Black smoke issue on my 3L km done Innova & how I solved it

I have raised this concern with the ASC and they say its normal for an old car which i don't agree.

BHPian admmys recently shared this with other enthusiasts:

Hello All,

I have been a voracious reader of the posts on the forum from various other BHPians but have never posted stuff myself. However, i'm faced with a peculiar issue with my vehicle and wanted some opinion on what could be wrong with my vehicle

This vehicle - Toyota Innova 2.5 VX has been a great daily driver, still is a great one with its driving feel and has been driven mostly within the family (not drivers) and taken very good care of with ASC services except for some body work that was done at FNG. Its in pristine condition mechanically other than the issue below.

We have the vehicle driven for over 3.1L KMs without any major issue (had regular replacements and wear and tear along with replacements of steering mount, AC Compressor and Driver Airbag sensor that was malfunctioning).

I replaced the brake pads, timing belt at 3L km along with the regular service of changing the filters (Air and Diesel). However off late I'm noticing for the last 5-6K KMs, there has been

1. Lot of black smoke like unburnt fuel that you see from your rear view mirror (soot like and not white/ grey)
2. Drop in mileage (8-9 KMPL vs 13 that i used to get earlier)

I have raised this concern with the ASC and they say its normal for an old car which i dont agree.

Some of things that i have done so far:

1. Get the injectors cleaned
2. Filters cleaned again (yes the new ones too)
3. Engine decarbonization
4. Used purge as well from liqui moly (which kind of made the drive smoother)

Here are my observations:

1. The smoke appears in the rear view mirror when i accelarate and cross 2000 RPM. (not a very scientific way but just my observations on my way to office)
2. The smoke doesnt appear when the vehicle is in the nuetral or if the clutch is fully engaged.

This leads me to think this has something to do with my clutch plate? maybe its jumping and worn out? The ASC says that should not be the case. The gear shifts are smooth however i'm not convinced from their answers.

Has anyone experienced similar problems and do you know what the solution could be? I'm planning to keep the vehicle as long as I can (until Diesel is banned) and will continue to use it for 20KMs trips every day across the city.

Thanks in advance

Here's what BHPian NomadSK had to say on the matter:

Black smoke from the old diesel engine mostly points to rich mix fuel input in the combustion chamber during hard acceleration. So basically more fuel is getting injected in the engine as compared to the fuel/air mixture. Hence partial combustion and low mileage.

• Get your injectors checked,
• since you have replaced the air filter that’s fine
• clean the EGR valve
• clean the MAF sensor
• Check the function of catalytic converter

Ask your mechanic to plug in OBD scanner, mostly the faults would get reflected in that.

Here's what BHPian Jeroen had to say on the matter:

It is definitely nothing to do with your clutch.

Somehow the air fuel ratio is incorrect, leading to a rich mixture and not burning fully. Hence the black smoke.

Apart from what you had done already, I would check the EGR valve and the air mass meter too.

How did they clean the injectors? I am not a great fan of injector cleaning. I would pull the injector and check them them for correct working on a test rig. Only way to make sure they are working properly.

As Jeeva pointed out, what about the timing belt? Did these problems start directly after the replacement of the belt? Usually, when a belt is placed incorrectly there are some ticking noises to be heard as well.

But that would be a last resort. I would check EGR valve for dirt build up and proper working , clean the MAF (make sure they use the correct cleaning agent and not just brake cleaner), test the injectors and take it from there.

Here's what BHPian cooldip had to say on the matter:

I have 1KD Fortuner with 169K on the Odo. Since the engine is very similar to the 2KD I'll share an experience.

I had very black smoke from the tailpipe on cold start. The problem had started after cleaning the injectors.

TASS wasn't able to diagnose the problem. All other parameters like EGR, filters, sensors and intercooler are always in ship shape.

I finally traced the problem down to injector seats. The injector seats are known to wear out and your's is well past its serviceable age. My TASS had taken the injectors out but never replaced the seats. As per the service manual the seats have to be replaced anytime the injectors are removed. Engine oil was entering the combustion chamber because of a pinched injector seat.

My suggestions

• Please get a set of new injectors (or Denso refurbished injectors) - this is expensive
• Please ensure that the TASS replaces all service parts as per the service manual
• Replace the vacuum filter (small white filter near the EGR)

BHPian admmys had the following update to share:

Thank you for all the valuable inputs. I was travelling for a few weeks and could not get back faster.

I paid a visit to the TASS and my mechanic who takes care of the car for years told me not to leave it in the showroom as the TASS is not really interested in getting to the root of the problem and will start opening up the entire piece by piece and get me a huge bill. He told me a bill of 2.8 Lakhs was provided to another 2005 innova user with similar issue and and he resonated the steps that were mentioned by svsantosh here as his suspected issues.

I then decided to turn to my FNG who maintains our 2003 Fiat Palio 1.2 NV.

I had the turbo checked and MAF sensor tested and they were all fine with soot however around them and was cleaned. There was no issue or error code that popped up either on the screen.

Hoses all appeared fine as well and no oil leaks either.

Based on svsantosh's comprehensive checklist, here are my inline comments:

1) Change all 4 injectors, they are past their prime. - They were inspected and i got the history from my dad who said they were changed at 2.1 Lakhs KMS when I was outside the country for a couple years and injectors were good to go.

2) Change fuel filter, air filter. - these were done at 3.03 Lakh KMS.

3) Remove and inspect and clear MAP, MAF. Mostly the MAP is covered in soot, post a pic here. Inspect Camshaft censor while at it, clean all sensors with isopropyl, google for it. - MAP and MAF had soot and were cleaned as well. My mechanic forgot to take pics before cleaning.

4) Remove intercooler and tie one end with a plastic cover and many rubber bands, and make it erect and fill diesel from top, soak for 1-2 hours, drain, fill with petrol, sock, drain, wash with tap pressure water, dry and refit. - He performed this action as well.

5) Remove Inlet manifold - inspect & decarbon it and spray the inlet with abundant WD40 or brake cleaner and de-gunk the valves. - This is where the culprit was actually. There was a lot of gunk that was choking the inlet. Have some videos that i will upload later.

6) Remove cat-con - wash from the 'wrong' way, exit side, with ton of water. Do it until water comes out nearly clean. While at it, clean the entire exhaust. - This step was skipped for now. Will be done along with step 8 in next month or so.

7) Remove EGR, blank... err, clean it and refit. - EGR was dirty as hell and was cleaned and fit again.

8) Please flush the engine with a proper engine flush and then drive it with a cheap oil again for 5-10 kms, and then again fill it with a good grade oil. 3Lacs is enough to have a ton of debris inside the mating surfaces and can stress the combustion cycle. - We didn't do this step yet as we wanted to see if the above addressed the issue to a certain extent first and it has reduced the smoke issue significantly. We will be planning to a complete engine flush next month. There was a ton of debris here that was cleaned up but a complete flush is to be done.

One of the points that my FNG mechanic mentioned was the ASS generally dont a complete flush and he recommended that whenever there is change in timing belt, as a thumb rule, tires, brakepads, discs, injector clean, EGR check and complete engine flush/ decarbonization should be done to increase the longetivity.

He mentioned he as a taxi driver whose 2009 Innova has run beyond 10L Kms and still going strong and he does the above activities with the FNG every 1L KMS no matter what.

Thank you all for the help and i will post a few videos of the gunk on youtube and share the link later this week.

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