1990 Ls400 Electrical Problems

[Rob En Cognito]

I don't know if these are related but...

Yesterday I noticed that when I used my turn signal or rolled down a window the signal to the radio would go out for a just a second. The power to the radio appears to be continuous but the signal is cut. This happens on any radio station and can be replicated with at least those two things (Use of Window or Turn Signal)

More troubling was tonight on the way home I noticed that my throttle was "stuck" as I drove down the Freeway. What ever speed I accelerated to if I took my foot off the gas it would maintain this speed. I could come to a stop but if I took foot off break while at a speed it would maintain that speed. I pulled into a parking lot and put the car into park and noticed that the engine was reving itself. The Tach would rev up to 3K and then drop back down to 1K. This also happens in Neutral. If I put it in drive, it will idle somewhat normally and it drives as fine otherwise.

I looked all over the net and this board and I noticed that some electrical problems are caused by the power steering pump leaking on the alternator. I had a power steering leak a few months back and had it fixed. I hadn't had any problem since then though, until now. Obviously, tomorrow I will call the mechanic and I will take it and get the codes checked out at hi-lo but I thought I might see if this problem sounds like something that has happened to any of you.

My car has about 120K miles on it and has been keep incredibly well. 1 owner before me and I have records of every single thing that has ever been replaced. Let me know if more info is needed.

Thanks in advanced, at least the problem let me find this board, nice to find other LS400 owners.

Rob

[oldskewel]

I don't know if these are related but...

Yesterday I noticed that when I used my turn signal or rolled down a window the signal to the radio would go out for a just a second. The power to the radio appears to be continuous but the signal is cut. This happens on any radio station and can be replicated with at least those two things (Use of Window or Turn Signal)

More troubling was tonight on the way home I noticed that my throttle was "stuck" as I drove down the Freeway. What ever speed I accelerated to if I took my foot off the gas it would maintain this speed. I could come to a stop but if I took foot off break while at a speed it would maintain that speed. I pulled into a parking lot and put the car into park and noticed that the engine was reving itself. The Tach would rev up to 3K and then drop back down to 1K. This also happens in Neutral. If I put it in drive, it will idle somewhat normally and it drives as fine otherwise.

I looked all over the net and this board and I noticed that some electrical problems are caused by the power steering pump leaking on the alternator. I had a power steering leak a few months back and had it fixed. I hadn't had any problem since then though, until now. Obviously, tomorrow I will call the mechanic and I will take it and get the codes checked out at hi-lo but I thought I might see if this problem sounds like something that has happened to any of you.

My car has about 120K miles on it and has been keep incredibly well. 1 owner before me and I have records of every single thing that has ever been replaced. Let me know if more info is needed.

Thanks in advanced, at least the problem let me find this board, nice to find other LS400 owners.

Rob

Couple of quick ideas before the experts chime in.

- These problems might not be related.

- Any time an electrical problem shows up, it seems that the trunk wiring harness is the first thing to check.

- Regarding the "stuck" throttle, does it really hold _exactly_ 52 mph or 73 mph or whatever (as cruise control would), or does it just hold the approximate speed for a little while? My thought on the auto-revving when in park (based on other cars I've had) is that it could be caused by the Idle Air Control Valve (not sure the Lexus calls it this) sticking. These are often near the throttle body. You can try to see if tapping it with a wrench while it is revving changes the revving (e.g., stops it). If so, it may be ~clogged internally, and the tapping allows it to move. In both cases I've had with this problem, I've found that simply removing the IAC valve and cleaning it out (no need to disassemble it) with brake cleaner (any similar solvent should work) fixed it.

Good luck, Ed

[oldskewel]

One more thing ... Welcome to the club!

[Rob En Cognito]

I don't know if these are related but...

Yesterday I noticed that when I used my turn signal or rolled down a window the signal to the radio would go out for a just a second. The power to the radio appears to be continuous but the signal is cut. This happens on any radio station and can be replicated with at least those two things (Use of Window or Turn Signal)

More troubling was tonight on the way home I noticed that my throttle was "stuck" as I drove down the Freeway. What ever speed I accelerated to if I took my foot off the gas it would maintain this speed. I could come to a stop but if I took foot off break while at a speed it would maintain that speed. I pulled into a parking lot and put the car into park and noticed that the engine was reving itself. The Tach would rev up to 3K and then drop back down to 1K. This also happens in Neutral. If I put it in drive, it will idle somewhat normally and it drives as fine otherwise.

I looked all over the net and this board and I noticed that some electrical problems are caused by the power steering pump leaking on the alternator. I had a power steering leak a few months back and had it fixed. I hadn't had any problem since then though, until now. Obviously, tomorrow I will call the mechanic and I will take it and get the codes checked out at hi-lo but I thought I might see if this problem sounds like something that has happened to any of you.

My car has about 120K miles on it and has been keep incredibly well. 1 owner before me and I have records of every single thing that has ever been replaced. Let me know if more info is needed.

Thanks in advanced, at least the problem let me find this board, nice to find other LS400 owners.

Rob

Couple of quick ideas before the experts chime in.

- These problems might not be related.

- Any time an electrical problem shows up, it seems that the trunk wiring harness is the first thing to check.

- Regarding the "stuck" throttle, does it really hold _exactly_ 52 mph or 73 mph or whatever (as cruise control would), or does it just hold the approximate speed for a little while? My thought on the auto-revving when in park (based on other cars I've had) is that it could be caused by the Idle Air Control Valve (not sure the Lexus calls it this) sticking. These are often near the throttle body. You can try to see if tapping it with a wrench while it is revving changes the revving (e.g., stops it). If so, it may be ~clogged internally, and the tapping allows it to move. In both cases I've had with this problem, I've found that simply removing the IAC valve and cleaning it out (no need to disassemble it) with brake cleaner (any similar solvent should work) fixed it.

Good luck, Ed

Thanks for the reply.

From what I could tell it was staying the same speed. In fact the first thing that came to mind was that I was in cruise control, the light wasn't on though, and I even clicked the button to see if it wold stop the problem.

I saw the trunk wiring harness thing on a few threads too, I'll check that out now.

Thanks for the input, any other advise is welcome too.

Rob

[Rob En Cognito]

Well, it died today on the way to School.

Had it towed to my Mechanic and after talking to him he thinks it is either the Alternator or the trunk harness or both. Said the engine reving was probably it trying to produce the electricity it needed to run everything and that the reason the radio would cut out when using something else was because it was not able to run it all at once, so it would steal the electricity from one system to feed the others.

hmm... hope he is right.

[landar]

Did your "ALT" light come on at any time?

[bencho]

I had an alternator problem. Had it replaced and then replaced the battery as well for good measure.

Symptoms were very clear for me. Lights dimmed and the radio produced a lot of static and then everything powered down. Never had the window problem though. Should check that power steering leak over the alternator!*

[eatingupblacktop]

Sounds like you're not getting enough voltage to run the electrical systems. Load test the alt and the batt.