Diesel engine decarb

[Umai Naa!!]

It doesn't break down the baked-on carbon around the EGR.

The oily residue, yes. The sludge, maybe.

[aSimpleLife]

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...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...

Was hoping I could get your opinion on what I might have done wrong trying this Liqui Moly Diesel Engine Decarb spray.
You have already helped me over on my T5 Transporter thread with my 103kw CAAC engine...thanks very much again.

Can I salvage anything from my T5 train wreck

To try and get rid of my EGR fault code, I am about to remove my EGR valve and give it a physical clean.
Before I did that, I wanted to give this spray a go, just in case it was enough.
However because I am still such a novice with T5s and diesel engines, I wasn't sure what was what from your description.
So before I worked that out, I followed the Supercheap video for this spray and sprayed a third of the can into the throttle body.

https://www.youtube.com/watch?v=3agltbN4C7M

Car was still running after this and I took it for a 20km highway run.
Then turned it off and on again a few times as I ran some further VCDS tests.
Right at the end I did a code reset with my final test.

Next day I've started the van and it ran for about 10 seconds, sputtered, then cut out.
Tried it another 5 times and it cuts out after 3 seconds each time as if it's starved for fuel.

Left it for a couple of days and have tried it again.
Same thing happened.

Unless it has returned to my previous immobiliser problem...which was similar...and seemed to fix itself after not being started for 2 years?I seem to have just caused a new problem using Liqui Moly?
Or by performing the codes reset after this?

And I am not sure yet what to try next?

(Also, your suggestion on my other thread to change the engine loom is still on my to do list. I was just trying to exhaust the other easier options first.)

[aSimpleLife]

I think I've answered my own question...but I thought I'd post my conclusion anyway.
I don't believe I've sprayed the Liqui Moly in the wrong area and caused my engine to cut out after 3 seconds every time.

I believe this latest problem is just a coincidence.
And that this is my apparent immobiliser problem resurfacing from 2 years ago.
I have no new error codes since spraying the Liqui Moly.
It ran for 20km on the highway afterwards. And I stopped and started it several times.
Why it chose now to trigger I don't know...but I'll deal with that back on my own thread.

Where I sprayed, the large hose I disconnected from the "throttle valve module" ("throttle body") must come from the air intake/turbo, making it downstream of these and also of the "Air Flow Meter" (MAF sensor).

I followed the afore linked Liqui Moly video on the Supercheap Auto site and these product instructions.
"This should be positioned downstream of the air flow meter/turbocharger/charge air cooler, where possible directly in front of the intake manifold."

It is still possible the Liqui Moly has coated or damaged a sensor but I am not sure which one or what to do about it?
Perhaps a "Throttle Position" sensor and/or an "anti shudder control" sensor?
But if that was the case, others should have reported this over time, and I can't find any real evidence.

It's been suggested I use a "throttle body cleaner" to remove any remaining Liqui Moly.
But which one for a diesel?
I am especially cautious now about spraying anything inside this engine that I don't understand well enough

There was some good information about this subject over on this thread too.