westopill

So I have some new issues with my 94 LS (172000 miles) lately. When I'm in cruise mode and I put my turn signal on the RPM jumps up to 4000 without changing the speed, which I find interesting. It's a little frightening on the highway, but like I said, the speed doesn't change. I will link a video I took of this happening below. As you can see in the vid, the blinker doesn't turn on in the dash, but the "headlight on" indicator flashes instead. This seems like a wiring issue to me, but could this also be an alternator or ECU issue as well?

CELSI0R

It looks like your instrument cluster or some of the wiring to it may be faulty.

The tachometer needle's movements look too artificial, and I could not hear a difference in the sound of the engine when you turned your blinker on. If the car did rev to 4000 rpm, the speed would have changed too. Also, your turn signal indicators are not lighting up on the dash, and your parking lights indicator is blinking instead.

I would run a few tests with the car sitting idle at home to see if you can trigger the same kinds of events while the car is not moving. This may include switching on the turn signals, hazard lights, high beams, low beams, fog lights, parking lights, and changing between the odometer and trip meters. You can try this with the car on and off.

Also, try to duplicate what happened while the car is not moving. If you had the headlights on, turn them on with the turn signal and cruise control and see if the tachometer goes wild.

Here are some pages from the Owner's Manual on the instrument cluster's functionality:
http://drivers.lexus.com/t3Portal/do...4U/pdf/1-3.pdf

More here:
https://secure.drivers.lexus.com/lex...r=1993&type=om

westopill

I'm not so sure it's the instrument cluster that's the issue. I can feel the car shift into lower gear when this happens. It also happens even when I'm not in cruise mode and I put on my right turn signal. My left turn signal doesn't trigger the RPM change. I recently swapped my reverse lights to LED, so I'll see if that's the issue.

CELSI0R

That sounds like a good plan. Just for the record, was this happening before you changed the lights to LEDs? Also, which of your lights are LEDs and which are still regular bulbs?

I would still test out your cluster at home to see if it acts strangely even when the car is not moving.

westopill

I tested it while I was parked and nothing was out of the ordinary. Before installing LED back up lights I had issues as well. One of those issues being that when I shift into reverse with my lights on, the right blinker indicator turns on and stays lit until I shift into drive. It has to be a wiring issue with the blinker indicator, reverse, and the headlight indicator, but I don't really know where to start on that. I think the reverse light wiring harness is a good place to start. I checked the trunk wiring harness that this site refers to: http://www.lexls.com/tutorials/lighting/bulbout.html but I couldn't find any issues or bare wire. I'll put the regular bulbs back in tonight and see if that takes care of this new issue I'm having.

westopill

Well, I installed the old non LED bulbs in, and problem solved. I still have issues with the reverse light and blinker, but no more RPM issues. I took the time to make this video on the issue so you can see first hand what is going on.