1992 Lexus LS 400 missing

SEBURTON

MEMBER
1992 LEXUS LS 400
V8
2WD
AUTOMATIC
230,000 MILES

My 92 ls 400 has about 230000 miles on it and it develop a dead miss across the entire tach range under load or not very suddenly one day last week. I, doing the obvious first replace the plugs, wires, both caps, and rotor buttons, and it still has the same miss. I put a stethiscope on the injectors and sounds as if they are all working and I am at loss as to where to go from here. I live in a fairly rural area and no one works on these enough to have common knowledge of common problems. I was hoping you would have a suggestion as to where to look now.
Thanks

1 Reply

RASMATAZ

MECHANIC
75,992 POSTS

Check and test the following:

Oxygen sensor
Dirty fuel injectors (cleaning the injectors often fixes this).
Bad MAP (manifold absolute pressure) sensor
Bad TPS (throttle position) sensor
Bad or dirty MAF (mass airflow) sensor
Low fuel pressure (leaky fuel pressure regulator or weak fuel pump)
Vacuum leaks (intake manifold, vacuum hoses, throttle body, EGR valve)
Bad gasoline (fuel contaminated with water or too much alcohol)

Sometimes, what feels like a hesitation is actually ignition misfire rather than lean misfire. The causes of ignition misfire may include:

Dirty or worn spark plugs
Bad plug wires
Weak ignition coil
Wet plug wires