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So, I've owned my GT for about 2 months now, and I love it! Technology is sublime with added mechless stereo, parking sensors & integrated dash cam. She's running an autodelta tuning box and all appeared OK until recently.

There was hesitation through all the gears up to about 2500-3000rpm. Now, I encountered this on my impreza a couple of years ago and it turned out I'd killed the MAF sensor...to the tune of £330 :(

My symptoms pointed at the following potenials...

MAP sensor failed
EGR failure
MAF sensor failed
Turbo actuator hoses split
Turbo actuator failed
Top/bottom hoses split

Turns out this was the problem...



...and this was half way through cleaning!!

My EGR is partially blanked at the moment, but once I have my carbon engine clean, it will be fully blanked, along with a new MAP sensor and a stage 1 remap with EGR delete.

Anyone else encountered a failed MAP sensor before?
 

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Yep, very common to pull out the map sensor and find it resembling a lump of coal.

EGR + crank-case vapour = thick carbon buildup!

Get the EGR mapped out and blanked off fully, then hope and pray your swirl flaps are in better nick than the MAP sensor was!
 

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Yup mine looked pretty much the same! Gave it a good clean and made a big difference.

My EGR is partially blanked too and once i get the delete done the inlet manifold is going to get a good clean and the egr bits will be coming off and a new MAP sensor fitted...
 

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When the MAP sensors are this clogged up, its likely the rest of the inlet manifold is similarly clogged. The openings to the inlet runners particularly on the 16v & 20v engines (where there are two small runners instead of one big one) will be significantly restricted. A 2mm deep coating of the black death on the inside of a 1 inch diameter runner means a whole third of its volume is lost. That has a big impact on the engine's volumetric efficiency.
 

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Discussion Starter #6
Yep, very common to pull out the map sensor and find it resembling a lump of coal.

EGR + crank-case vapour = thick carbon buildup!

Get the EGR mapped out and blanked off fully, then hope and pray your swirl flaps are in better nick than the MAP sensor was!
Done this morning :) feels like a new car now!
 

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When the MAP sensors are this clogged up, its likely the rest of the inlet manifold is similarly clogged. The openings to the inlet runners particularly on the 16v & 20v engines (where there are two small runners instead of one big one) will be significantly restricted. A 2mm deep coating of the black death on the inside of a 1 inch diameter runner means a whole third of its volume is lost. That has a big impact on the engine's volumetric efficiency.
As Pud says, if your map looks like that, then you manifold probably looks like this.
DSC_0042.jpg

This was off a 156 with 110k on the clock that I bought as it is a flapless manifold.

Took me a day to clean out, and also makes me wonder if that stuff in a Terraclean actually works and removes some of that crud, would I want that all wafting into my engine.
 

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Allow 2-3 hrs if you've not done it before. You don't need to disturb the cambelt as the HP fuel pump pulley can be bolted to the support bracket (it has 2 holes, just for that) thereby keeping the belt in place whilst you remove the pump. Wrangling the vacuum oil separator off the back of the engine is probably the most awkward bit, but it's not too bad once you understand where the 3 mounting bolts are.
 

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As Pud says, if your map looks like that, then you manifold probably looks like this.
View attachment 639482

This was off a 156 with 110k on the clock that I bought as it is a flapless manifold.

Took me a day to clean out, and also makes me wonder if that stuff in a Terraclean actually works and removes some of that crud, would I want that all wafting into my engine.
Terraclean is a fuel system cleaner only isn't it?

Even my Karcher at point blank range doesn't remove all that stuff, just the loosest bits. I usually have to do scrape it with a screwdriver. I really need to find something that will dissolve it. TFR doesn't touch it.
 

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Petrol, acetone or (less good) brake cleaner, I think, from dealing with what was left after oven cleaner. I used the oven cleaner that comes with a big plastic bag and left it overnight. A big gotcha, however, is that it plated out the carbon onto the manifold alloy, leaving it a sort of matt-brownish-black, so I then had to paint it with VHT silver.

I have a 25L jerry can of petrol contaminated with diesel that my son left here, from a customer's mis-fuelling incident. It's useless for fuel and with hindsight I should have just used that to clean the manifold. Outdoors :)
 

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I'll try one of those oven cleaner bag things. I've tried an overnight soak in brake cleaner before, it took some off but not the worst of it.
 

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I have a 25L jerry can of petrol contaminated with diesel that my son left here, from a customer's mis-fuelling incident. It's useless for fuel and with hindsight I should have just used that to clean the manifold. Outdoors :)
Nah it aint useless for fuel - you can stick it in your tank with no probs, whether you use it all in one tank or add 5 or so litres per full tank would depend on how much diesel there is in it, but its still perfectly usable. :)
 

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We don't know. It came out of a misfuelled diesel Mercedes, the owner had no real idea how full the car had been before she filled up. Probably around 20% diesel, 80% petrol. I did use some, heavily diluted about 1 gal in 5 gal of petrol, in my old petrol Renault, that was OK. But that car is now long gone.
 

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I'll try one of those oven cleaner bag things. I've tried an overnight soak in brake cleaner before, it took some off but not the worst of it.
Overnight it didn't take quite all of it off, there was still some in parts of the plastic plenum, but it did make a mess of the alloy.

Far the best solvent I've ever had was a 5L can of acetone I was once given. That had an amazing ability to dissolve anything, and I went on reusing it for ages as it seemed to be able to absorb several times its own volume of oily filth, and still dry off in seconds. But I think that might dissolve the plastic plenum too, given long enough.
 

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We don't know. It came out of a misfuelled diesel Mercedes, the owner had no real idea how full the car had been before she filled up. Probably around 20% diesel, 80% petrol. I did use some, heavily diluted about 1 gal in 5 gal of petrol, in my old petrol Renault, that was OK. But that car is now long gone.
Really ? I d be quite worried about putting any diesel in a petrol cars tank, but have no worries at all the other way round.
 

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Steam cleaner, perhaps.
I'd like one, I was spoiled with all the equipment I had access to when I was down in Bedfordshire. Aqua-blaster was a great tool for cleaning up alloy too.
 

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I believe that although diesels will happily run on petrol the ethanol destroys HP fuel pump seals and the lack of diesel lubricity trashes the pump and injectors. Some diesel in a petrol car normally does little harm, it's not that different from 2-stroke mix. However, more than a little and it won't run at all, I think it'll just douse the spark.
 
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