20 Most Recent 1991 Lexus LS 400 - Page 4 Questions & Answers

Most all pressure regulators are located on the fuel rail under the hood. It should have a vacuum line attached to it

Try this site: www.lexls.com

Most likely if its anything like the old lincolns the airbag/shocks are blown. If this is the original set on this vehicle very good possibility. Best fix is a replacement set or if the coil over option is available much sturdier.

Dirty injectors...try adding 2 bottles of Lucas Oil Gas Treatment...drive a day or so and feel the difference...also old dirty gas...has your Lexus sat for awhile?

There are 2 fuse boxes on the Lexus. The first is the main power distribution box and is located right beside the battery under the hood. The second panel is located behind the plastic kick panel under the dash on the driver's side where your feet go. The panel is vertical and covers the area from the dash to the carpet on the floor, just forward of the door. I can't remember if it's a pull off or if there is plastic twist nuts holding it, so check carefully before pulling on it.

Disconnect the seat heater and use a meter to check if there's any continuity on the heater or if it's an open circuit. If open, then heater is bad.

display dtc codes

MAP sensors are not cleanable, MAF sensors are.

Nothing to clean. It either works or not. Make sure the vacuum hose to it isn't cracked or loose fitting.

Or maybe too much fuel-backfiring in the exhaust is the burning of the unburnt fuel in the exhaust. Check the fuel pressure. You can rent fuel pressure gauges at autozone, I believe. If too low, possibly a bad filter or bad pump. If too high, test the fuel pressure regulator. a failed regulator can let extra gas into the engine through the vacuum line on it. Take off the vacuum line to the regulator, and watch the regulator for a minute with the engine running. If gas starts oozing out of the vacuum port at the pressure regulator, the regulator has failed and must be replaced. If pressure is correct, at least you have eliminated that as a problem. Check the air filter, check spark plugs and plug gaps, more or less back to basic tune up.

Check to make sure that none of the wire harnesses are touching the exhaust manifold and that the fuses and bulbs are tight in their fixtures.

You may be able to clear debris out by using a long thin rod and pushing it into the openings on the front of the sunroof drain channels the pouring some water in to make sure it drains properly sometimes the drain pipes become disconnected inside the headliner but try clearing the obstruction first and see what happens.

Check your MAF and MAP sensor. The first 80% of your throttle signal from the TPS works with the O2 sensor to try to keep the air fuel ratio to 14.7 to 1 with the ECM controlling the fuel injector spray time and timing the ignition. After the 80% to WOT the ECM puts the O2 sensor in to an open loop and takes the Reading form the MAF and MAP sensor to run the engine richer so there will not be any Detonation to the engine and burning holes in the valves for running too lean. That is why it always feel like you get a little more when you ease off on the gas peddle from WOT. Recap check the TPS, MAF,and MAP sensor and wires to those sensors, if you can get the car scanned that would be great and you may find out which sensor may have gone bad, the other thing to is the fuel pressure regulator may be going bad and at WOT the pressure may be to high causing it to run to rich causing the loss of power. Good luck and hope this helps. 

This might be air intake temp sensor or vapor lock.