Solution for scenic II 1.9dci black smoke/ lack of power

This post begins with Renault scenic II 1.9dci problem that has lots of black smoke and a lack of power, then followed with senior technicians advising, finally the problem is fixed with the help of Renault Can Clip V152.

Car model and year: scenic II 1.9dci

Car problem and symbol: I’ve just bought a very cheap 55 plate scenic, the seller told me it needs a turbo. It drove home with no problem other than lots of black smoke and a lack of power… The smoke smells like the cars being very over fueled rather than burning oil. I’ve only had a very quick look at the car but diagnostics are showing nothing other than fuel temp at -40

The following parts are questions and answers between a senior technician and me:
Question: Forget the fuel sensor temp… typical false read on OBS2 readers.

If you are suspecting overfueling, air filter and EGR clean.
Both of which can reduce power and leave smoke trails although generally only really visible on hard throttle in following headlamps
Not done a turbo on one of these so can’t offer details.
How much black smoke ??
And when ?
Answer: quite a lot of smoke under anything but the very lightest of throttle, the car drove 50 miles at about 50/60 mph with no issues other than smoke and low power. I should go get my hands dirty rather than picking brains I guess lol
I’m not sure how much impact the fuel temp being seen as -40c would have on the fueling too ?

Question: Fuel temp isn’t being seen as anything. I’m not even sure there is a sensor.

The Renault diagnostic system conforms in the loosest possible way to OBD2 requirements.
Which cover main items and the plug dimensions IIRC.
But Renault go far further so there is a load of software gunk going up the port.
Generic readers mis-read these or try to make sense compared to their internal database… and fail.
Mine shows -52 IIRc and always has done. Ignore it, irrelevant.
Continuous smoke would suggest something more radical…. turbo oil leaks, valve stems, piston rings for example.
Turbo probably first port of call but you are doing the right thing questioning someone else’s diagnosis, could well be wrong.
As my old boss used to say, “give it a good coating of looking at…”

Answer: I’m on a dealer tool with v125 software (I’ve been told before not to use the word on here for some reason? As the smokes very black rather than grey or blue and smelly really like over fueling (think of a diesel being cranked for ages due to inop heater plugs then finally starting) I’m tending to think its not a major engine issue also it’s not using oil.
Anyway I’ll have to start investigating I guess.

Fair enough.
Start with the simple like filters and egr.
Turbo not spooling or gate not opening will give similar
On EGR, make sure inlet pipes/manifold where the valve fits are clean and not coked up.
Amazed me the amount of gunk that came out when I first did mine.

Fixed Finally! Experienced tips share bellow.
Fixed… Here’s what I found and a lesson to anyone who assumes all repairs will cost a fortune, to my benefit as I got a serious bargain!

First thing found was a very seriously dirty air filter (it could have been in a coal mine for the last ten years and been cleaner!) I replaced this and guess what.. Still the same

next as i had the car apart a bit I checked the turbo for play and found no play at all (happy days!)

At this point I pulled and cleaned the egr valve and what looks like a motorised throttle body, also checking all the pipework I found the outlet pipe from the inter cooler had blown off and the jubilee clip had broken, put it all back together with a new Renault Can clip (total pig to tighten up) and hey presto no smoke and loads of power only remaining issue was a check emissions message which upon clearing the stored codes has gone too.