Engine misfire and rough idling?

WISDOMNAIRA

MEMBER
2007 LEXUS IS 250
2.5L
V6
4WD
AUTOMATIC
165,000 MILES

Just purchased the vehicle listed above and performed oil maintenance with semi-synthetic Mobil super. After driving for a long time, I notice the engine begin to stutter in motion and the exhaust emits black smoke. What could be wrong?

Friday, May 24th, 2024 AT 5:25 AM

1 Reply

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

This sounds like a stuck or shorted fuel injector, to find out which one it is let's remove the spark plugs and look for the one that is black with soot, this will be the cylinder that is having the issue. Here is a generic guide to help you step by step with instructions in the diagrams below to show you how on your car.

https://www.2carpros.com/articles/how-to-change-spark-plugs

and please go over this guide as well which will show you the causes for the black smoke.

https://www.2carpros.com/articles/engine-black-smoke

MAKE
DENSO .................... FK20HBR11

GAP
Maximum gap for used plugs .................... 1.3 mm (0.051 in.)
Correct gap for new plugs .................... 1.0 to 1.1 mm (0.039 to 0.043 in.)

TORQUE .................... 25 N.m (254 kgf.cm, 18 ft.Ibf)

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