Bad idle and stalling LS 400 - Dennis

[breaksr]

Okay I know it's a 1992 Lexus LS400 but I'm having some problems finding how to diagnose this problem. History: 330K miles (not bad) and it was running rather nice until the enging cleaning at the car wash did some damage to the way it idles. Washed the engine and drove the car to work and home and it ran fine. Filled up with gas and the idle started to surge to 1500 RPM. Puting it into gear causes it to surge and the idle drops but as soon as you stop and put into park the idle surges again. Put new gas in the car after that tankful and the idle is real low now and the car is constantly stalling unless I put my foot on the gas pedal. Tried to clean the throttle body and found that it caused things to get worse (cleaning on the car). I've read some forums that talk about cleaning the Idle Air Control but it's not that easy to get off the car. Any other suggestions? Does the vehicle need the Plenum cleaned like the Q? I guess with 330+K miles all the nasty carbon buildup has finally taken it's toll. Sort of like the Q but seems to be a softer ride on the highway.

[elwesso]

without knowing about how the sexus idle system works, id suspect a vacuum leak or a connection that got water in it.. Id unplug all the obvious connectors and see what that does.

[qship96]

Start looking at throttle position sensor.............

[breaksr]

Okay. I didn't do any adjustments (turn any screws or remove any critical bolts) but I figure water may have damaged some electrical part. I hear you can clean/rebuild the Idle Air Control on these cars. Must be more complicated then the one on the Q45.

[Q451990]

Didn't the older Lexus LS have distributors and spark plug wires? If so, I would pull the distributor cap and wires and look for water/corrosion.

Heath

[Q45tech]

Spark plug wires, Rotor caps [both] and both rotor buttons were last changed when? An every 60k exercise.

When was timing belt last replaced along with the $1,000 expenditure?

[breaksr]

I have to investigate but the timing belt was changed at 290K. I have to check on the other items (wires, distributor cap, etc.). Thanks Dennis.

[Q45tech]

The items are so problematic that we keep lots in stock.............also for some reason the driverside coils fail before the passengerside.............just replace both.

Finally in 1998 the went to coil on plug system, but then the drive by wire TB just became problematic and VVT................every car has its costs you can never escape.