Black smoke from exhaust?

Hi,

The fuel trims are controlled by the powertrain control module (PCM) and other sensors. They couldn't have manually adjusted it.

A rich fuel mixture can be caused by a couple of things. For example, excessive fuel pressure due to a regulator issue, a failing fuel injector, or even an engine coolant temperature sensor. By any chance, do you have access to a live data scan tool? If you do, when the engine is cold, check the coolant temperature signal to confirm it is close to the ambient temperature.

Also, let me know what the short-term fuel trims are at idle and the engine at operating temperature.

Let me know if this is something you can do or have done.

Take care,

joe

Thanks Joe. I’ve taken my QX60 in 6 times for the same issue (black smoke from the exhaust). They’ve replaced the engine air filter, done an engine performance service and throttle body cleaning, and reprogrammed the ECM after the check engine light came on with a P0101 code for the MAF sensor. Today they told me the cause of the black smoke is excessive sludge buildup at the intake and exhaust valves. They likely won’t cover it under warranty because I only did oil changes every 6 months but drove 9000 miles between each oil change. The car has 47000 miles on it. Can an engine flush remove the excessive sludge? Or a mechanical clean? How much will this cost me? Thanks!

Hi,

If you do an engine flush, it won't reach the intake or where the valves are sludged. You know, neither of those things makes sense to me. Black smoke is a sign of too much fuel reaching the engine. Did they replace the MAF?

If they didn't, try cleaning it.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/mass-air-flow-service

Also, the manufacturer recommends changing the oil at 7,500-mile intervals. I would hope they wouldn't hold that against you.

Let me know.

Joe

They refuse to clean or test the MAF sensor. Their final solution is to walnut blast the carbon buildup off the valves and hope the black smoke goes away. They claim carbon buildup is the cause of the black smoke, but I think it’s the reverse. What do you think?

If there is a carbon issue, I would think it would cause the vehicle to react differently. Do me a favor. Disconnect the MAF and see if the smoke is gone.

Disconnecting it will force it into a predetermined setting to allow the engine to run. However, it shouldn't cause smoke.

Let me know.

Joe