Idle/stalling Problem

[zlilz]

Hey, I have an 91 LS400. Yesterday I washed and reoiled the K&N air filter. Being the first time I've cleaned it, I accidentlly oiled it too much. Today I went for a ride and got a fill up of plus at Shell. Immediatly afterwards, I've noticed that the needle was jumping around when the car was completly stopped. It even stalled once. I went home and noticed that some oil was dripping. I rewashed and reoiled the K&N filer this time with light oil. It seemed to behave correctly when I was driving until later, when the exact symptoms started happening.

Did I get oil into the air intake system? Or is it bad fuel? If it did get into the air intake system, how do I flush it out?

Thanks

[maniek_LS]

Did I get oil into the air intake system? Or is it bad fuel?

1. check if MAF sensor is clear

2. check air pipe from MAF to throttle - if it clear don't search more - add new gasoline with better octane value

3. if you find oil in the air pipe check/clear ICV valve (located at front of engine) this part is responsible for idle.

[Ross W.]

In addition to the previous reply, check the connection of the wiring harness to the m.a.f. sensor. When I clean my filter, I disconnect that connector because I found the harness to be stressed when removing the filter. And like the previous reply, definitely look inside the m.a.f. assembly. The Lexus design is an optical one, not a hot-wire type, so if oil gets on the optics, that could definitely cause problems. I don't know if it's safe to clean the optics or not. There are two probes that come down from the roof of the housing, and that's where the optics live. One probe has a reference light and the other is the sensor.

Hope this helps!

[zlilz]

The MAF seemes clean, but I was afraid to touch it. I've noticed the problem only occures when the engine is at normal temperature and has been running for a bit. I'll check the airpipe but seeing how oil free the MAF is, I doubt i'll find something.

When cleaning the air filter, I did remote the wiring harness. I plugged it back in though. Could some dirt have gotten into the connectors and is creating a bad connection only when the engine is at normal temperature?

[Ross W.]

The MAF seemes clean, but I was afraid to touch it. I've noticed the problem only occures when the engine is at normal temperature and has been running for a bit. I'll check the airpipe but seeing how oil free the MAF is, I doubt i'll find something.

When cleaning the air filter, I did remote the wiring harness. I plugged it back in though. Could some dirt have gotten into the connectors and is creating a bad connection only when the engine is at normal temperature?

It would take a pretty major chunk of dirt to do that, enough that it would probably feel a little tight or strange when re-connecting. I think what you're experiencing is coincedental to what you did. Sounds like the main coolant temp sender for the computer has gone bad. I think Lexus used redundant sensors for both the dash guage and the ECU. Check to see if there are any fault codes stored in the ECU at this point.

[mikeythewop]

When using oiled airfilters such as K&N, over time, or if over-oiled, a residue builds up on the Mass Air flow sensor directly aft of the filter. It will cause eratic signals to be sent to the ECU, which results in altered fuel delivery (usually "lean" due to a reading indicating lack of intake air). Sounds scientific and *BLEEP*, however you only need to remove the filter and MAF senor, follow the K&N washing/oiling instructions, and use MAF sensor cleaner (aerosol can) without touching the sensor with oily fingers or any foreign object. problem solved.