Smoke from exhaust


Car Type:

1994 Toyota Landcruiser

After, and only after, I’ve been driving on the highway for at least 2 hours, I have a huge release of dark smoke coming out of my exhaust. This happens when I exit, and either slow or stop, then accelerate again. It’s huge and smelly.

Car repair shop can find nothing.

??? Emily


If the smoke is black then it’s running too rich. If it’s blue (which I doubt) then it’s burning oil.


black smoke is rich and I have the same issue with another vehicle. I recommend either driving faster if you can but obey the speed limit or shift down a gear @ your same speed. What is happening is that the engine is trying to get back into it’s sweet spot but the tranny is doging it down.


Black smoke is rich, specifically it’s full of carbon due to insufficient oxygen for the carbon atoms to bond to and create carbon monoxide and carbon dioxide.

Anyway, diagnosis will consist of testing (via checking their output signals) the various sensors that contribute to metering of the fuel, key ones being the upstream oxygen sensor, the mass airflow sensor, the manifold absolute pressure sensor, and the temp sensor.

The tech will also want to look at the exhaust gas recirculation system to ensure that it’s functioning properly, since it’s occuring only after highway running. The EGR valve allows a little inert exhaust gas to be mixed into the fuel when the engine is under load to displace some oxygen and keep the cylinders from getting too hot.

Personally, my money’s on a sticky EGR valve.


I chenged my mind. Since it’s happening after a highway run, perhaps the upstream oxygen sensor is malfunctioning when it gets heated up and sending a bad signal.

I’ll change my bet to the oxygen sensor.


A bad oxygen sensor, fuel injector(s) comes to mind. Or it might simply mean no pope has been elected.