Diesel engine decarb

**Karlos** · 11-02-2017, 12:20 PM

G'day guys,
Got a can of liquid moly decarb spray today and just wondered if anyone has used it before, what the results were (if any) and how best to get it into the intake? I'm guessing after the maf but not sure as the instructions are basic.

It's a 2011 CEGA 2.0cr TDI off a octavia Rs

Thanks in advance
Karl

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**Mysticality** · 11-02-2017, 12:55 PM

Don't put it in after the MAF, as it'll sit in the intercooler and become one huge lump of liquid ready to be ingested as soon as you hit boost.
I'd vote go in through the EGR valve, or take it somewhere like Camden GTI and get them to do it.
They've been heavily involved in a CEGA before.

**Umai Naa!!** · 11-02-2017, 01:15 PM

Much harder to do on a diesel. Need to get it in somewhere close to the intake flap.

I don't find it as effective on diesels as the petrol version is on petrol engines.

You'd get much better results physically removing the EGR and intake flap, and cleaning them by hand with brake cleaner and a few different types of stiff brush.

Bought a box of it 2 years ago, still have 3 of the 6 cans left. Just never need to use it.

**Transporter** · 11-02-2017, 06:29 PM

Originally Posted by Umai Naa!!

Much harder to do on a diesel. Need to get it in somewhere close to the intake flap.

I don't find it as effective on diesels as the petrol version is on petrol engines.

You'd get much better results physically removing the EGR and intake flap, and cleaning them by hand with brake cleaner and a few different types of stiff brush.

Bought a box of it 2 years ago, still have 3 of the 6 cans left. Just never need to use it.

BG diesel intake cleaning kit works quite well, if you do it often enough.

**Greg Roles** · 04-03-2017, 09:58 AM

The best way is to unbolt your EGR pipe at the intake flap, with the engine off, and pump that area full. Try and get the hose up in towards the manifold / four inlet ports. Bolt the EGR pipe back up and let it sit for a good while, and then try and start the car, which will take a bit of cranking. It will struggle and run rough till it clears. The next step is to spray it in with the engine running, I do it on idle and just stop as it labours, but I put it in PRE TURBO where the PCV inlet just before the turbo is in the air intake. The idea of a big pool in the intercooler is false, for sure you end up with some, but the whole idea is to get rid of buildup. Your intercooler ends up with a nice layer or engine oil from the turbo bearings anyway, don't kid yourself it stays nice and clean, better to try and flush it out a bit with these sorts of sprays. For sure they don't beat a physical clean, but who really bothers in the general public, as it's a super dirty job. These sprays sure beat doing nothing!

Put it in anywhere AFTER the MAF and you will get some effect, diesels are alot tougher than people think. The REAL issue is all this crap ends up in your DPF, whether cleaned out via spray or not, I think you should all worry more about that!

**Greg Roles** · 04-03-2017, 10:04 AM

Originally Posted by Umai Naa!!

Much harder to do on a diesel. Need to get it in somewhere close to the intake flap.

I don't find it as effective on diesels as the petrol version is on petrol engines.

You'd get much better results physically removing the EGR and intake flap, and cleaning them by hand with brake cleaner and a few different types of stiff brush.

Bought a box of it 2 years ago, still have 3 of the 6 cans left. Just never need to use it.

The diesel version can't be anywhere near as volatile / combustable for obvious reasons, I agree it's poor in comparison. Putting the petrol version through a diesel is possible, I do it from time to time, but you have to limit the airflow to avoid redlining it!

**Karlos** · 04-03-2017, 10:39 AM

Thanks for the replies guys! I thought about taking the manifold off and cleaning it with oven cleaner and a bit of elbow grease like I did on my BKD TDi but it was a prick of a job and it's a bit more complex on the CEGA! The instructions say hold the rpm at 2000 and empty contents of can but if the revs increase (I'm guessing the motor using the contents of the can as a fuel) then shut it off.

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**Ryeman** · 04-03-2017, 11:31 AM

Peugeot have a DPF cleaner separate from the DEF (AdBlue) as standard now
https://www.dieselnet.com/papers/9909rhodia/

as much as as I like diesels, you have to wonder whether the price is worth paying today
and
direct injection diesel and petrol engines also have intake valve fouling issues

**Transporter** · 04-03-2017, 02:59 PM

Even if you do nothing, the deposit in the intake won't affect the performance too much in the first 150,000km at least and the majority of the diesel engines don't block the intake to the extreme like you see in the picture on the internet. It's just another example of the hysteria in the media.

**Ryeman** · 04-03-2017, 03:09 PM

Originally Posted by Transporter

Even if you do nothing, the deposit in the intake won't affect the performance too much in the first 150,000km at least and the majority of the diesel engines don't block the intake to the extreme like you see in the picture on the internet. It's just another example of the hysteria in the media.

I'm of the old school that considers 150k as being fully run in.