockages is noticeably high oil consumption, since a blockage increases crankcase blow back. I found it possible to clear the PCV by spraying a load of Isopropyl alcohol (us mountain bikers always have a bottle of that around the place 😉) or any common solvent & a year on, the PCV is still working fine. I think over time, the oil vapours condense in the valve to create a solid lump of oil sludge.
 

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Quick one on PCV's My experience with blockages is noticeably high oil consumption, since a blockage increases crankcase blow back. I found it possible to clear the PCV by spraying a load of Isopropyl alcohol (us mountain bikers always have a bottle of that around the place 😉) or any common solvent & a year on, the PCV is still working fine. I think over time, the oil vapours condense in the valve to create a solid lump of oil sludge.
Top idea this!

Is just a simple thing, if you remove it and it doesnt shake (theres basically a little BB in it which opens and closes the valve under vacuum) its gummed up. Is a cheap part anyways so doesnt hurt to change it out but for sure no reason it cant be cleaned as mentioned 👍

Another way of testing is to open the oil cap briefly whilst the cars idling and place a plastic/nitrile glove over the oil filler hole....if the glove inflates your PCV is blocked, if it gets deflated (I.e. air is being pulled out of the glove) all is well. Just be careful not to have the glove pulled into the rocker cover 😂 😂
 

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Quick one on PCV's My experience with blockages is noticeably high oil consumption, since a blockage increases crankcase blow back. I found it possible to clear the PCV by spraying a load of Isopropyl alcohol (us mountain bikers always have a bottle of that around the place 😉) or any common solvent & a year on, the PCV is still working fine. I think over time, the oil vapours condense in the valve to create a solid lump of oil sludge.
Great ideas! I will check all of these when I get home. The TMAP sensor is on the thermostat housing, correct?

I hadn't even considered the PCV since I had checked the crank case pressure with the glove trick a few month ago. I definitely have IPA lying around, I'm a mountain biker as well haha
 

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No worries, sounds like PCV is probably fine in that case if the glove trick was OK (y)

TMAP is the throttle body MAP sensor on the intake pipework near the throttle body. It has a vacuum pipe underneath which is quite easily split/broken if ever messed with and definitely worth checking.
 
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