Questions and Answers

Lexus ESP 300 Miss, Sluggish, Vibrates Q. Vince, Thank you for receiving this letter, I have a 1992 Lexus ESP 300 with a 3.0 liter 24 valve V-6 engine. All power, automatic, ABS system, fuel injection, with 205,000 miles on it. I have recently had the plugs, plug wires, cap, rotor, and oxygen sensors changed. The fuel pump has proper pressure, the fuel filter has been changed, the pressure regulator has been checked, throttle sensor adjusted, and I run nothing below 89 octane in the engine.

The problem is the engine feels like it's missing, there is a definite lack of power unless the engine is cool and the temperature outside is 65° or less, it runs as if nothing is wrong. As the engine warms, the missing and lack of power returns.

If the temperature is 70° or above, the missing continues throughout the day. If I am traveling at 50 to 60 mph at a steady pace, there is a vibration while running down the road. You can feel the engine missing and it vibrating down the road. It has no problems starting, idling, or accelerating at higher speeds (at least that I can notice).

When running 50 to 60 and if accelerate, it seems to move smoothly. I have talked to many people about this, but I have no idea where to look next. Please help. Thank you in advance, Andy

A. I would suggest having the Coolant Temperature Sensor (CTS) checked with a scan tool, to see if it is reporting an accurate reading to the PCM. If the CTS is reporting the wrong temperature it will cause a drivability problem but not show up as a DTC since it is sending a signal, albeit a wrong one. The fact that the problems changes with temperature also makes me suspect the CTS.

There is also the possibility of a bad or clogged injector. An injector balance test will prove or disprove this and pinpoint which injector(s) is/are causing the problem.