View Full Version : Black smoke at low revs

07-04-2017, 08:11 PM
Hello everyone!
This weekend I followed my Jeep in another Jeep and noticed some black smoke when accelerating at low revs (under 2000 rpms), so today I changed the air filter and saw some improvement but there still is some smoke at low revs, especially if accelerating harder before the transmission downshifts. It seems like once the engine speed is above 2000 or the load is constant, the smoke clears up.
I've checked the turbo actuator and it's not sticking but I can't test if the actuator responds to vacuum as intended.
The intake manifold is probably gunked up by EGR and oil vapors, could that have any effect?
What about the MAF? Could a faulty MAF cause overfueling?
My EGR is electrically disabled, I can take if apart to check for leaks.

Fuel consumption on my recent 3000 mile trip was my best ever: 34.13MPG on one 400 mile stretch of high-way, 31.65 with some headwind and passing semis, similar 400 mile section and 33.17 coming back on the same section. The rest of the trip included driving in rural France and Germany and the usual traffic jams around Paris but the total average was 29 MPG

07-04-2017, 09:03 PM
AdrianD - Just curious what device you are tracking your trips MPG info with?

I have also had considerable amounts of black smoke come out of my exhaust on my 05 sprinter 2500 w 360K M. But only after being parked in one location for a couple of weeks and only starting the van periodically to let idle and charge the battery.. could be a clue?

07-04-2017, 09:17 PM
I'm using the full tank to full tank method. When the pump first clicks I stop pumping fuel. The average fuel consumption over 25.000 miles is under what users in Germany report for this exact car and the difference between the trip computer MPG is the same as reported by others. Average MPG reported by the trip computer was 32.66 vs 29 calculated.

Ah, one clue for my situation, after idling for prolonged periods in traffic jams, when I accelerated, the engine was a bit shaky and puffed more black smoke but it was back to normal after that one acceleration.

07-04-2017, 09:20 PM
Looking at the 2003 (OM612) powertrain diagnostics manual (from http://www.diysprinter.co.uk/reference/2003SprinterManuals.zip )
A sticking injector could cause black smoke (but i think it would do it at idle, too)

As you saw, a dirty air filter can affect it, too.
Certainly any number of the sensors (MAF, IAT, rail pressure, MAP) could contribute.


Oil from turbo lubrication can accumulate in the intercooler as well... and when airflow increases it can cause some of that oil to be carried along into the intake manifold.


07-04-2017, 09:42 PM
Looking at the 2003 (OM612) powertrain diagnostics manual (from http://www.diysprinter.co.uk/reference/2003SprinterManuals.zip )
A sticking injector could cause black smoke (but i think it would do it at idle, too)

As you saw, a dirty air filter can affect it, too.
Certainly any number of the sensors (MAF, IAT, rail pressure, MAP) could contribute.


After the Jeep trip during the weekend I expected the air filter to be shot. We drove on roads where visibility was under 50 feet because of dust. Changing the filter did clear up most of the smoke.

A worn injector would cause such problems, the previous owner installed 5 rebuilt injectors about 60.000 miles ago and I ended up sending two of them for a rebuild. I'm hoping it's not the case of worn injectors just yet...

Should I try to drive with the MAF disconnected?

07-04-2017, 09:49 PM
And yes, your EGR could be adding fuel-laden exhaust back into the intake stream
(after all, when you're accelerating the system does add extra fuel for a while)

You can certainly try it with the MAF disconnected, that's a very cheap/easy test.


07-05-2017, 12:42 AM
Take the cap off your disabled EGR. Verify the shaft is turned all the way to the right (to satify yourself that its off, turn it all the way to the left and the engine should die at idle. That's full on)

Found out the EGR can blow open under heavy boost and stick there, as it's no longer self cleaned when unplugged. Best to physically turn the shaft and the then stop it from turning with some sort of high heat epoxy

(These are the 2004- style EGR, not sure about the older ones)

Sent from my STV100-3 using Tapatalk

07-07-2017, 02:05 AM
Is your engine also surging? I chased the black smoke problem for a long time on my 2004. Turned out to be a crack in the innercooler. I have a tread on the symptoms, under my profile

07-07-2017, 08:28 AM
No surging, idles fine, minimal smoke once boost and rpm is up.
Today I will be driving behind the Jeep again, so I can check with the MAF disconnected.
I checked for VNT free actuator movement and disconnected the vacuum line, forgot it disconnected and then it smoked worse. I have a spare vacuum solenoid and test with that too. Maybe due to age, the actuator or solenoid are slower to react. People with VW TDI's of the same era always have problems with the actuators and solenoids.

Eric Experience
07-07-2017, 11:16 AM
One possibility is a vacuum leak stopping you from getting turbo control. Just get a vacuum gauge and measure the vacuum at the brake booster and compare it to the reading at the input to the turbo control solenoid. Eric

07-07-2017, 07:21 PM
Good call! I might just need to get a vacuum gauge and a vacuum pump. Yay more tools!

Weather today, no way I could see what's going on with the smoke output:

07-23-2017, 09:27 AM
Still no opportunity to test without MAF but yesterday I got some sensor readings while idling in traffic.

So basically the engine sees almost 1.2 psi of boost idling in gear, compared to the barometric pressure. That doesn't seem ok and I've had trouble before when the MAP sensor would show high readings at idle and cause LHM.

07-28-2017, 07:39 PM
Disconnected the MAF and drove behind the Jeep, minimal difference in smoke output.
When checking the values, I can see that the boost setpoint is lower than the measured boost (and equal to the barometric pressure). If I press hard on the MAP connector the actual boost reading goes down. Next thing to test is compare with an identical car.
Also I drove it accelerated hard on some straight pieces of road, there was some black smoke behind me when accelerating, nothing scary tough and the highest boost I saw was 23 psi gauge.
Tomorrow I will check all setpoints vs actual values.

07-28-2017, 11:36 PM
There are at least 2, possibly three pressure sensors in the intake system, the ambient, one after the air filter, and one after the intercooler somewhere. If all three of them are not very close with the engine off, you can have trouble. I believe the factory spec is 10 millibar max difference?

07-31-2017, 07:42 AM
First picture is idling in neutral, second is engine off and ignition on.

I will check with the intercooler hose disconnected next.